bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Intercropping Maize or Sorghum with Cowpeas, Pigeon Peas or Beans
Authors: Enyi B. A. C.
Published: October 2008

Intercropping maize or sorghum with pigeon peas, cowpeas or beans led to a reduction in leaf area indices, fresh weight yield at time of anthesis, straw yield at harvest and grain yield of the cereal crops. In sorghum, pigeon peas and cowpeas had a greater adverse effect on grain yield than beans, but with maize, beans and cowpeas had a more adverse effect on grain yield than pigeon peas. While intercropping maize with either beans or cowpeas decreased total yield of grain (cereal and legume) per hectare, intercropping sorghum with pigeon peas increased total grain yield per hectare.
Towards the Reliable Prediction of Time to Flowering in Six Annual Crops. III. Cowpea Vigna unguiculata
Authors: Ellis R. H. , Lawn R. J. , Summerfield R. J. , Qi A. , Roberts E. H. , Chay P. M. , Brouwer J. B. , Rose J. L. , Yeates S. J.
Published: October 2008

Six genotypes of cowpea (Vigna unguiculata) of diverse origin were sown on various dates at five locations in Australia in order to provide a range of photothermal environments. Times from sowing to first flowering (f) ranged between 36 d and 145 d; pre-flowering temperature and photoperiod means varied from 15.7° to 29.2°C and from 11.6 to 15.5 h d−1. In five genotypes there was no effect of photoperiod on rate of progress towards flowering (1/f), but the relation between 1/f and mean temperature was always positive. The base temperatures (at which 1/f = 0) varied between 8.1° and 10.4°C. The rankings of parameter estimates among four photoperiod-insensitive genotypes common to this study and earlier research in controlled environments were almost identical, and there was generally good agreement between field observations and predictions from controlled environments once hourly temperatures were used to describe the natural environment. When cowpea plants were exposed to temperatures below 3°C, flowering was delayed beyond expected values, presumably as a result of chilling damage. In one genotype, rate of progress towards flowering was affected by both temperature and photoperiod, and relations between 1/f and the photothermal environment were described by a two-plane linear model of similar form to that determined in an earlier controlled environment study. These latest findings support the utility of such linear models for the prediction of crop phenology in the field and for the genetic characterization of photothermal flowering response in annual crops.
The Effect of Tillage on Topsoil Temperature and Strength in Coarse-grained Sands with Special Reference to a Tied Ridging System
Authors: Vogel H.
Published: October 2008

Tillage trials on sandy soils in Zimbabwe have shown that sheet erosion from arable fields under a no-till tied ridging treatment is negligible but that the system generates environmental conditions that have an adverse effect on crop potential. Tied ridging improves crop production by preventing waterlogging in high rainfall years and improving rooting depth when adequate water supply prevents soils from setting hard, but it causes high temperatures in the ridges and rapid drying during dry weather, resulting in poor or delayed emergence and thus in low and uneven crop stands. New strategies need to be developed to minimize these effects.
The Effects of Sole and Traditional Intercropping of Millet and Cowpea on Soil and Crop Productivity
Authors: Reddy K. C. , Visser P. L. , Klaij M. C. , Renard C.
Published: October 2008

The after effects of three years' continuous cropping with sole millet, sole cowpea or a traditional millet/cowpea intercrop were compared using five levels of nitrogen fertilizer. The continuous sole cowpea system had reduced the carbon to nitrogen ratio more than the continuous sole millet or the traditional intercrop. The test crop millet yielded much more, and its uptake of nitrogen and phosphorus was greater, when it followed sole cowpea than when it followed sole millet or the traditional millet/cowpea intercrop. The three years' continuous sole cowpea had an effect equivalent to the application of 205 kg N ha−1on the test crop of millet. It also caused the greatest reduction inStrigainfestation in the test crop. It is therefore recommended that cowpea cultivation be increased in the Sahel.
Influence of Tree Training and Plant Density on Yields of an Improved Cultivar of Coffea arabica
Authors: Njoroge J. M. , Kimemia J. K.
Published: October 2008

The effect on Coffea arabica cv. Ruiru 11 of training the trees on a single or two stem system at planting densities of between 1600 and 4800 trees ha−1 during the first production cycle after establishment was studied at three contrasting sites in Kenya. Training tree growth in the two stem system significantly depressed yields from the first two crops at all sites, irrespective of plant density, but yields caught up with the production levels of the single stem system faster in the wetter than in the drier zone. Yields of clean coffee increased with tree density up to 4000 trees ha−1 at all sites, irrespective of tree training method, but increased more slowly at populations of more than 4000 trees ha−1, especially in the drier zone. The proportion of large, grade A, coffee beans was not significantly influenced by the treatments studied.
Propagating Cassava (Manihot esculenta) by Sexual Seed
Authors: Iglesias Carlos , Hershey Clair , Calle Fernando , Bolaños Ana
Published: October 2008

Commercial cassava production from true cassava seeds (TCS) appears to be a promising option for reducing or eliminating several of the production constraints associated with vegetative propagation. The most important contribution of TCS would be to reduce virus build-up in vegetative material and to resolve the problems of stake storage, low multiplication rate and the long growth cycle. Preliminary results suggest that the root yield potential of TCS is comparable with that of traditional vegetative propagation. Improvements in the capacity of true seed progenies to germinate and establish in the field can be achieved either genetically or through pre-planting seed treatments such as coating the seed with rock phosphate. Development of a successful TCS technology will require a multidisciplinary approach, involving basic studies in cassava breeding, physiology, agronomy, socio-economics and other fields.
Unpacking a Technical Package: Flexible Messages for Dynamic Situations
Authors: Okali C. , Sumberg J. E. , Reddy K. C.
Published: October 2008

This paper describes an attempt to develop and evaluate agricultural extension materials that support farmers' use of flexible management strategies. On the basis of experiment station and on-farm research results relating to millet and cowpea intercropping in Niger, a series of recommendations was developed, taking the form of a decision tree. The process of testing this format at the level of field extension agents and the implications of this experience for both research and extension workers are described.
Forage Yield of Sorghum and Winter Clovers as Affected by Biological and Chemical Reclamation of a Highly Alkaline Soil
Authors: Kumar Ashok , Batra Lalita , Chhabra R.
Published: October 2008

A field experiment was conducted on a highly alkaline soil (pH 10.6, exchangeable sodium 95%) to compare biological reclamation using Leptochloa fusca with chemical reclamation using gypsum. Rice gave satisfactory yields in the first year of gypsum application but sorghum and Sesbania gave extremely poor yields. The yield of Leptochloa was not affected by gypsum application. Trifolium resupinatum yielded more than T. alexandrinum when sown in the winter season. The green forage yield of sorghum was greatest when the sorghum followed Leptochloa grown for two years, with the harvested grass allowed to decompose on the site. The results show that biological reclamation with Leptochloa is a good substitute for chemical reclamation with gypsum.
Sink-Source Relations in Cassava: Effects of Reciprocal Grafting on Yield and Leaf Photosynthesis
Authors: Pellet Didier , El-Sharkawy Mabrouk A.
Published: October 2008

Two contrasting clones of cassava (Manihot esculenta) were reciprocally grafted to test the hypothesis that the yield of cassava is limited by the number of storage roots. Effects of the root sink on leaf gas exchange were also tested under field conditions using a portable infra-red gas analyzer. Storage root number and root yield were affected by stock size and root yield was associated with the number of storage roots. The harvest index and sink-source ratio (root numberz/leaf area index) were correlated with root number. A feedback effect of root number on single-leaf photosynthesis was observed in one clone. It is concluded that the number of storage roots may be used as an indicator of sink strength.
Experimental Agriculture and the Malthusian Challenge
Authors: Arnold M. H.
Published: October 2008

Nearly two hundred years have elapsed since Robert Malthus published (anonymously) his first ‘Essay on the Principle of Population as it Affects the Future Improvement of Society …’. Population, he argued, will always grow faster than the means to sustain it, unless constraints to its growth arise naturally or are imposed artificially.
Editorial Code for Presentation of Statistical Analyses
Authors: Finney D. J. , Harper J. L.
Published: October 2008

The proliferation of statistical methods and software increases the need for authors to state, unambiguously and informatively, the methods they have used. The reader of any paper should expect to learn precisely what the author has done, and to be able to adopt similar procedures in his or her own work.
Weeds and Weed Control in Coffee
Authors: Njoroge J. M.
Published: October 2008

The effects of weeds on coffee productivity and the methods used for their control are discussed. The more common weeds are listed, together with the control methods that can be used at various phases of coffee production.

Malezas y control de las mismas en el café
The Water Relations of Barley Grown Continually or After Fallow Under Semi-Arid Conditions
Authors: Orphanos P. I. , Metochis C.
Published: October 2008

Grain barley was grown either continually or in rotation with fallow in a 12-year experiment. Annual rainfall ranged from 120 to 297 mm. As the water requirement of the crop is 240 mm, growth in most seasons occurred under water stress. The amount of water conserved under fallow was only significant (75–100 mm) in three of the 12 years and only once did the water conserved increase barley yield in the following year. The total grain yield over the experimental period was twice as high in the barley–barley sequence as in the barley–fallow sequence.

Cultiuo continuo de cebada o después de barbecho
Problems and Perspectives on the Use of a Crop Simulation Model in an African Research Station
Authors: Mbabaliye T. , Wojtkowski P. A.
Published: October 2008

Crop simulation models have been proposed as tools for the transfer of technology in less developed countries. Using a validation exercise as a framework for evaluation, this study looked at the ease of use of a simulation model in a small African research station. Although the model did not accurately predict grain yield of the local maize hybrid, the procedure did highlight some of the problems involved in applying the model. The constraints to the use of such models at small research stations are discussed and improvements that could facilitate model use are suggested.

Uso de model de cultivo para la investigación en Africa
Influence of Nitrogen Application and Stage of Harvesting on the Dry Matter Production of Sorghum Sudanense-Lablab purpureus Mixtures in Central Sudan
Authors: Ibrahim A. E. S.
Published: October 2008

The effects of cropping system, nitrogen application and harvesting stage on the quantity and quality of the forage produced by Sudan grass-lablab mixtures were studied in central Sudan. Mixing increased the number of tillers plant-1 of Sudan grass and the plant dry weight of both crops. Application of nitrogen increased the number of tillers and dry weight plant-1 of Sudan grass but had no significant effect on the growth parameters of lablab. Growth parameters of both crops were appreciably increased by harvesting at the milk-ripe stage of Sudan grass. The largest total dry matter yield was obtained from a mixture of 20 kg Sudan grass and 40 kg lablab ha-l, but the largest protein yield was obtained from sole lablab.

Nitrógeno en combinaciones de sorgo sudanés y Lablab purpureus
Development of Leaves in Oil Palm (Elaeis Guineensis) and Determination of Leaf Opening Rate
Authors: Breure C. J.
Published: October 2008

Oil palm rachis length was determined on primordia dissected from palms planted at four densities. It started to increase rapidly in leaf–10, that is, about ten leaves younger than the spear leaf in all density treatments. The mean number of leaf primordia at the three higher palm densities was 47.7 compared with 51.5 at the lowest density of 56 palms ha-1. Some of the palms planted at the highest density were thinned to identify the stage at which the amount of light affected the rate of leaf opening. A sudden increment of light accelerated leaf production at both the rapid expansion stage and the preceding slow expansion stage. The greatest acceleration of leaf production began 24 months after thinning, probably because of the effect of the extra light on the rate of leaf initiation. The response of leaf production to thinning may apply to other related cultural practices.

Desarrollo de hojas en la palma aceitera(Elaeis guineensis)y determination de la tasa de apertura de las hojas
Evapotranspiration of Onion in Sahelian Niger
Authors: Prashar Chit R. K. , Sharma Govind C. , Gandah Mohamadou
Published: October 2008

Irrigation responses of three locally adapted onion cultivars were studied in drainage type lysimeters and under field conditions on a deep sandy loam soil, free of salinity problems, at Maradi in Niger. Evapotranspiration (Et) was established by the water balance method, and used to establish the rate of water use. The peak rate of water use was 7.5 mm per day during the bulb formation stage. Irrigating onions when the available soil moisture to a depth of 20 cm had been depleted by 40% increased the yield more than irrigation at 60 or 80% depletion. The mean yield from plots receiving frequent irrigation was 33 t ha−1.

Evapotranspiratión de la cebolla en el sahel nigeriano
Selection of Dry Pea (Pisum Sativum) Varieties and their Performance by Comparison with Barley and Wheat in Mediterranean Environments
Authors: Hadjicristodoulou A.
Published: October 2008

The possibility of growing dry peas in the semi-arid areas of Mediterranean countries was assessed by comparing dry pea (Pisum sativum L.) varieties with the highest yielding barley and durum wheat varieties under rainfed conditions and with supplementary irrigation in Cyprus. The yield of barley cv. Kantara was greater than that of the best pea variety selected, PS 210713, especially under the driest conditions, but the differences between cereals and dry pea varieties were smaller when grown in areas where there was more rain or where supplementary irrigation was supplied. The protein content of the dry seeds and straw of the peas was higher than those of the cereals. It is concluded that selected varieties of dry peas could be grown in dry Mediterranean areas, particularly in rotation with barley or wheat.

Pisum sativum L. para zonas mediterráneas
Non-destructive Measurements of Biomass in Millet, Cowpea, Groundnut, Weeds and Grass Swards using Reflectance, and their Application for Growth Analysis
Authors: Buerkert A. , Lawrence P. R. , Williams J. H. , Marschner H.
Published: October 2008

A simple hand-held reflectometer was used to estimate the shoot dry matter of pearl millet (Pennisetum glaucum), groundnut (Arachis hypogaea), cowpea (Vigna unguiculata), weeds and grass swards non-destructively. While the instrument was able to predict shoot dry matter well for single, standing millet and cowpea plants and proved useful for a growth analysis of millet, its reliability was unsatisfactory for groundnut. For millet, the slope of two separate regressions between the difference of reflectance ratios and shoot dry matter, taken 10 days apart, was almost identical. This suggests a possible simplification in future crop growth models. The usefulness of the instrument for estimating dry matter in natural species mixtures such as weeds and grasses depended on the homogeneity of the mixture and the uniformity of their physiological state.

Medición de la biomasa utilizando la reflexión
Response of Azolla Caroliniana and Rice to Phosphorus Enrichment of the Azolla Inoculum and Phosphorus Fertilization During Intercropping
Authors: Singh D. P. , Singh P. K.
Published: October 2008

The effects of phosphorus enrichment of Azolla inoculum and phosphorus fertilization during intercropping on the growth, nitrogen fixation and phosphorus content of Azolla caroliniana and the grain yield, straw yield and nitrogen uptake of rice were studied for four consecutive seasons. The phosphorus-enriched Azolla maintained a higher plant phosphorus content and produced a greater biomass and nitrogen yield than the unenriched Azolla. Application of phosphorus during intercropping significantly increased the dry weight, nitrogen yield and phosphorus content of both unenriched and phosphorus-enriched Azolla. The differences between the enriched and unenriched Azolla declined as increasing levels of phosphorus were applied during intercropping. The grain and straw yields and nitrogen uptake of rice were increased both by phosphorus-enrichment of Azolla inoculum and by phosphorus fertilization during intercropping.

La gestión de fósforos para la siembra simultánea del Azolla y el arroz
Sensitivity (Stability) Analysis of Multiple Variety Trials, with Special Reference to Data Expressed as Proportions or Percentages
Authors: Dyke G. V. , Lane P. W. , Jenkyn J. F.
Published: October 2008

The literature on ‘stability analysis’, which is better called ‘sensitivity analysis’, leaves much to be desired. This paper attempts to clarify the issues, particularly the effect of the non-linearity of the standard model relating variety yields to mean yields over sites. The model is extended from its original applications in the analysis of crop yields to the analysis of measurements that cannot be considered Normally distributed, such as disease assessments expressed as percentages or proportions. Modern computer software offers a method that is theoretically sound and can be applied routinely to data of many different distributional types. Graphical methods of displaying the results of the analysis of non-Normal data are discussed.

Análisis de la sensibilidad de ensayos con variedades
Towards the Reliable Prediction of Time to Flowering in Six Annual Crops. VI. Applications in Crop Improvement
Authors: Lawn R. J. , Summerfield R. J. , Ellis R. H. , Qi A. , Roberts E. H. , Chay P. M. , Brouwer J. B. , Rose J. L. , Yeates S. J.
Published: October 2008

Variation in time from sowing to flowering (f) was examined for 44 cultivars of soyabean, mungbean, black gram, ricebean, cowpea, chickpea, lentil and barley, when grown in up to 21 diverse environments obtained by making one or more sowings at each of six locations spanning tropical, sub-tropical and temperate climates in Australia. The utility of simple linear models, relating rate of development (l/f) towards flowering to mean photoperiod and temperature prevailing between sowing and flowering, was evaluated. The models were highly efficient, explaining most (86.7%) of the variation observed across species, cultivars and environments. They were particularly efficient in describing responses where cultivars were relatively well-adapted, in agronomic terms, and least efficient where cultivars were exposed to unfavourable temperature and, to a lesser extent, photoperiod. Opportunities for exploiting the models in applied crop improvement include their use in interpretation of G × E interaction, genotypic characterization and selection of parental genotypes, selection of test environments, designing screening procedures, and more efficiently matching genotypes to target environments. The main strengths of these linear, additive rate models in crop improvement are their wide applicability across species and genotypes, their relative simplicity, and the requirement for few genotype-specific response parameters. Their main weakness is their lack of precision in describing responses when plants are exposed to unfavourable photothermal extremes, albeit in circumstances that are sometimes unrealistic for cropping those particular genotypes.

Predicciones del tiempo que ha de transcurrir hanta la floración. VI.
Analysis of Water Budgets in Semi-Arid Lands from Soil Water Records
Authors: Pilbeam C. J. , Daamen C. C. , Simmonds L. P.
Published: October 2008

Four components of the water budget for a growing season, namely storage, drainage, transpiration and direct evaporation from the soil surface, were estimated using a suite of techniques. The only data requirements were rainfall, neutron probe measurements of soil water content and microlysimeter measurements of evaporation from the soil. Data from four growing seasons at Kiboko, Kenya between 1990 and 1992 were used to provide examples of the estimations. Drainage was significant (about 10% of rainfall) in one season only; in the other seasons, total evaporation comprised at least 95% of the seasonal rainfall.

Drainage was determined using a relationship between unsaturated hydraulic conductivity and soil water content that was determined during the early part of the rainy season when water was penetrating to depth. This analysis made it possible to identify a critical water content at the base of the soil profile, above which there would be significant drainage. However, there are large errors associated with estimation of drainage if significant drainage occurs.

Estimates of direct evaporation from the soil surface were used as the basis of distinguishing transpiration from total evaporation. Microlysimetry was used to develop a model of evaporation from these sandy soils, which was based on the assumption that the evaporation from the soil surface following heavy rainfall is a unique function of time from rainfall, and little influenced by the presence of a sparse crop. This method showed that direct evaporation from the soil accounted for between 70 and 85% of total evaporation in seasons when total evaporation estimates ranged from 150 to 325 mm.
Yield Gain and Risk Minimization in Maize (Zea Mays) through Cultivar Mixtures in Semi-arid Zones of the Rift Valley in Ethiopia
Authors: Tilahun Amede
Published: October 2008

The effect of mixtures of cultivars on yield and risk distribution in four maize cultivars grown at four different population levels was studied in semi-arid environments in Ethiopia. Mixtures yielded between 2 and 29% more than the pure stands, but late maturing pure stands produced more biomass than mixtures. Mixtures of cultivars with similar flowering periods yielded 60% more than the pure stands in dry growing seasons, but only 30% more when there was more rain. Yield gain was associated mainly with varietal synchrony of anthesis and silking. Mixtures composed of cultivars with different flowering times were less at risk from yield loss in the case of end-of-season drought and yielded 100% more than their late flowering component in pure stand. But in long growing seasons, with an early dry spell, pure stands of the late cultivar outyielded the mixtures whereas pure stands of the early flowering cultivars yielded less than the mixtures, except in years with a serious end-of-season drought. The results indicate that it would be profitable to grow mixtures in semi-arid regions if cultivars with similar height and synchronized flowering time were grown at populations of between 65 000 and 90 000 plants ha−1.
Effects of Defoliation on Sex Differentiation in Oil Palm Clones
Authors: Corley R. H. V. , Ng M. , Donough C. R.
Published: October 2008

Defoliation affected inflorescence production by oil palms, causing a decrease in sex ratio (ratio of female inflorescences to total) and an increase in abortion rate. Clones differed in response to defoliation. One of seven clones showed no increase in abortion rate; in one clone there was a tendency for female inflorescences to abort in greater numbers than males. The change in sex ratio occurred much sooner after defoliation in some clones than in others, and comparison of flowering records with dissections done at the time of defoliation indicated that inflorescence sex was affected at more than one stage in development. This has important consequences for attempts to predict yields.
A Novel System of Tossa Jute (Corchorus Olitorius) Husbandry for Seed, Vegetables and Fuelwood
Authors: Asaduzzaman S. M. , Bright G. , Brook R. M. , Hussain M. A.
Published: October 2008

The implications of a novel system of seed production for tossa jute (Corchorus olitorius), involving late sowing and intercropping with vegetables, were studied in 1989 and 1990. The greatest jute seed yield was obtained from jute-radish intercropping, where radish yielded 12–13 t ha−1 roots and gave the highest average gross margin, although jute-amaranthus intercropping performed marginally better in 1989. This system of husbandry yielded 3–4 t ha−1 of jute stick for fuelwood, which is of great value to rural households, and proved to be a viable means of producing jute seed, vegetables and fuel.
Application of a Maize Crop Simulation Model in the Central Region of Malawi
Authors: Thornton P. K. , Saka A. R. , Singh U. , Kumwenda J. D. T. , Brink J. E. , Dent J. B.
Published: October 2008

A computer crop simulation model of the growth and development of maize was validated using data sets obtained from field experiments run at various sites in the mid-altitude maize zone of central Malawi between 1989 and 1992. The model was used to provide information concerning management options such as the timing and quantity of nitrogen fertilizer applications and to quantify the weather-related risks of maize production in the region. It was linked to a Geographic Information System to provide information at a regional level that could ultimately be of value to policy makers and research and extension personnel.
On Farm Grass-Legume Pasture Performance in the Peruvian Rainforest
Authors: Reátegui K. , Vera R. R. , Loker W. L. , Vásquez M.
Published: October 2008

The possible use of tropical forage legumes in pastures based on Brachiaria decumbens and Andropogon gayanus pastures was tested on farms in the humid tropics region of Pucallpa, Perú. The pastures were established by farmers using manual labour. They were associated with maize in some cases and were normally grown without fertilizers. The pastures were established in areas where fallow regrowth was felled and burnt. These pastures, with grass-alone controls, were incorporated by farmers into their normal paddock rotation and were grazed by dual-purpose cows. Despite the variable terrain and soil conditions, all the pastures established and persisted well. Over a four year period under grazing, the legume contribution to the forage averaged 21% and ranged between 1 and 66%. Desmodium ovalifolium was the dominant legume in paddocks that were not burnt, whereas in pastures regularly burnt to control weeds it tended to disappear and Stylosanthes guianensis was the main legume present. It is concluded that where farmers ensure the maintenance of adequate levels of forage, grass-legume mixtures are a viable and persistent option even if the pasture is occasionally burnt.
Evaluation of the Dry Bean Model BEANGRO V1.01 for Crop Production Research in a Tropical Environment
Authors: White J. W. , Hoogenboom G. , Jones J. W. , Boote K. J.
Published: October 2008

Microcomputer-based simulation models are increasingly being recommended as multipurpose tools for agricultural research. Use of a model should be conditioned by an evaluation of its performance and understanding of its limitations. This paper evaluates the responses of the process-oriented growth model for dry bean (Phaseolus vulgaris), BEANGRO V1.01, with an emphasis on the factors related to cultivar differences for production in tropical environments. Simulations of seed yield from beans grown under conditions of a known water deficit showed good agreement with observed data. The qualitative response to plant population resembled that of a field trial, and the model showed the expected linear relation between days to maturity and seed yield. Overall, the results suggest that BEANGRO has utility for certain types of agronomic studies, but that improvements are possible, particularly with respect to prediction of phenology.
Enhancing Soil Nitrogen Use and Biological Nitrogen Fixation in Wetland Rice
Authors: Kundu D. K. , Ladha J. K.
Published: October 2008

The limited fossil fuel reserve available for manufacturing fertilizer nitrogen and the adverse effects of continued use of high fertilizer nitrogen doses on the environment call for a more efficient use of indigenous soil nitrogen. This paper presents several ways of enhancing soil nitrogen use in wetland rice. These involve utilizing nitrogen present in the deeper soil layers, increasing soil nitrogen mineralization rate, decreasing the loss of mineralized nitrogen from the rooting zone, and adjusting rice variety, soil flooding, and transplanting time. To sustain nitrogen fertility and productivity of ricelands, however, the original soil nitrogen levels must be maintained through natural resources like recycled crop residues and enhanced biological N2 fixation. Various ways of stimulating biological nitrogen fixation by both indigenous and exogenous agents are discussed. Since enhancement of soil nitrogen use in rice and maintenance of the original nitrogen level in soil by stimulating biological nitrogen fixation have not been examined together in the field, elaborate field experiments should be conducted to assess the impacts of such combined practices on long-term soil nitrogen fertility and productivity.
Some Design Problems in Crop Experimentation. II. Multiple Blocking Systems
Authors: Pearce S. C.
Published: October 2008

This paper describes the construction, usefulness and randomization of several designs for field experiments in which there is more than one set of blocks, namely: (a) row-and-column designs, in which there are two crossing sets of blocks, treatments being applied to the plots formed by their intersections; (b) row-and-column designs in which factors are applied to complete rows or complete columns, that is, criss-cross (or strip-plot) designs; and (c) split-plot designs, in which the plots in a study of one factor are used as blocks in the study of another. All are examples of a wider class of designs, with many ramifications, said to have ‘simple block structure’. It is suggested here that some of the assumptions underlying row-and-column designs are questionable. Some alternative approaches are indicated.
Statistical Adjustment of Maize Grain Yield for Sub-Optimal Plot Stands
Authors: Kamidi R. E.
Published: October 2008

Linear covariance analysis of crop yield data using plot stand as the covariate is not satisfactory when the missing plants are eliminated before maturity. This is because the resulting relationship between yield and plot stand is non-linear. In this paper, a transformation of plot yield data to adjust for sub-optimal stands in circumstances involving interplant competition is examined. A biomathematical derivation and interpretation of the proposed model is provided. An experiment involving two varieties of maize (Zea mays) grown at three locations provided the data used to validate the model. Adjusted genotype mean yield values obtained using the proposed exponential transformation were in agreement with observed values.
A Successful Plant Improvement Programme on Tea (Camellia Sinensis)
Authors: Ellis Rex , Nyirenda H. E.
Published: October 2008

The tea industry in Malawi is the oldest in Africa but in the past had always produced poor quality tea. A plant improvement programme was therefore started in 1956 at the Tea Research Stations in Mulanje. The improvement in made tea quality was assisted by an investigation into the biochemistry of tea fermentation. Early success was obtained with polyclonal seed varieties and the development of clones from field bushes. These were used in cross breeding to produce new progeny clones which are showing a steady improvement in quality and yield. The need for improved yield was recognised as the programme progressed and appropriate selection procedures adopted. Techniques for improved vegetative propagation for field planting, grafting ofseed bearer trees and composite plants were developed. Liaison with the tea industry has been good and all new plantings in southern Africa since about 1975 have been with improved material. The programme is continuing and future prospects are good.
Management of a Continuously Cropped Forest Soil Through Fertilizer Use
Authors: Kwakye P. K. , Dennis E. A. , Asmah A. E.
Published: October 2008

Phosphorus, followed by potassium, were the plant nutrients that most limited yields during the third decade of a long-term fertilizer experiment on groundnut, maize and cassava conducted on an Ultisol in Ghana. Application of sulphate of ammonia significantly decreased soil pH, thus reducing crop yields. Superphosphate or mulch applied alone consistently increased the yields of all three crops. Application of potash increased the yield of cassava throughout the cropping period, but the potash × mulch interaction depressed yields in two of the three cropping seasons. Use of crop rotation, grass mulch and fertilizer, including small amounts of lime, enabled crop yields and soil fertility to be maintained at a fairly high level under continuous cropping.
Response of Wheat to Sewage Sludge Applied Under Two Different Moisture Regimes
Authors: Al-Mustafa W. A. , El-Shall A. A. , Abdallah A. E. , Modaihsh A. S.
Published: October 2008

A field experiment was conducted from 1989 to 1992 to investigate the effect of sewage sludge applications on wheat yield under different irrigation regimes. The sewage sludge was applied at rates equivalent to 0, 20 or 60 t ha-1whenever the available soil moisture reached 30 or 70%. The results showed a significant response in grain yield and its nutrient content with no significant differences between rates of sewage sludge applied. Much higher responses were obtained under the wet than under the dry regime.
Self-Reseeding Pasture Barley for Mediterranean Drylands
Authors: Hadjichristodoulou A.
Published: October 2008

Permanent pastures were successfully established with mixtures of bulks of crosses of Hordeum vulgare ssp. vulgare with ssp.spontaneum (given the name Mia Milia) and with mixtures of natural crosses involving H. vulgare ssp. agriocrithon (given the name Akhera).These crosses were made to exploit the brittle rachis gene of wild barley in order to develop self-reseeding pasture barley. No re-seeding of the pasture was necessary but a light cultivation to cover the seed in the first year of sowing improved plant establishment. No cultivation was necessary in the following years. Genotypes with a tough rachis were rapidly eliminated from the Milia pastures (F2 bulks) because of their poor seed dispersal. Nitrogen and phosphorus fertilizer increased dry matter yield. Levels of seed dormancy in the wild barley were adequate to provide a safeguard against extreme dry weather conditions and other natural hazards. Forage quality was very high, with a crude protein content of 18% and digestible organic matter of 80% in harvested dry matter. Permanent barley pastures that exploit the brittle-rachis gene of indigenous genetic material have considerable potential for increasing the animal-carrying capacity of permanent pastures and marginal cropped lands.
The Use of Manure on Smallholders' Farms in Semi-Arid Eastern Kenya
Authors: Probert M. E. , Okalebo J. R. , Jones R. K.
Published: October 2008

The manure that is returned to croplands each year is an important resource in the subsistence farming systems of eastern Kenya. Measurements on several farms have shown that the manure being used is of very poor quality. Analyses of soil samples from beneath the bomas (small enclosures) where animals are kept indicate that substantial losses of nutrients occur through leaching; ammonia volatilization and denitrification may also be involved. Current practice is to apply the manure at rates that appear to make poor use of this scarce resource. The findings are discussed in terms of what changes to the system may be feasible to reduce losses of nutrients, and to improve the quality of the manure and the effectiveness of its use.
Development in Cowpea (Vigna unguiculata). II. Effect of Temperature and Saturation Deficit on Time to Flowering in Photoperiod-Insensitive Genotypes
Authors: Craufurd P. Q. , Qi A. , Ellis R. H. , Summerfield R. J. , Roberts E. H.
Published: October 2008

Twenty-nine diverse genotypes of cowpea (Vigna unguiculata) were grown in approximately 30 photothermal environments in Nigeria and Niger, with mean temperatures ranging from 19° to 30°C, photoperiods from 10 to 16 h d−1 and saturation deficits from 0.5 to 3.1 kPa. Twelve of these genotypes were insensitive to photoperiod. The time of flowering of these photoperiodinsensitive genotypes showed a similar response to temperature. Time to flowering was also delayed by mean pre-flowering saturation deficits greater than 1.5 kPa. The implications of these responses to temperature and saturation deficit for phenological adaptation in West Africa are discussed.
Yields of Cocoa Clones in Response to Planting Density in Malaysia
Authors: Lockwood G. , Yin Joe Pang Thau
Published: October 2008

Ninety five cocoa clones were tested in Sabah, Malaysia at planting densities of 1096 and 3333 plants ha−1. Analysis of dry bean yields up to 60 months after planting showed that vigorous clones performed better at the lower planting density, some clones of intermediate vigour performed well at both planting densities and some weak clones performed well at high planting density. The conclusion that optimal planting densities are highly variable has significant implications for procedures in clone selection and suggests that the relation between the yield of a clone and its general combining ability will become clearer once planting density is taken into account.
Competition Effects between Leucaena and Maize Grown Simultaneously in an Alley Cropping System in Sub-tropical Australia
Authors: Jeanes K. W. , Gutteridge R. C. , Shelton H. M.
Published: October 2008

A field experiment was conducted to assess the effect of competition between a leucaena hybrid and maize (Zea mays L.) when planted simultaneously in an alley cropping system. The leucaena hybrid (a cross between L. diversifolia and L. leucocephala) was planted at hedgerow spacings of 3 and 5.25 m, while maize was planted in rows 75 cm apart between the hedgerows. The spacing between the leucaena hedgerow and maize was varied by removal of 0, l or 2 rows of maize to give three spacing treatments of 37.5, 75 or 112.5 cm between leucaena and maize. A control plot of leucaena alone was also included in the treatments. The growth and yield of individual maize rows were virtually unaffected by the presence of leucaena, but maize had a significant influence on the growth and yield of leucaena. At full maize canopy development, photosynthetically active radiation reaching the leucaena was reduced in all treatments, resulting in a 75% yield reduction in leucaena at the closest spacing. Overall, maize grain yield reached 10.3 t ha−1 in the continuous maize plots (37.5 cm treatment). This was reduced by up to 40% after removal of two maize rows in the closest leucaena row spacing treatment. The implications of these results for the practical establishment of leucaena hedgerows with a maize crop are discussed.
Response of Young Unirrigated Clonal Tea to Nitrogen Fertilizer
Authors: Malenga N. E. A.
Published: October 2008

The response to nitrogen of four high yielding good quality clones of tea was investigated on fertile virgin soil. The yields of all the clones examined were maintained without additional nitrogen during the first two years after planting but Clone PC 81 responded to nitrogen in the second year after planting. This was the earliest recorded stage at which seedling or clonal tea had responded to nitrogen in Malawi. The other clones examined all responded to nitrogen in the third year after planting, and the yields of all the clones were substantially increased by the higher rates of nitrogen applied in the early years after planting, though the responses to nitrogen differed between seasons.
Simulating Root System Development of Short-duration Pigeonpea
Authors: Ito Gayatri Devi O. , Matsunaga R. , Tobita S. , Rao T. P. , Vidyalakshmi N. , Lee K. K.
Published: October 2008

Length and weight of pigeonpea roots were measured weekly in different soil layers and compared with estimates obtained from a root simulation model using daily climatic data, soil physico-chemical properties and dry matter allocation to roots. Daily moisture content and temperature at different soil depths were well simulated using sub-routines from the CERES-Maize model. Daily allocation of dry matter to roots was calculated from logistic functions fitted to the growth data for shoots and roots. Although root length and weight tended to be underestimated by the model, regressions between measured and simulated root growth were highly significant so that the model could, with a few modifications, be used to predict root system development.
Estimation of Technological Needs and Identification of Problems of Farmers for Formulation of Research and Extension Programmes in Agricultural Entomology
Authors: Sabarathnam Ve. , Vennila S.
Published: October 2008

The most important technological needs and farmers' problems in agricultural entomology were identified by analysis of data collected from farmers in Tamil Nadu, India. This showed that damage due to leaf hoppers in rice was the most important research need and that due to brown plant hoppers in rice was the most important extension problem.
Flowering in Pigeonpea (Cajanus cajan) in Kenya: Responses of Medium- and Late-maturing Genotypes to Location and Date of Sowing
Authors: Omanga P. A. , Summerfield R. J. , Qi A.
Published: October 2008

The effects of temperature and photoperiod on times from sowing to flowering (f) were investigated in medium-and late-maturing pigeonpea (Cajanus cajan). Twelve genotypes were sown in two seasons at seven sites in Kenya, covering latitudes 0–4°S and a wide range of altitudes (50–2000 m), as well as under polythene enclosures constructed at six sites to create warmer temperature regimes (a total of 26 environments). The same genotypes were also sown at monthly intervals and in an artificially extended photoperiod (in the open as well as under polythene) created by incandescent lamps suspended above the plots at Katumani (1°30′S).

Times from sowing to flowering varied from 70 to more than 300 days and were associated with variations in mean pre-flowering values of temperature and photoperiod which ranged from 15.2° to 32.7°C and from 12.6 to 15.0 h d−1. Genotypic variation in f in the most inductive regimes (a mean pre-flowering temperature of 24.3°C for the medium- and 20.8°C for the late-maturing genotypes, combined with a mean pre-flowering photoperiod of 12.6 and 12.8 h d−1) ranged from 70 and 76 days and from 85 to 112 days, respectively. There were no photoperiodic effects on f over the range from 12.6 to 13.1 h d−1, but the artificially extended day delayed flowering, especially in the late-maturing genotypes.

The relation between l/f and the mean pre-flowering temperature was linear below and above an optimum temperature, To. The genotype-specific parameters derived from these thermal linear rate models based on flowering responses in 26 environments closely predicted l/f and therefore f in an independent sequence of monthly sowings. It was thus responses to temperature below and above To and not responses to daylength which modulated flowering throughout the wide range of natural environments tested within this vast country, even in the late-maturing and most photoperiod-sensitive genotypes.
Use of Leptochloa fusca for the Improvement of Salt-Affected Soils
Authors: Kumar Ashok
Published: October 2008

The grass Leptocloa fusca is very useful on salt-affected soils as it can tolerate extremely saline and alkaline conditions, Since its growth is not affected by gypsum application, planting with Leptochloa is a good biological method for the reclamation of alkaline soils. It is also well adapted to the waterlogging encountered on saline and alkaline soils, and improves the soil's physical, chemical and biological properties so that within two or three years many commercial and forage crops can be grown. Leptochloa excretes salts through specialized glands and is therefore reasonably palatable to farm animals. Because of its vigorous growth on alkaline soils it does not allow satisfactory growth of companion trees, especially in the initial years of soil reclamation.
On-Farm Experiments with Sorghum to Assess the Acceptability of New Varieties and Herbicide Treatments
Authors: Debrah Siegfried K. , Sanogo Diakalia , Boadu Fred O.
Published: October 2008

On-farm experiments were used for assessing the processing and food value of four promising sorghum cultivars and the willingness of farmers to pay for the herbicide 2,4-D for controlling the parasitic weed Striga hermonlhica in coarse grains. The active participation of farmers in these experiments was useful in determining the conditions under which the improved sorghum cultivars and the herbicide would be most likely to he adopted by smallholder farmers in southern Mali.
Crop Production in a Variable Environment: A Case Study from Southern Zimbabwe
Authors: Scoones Ian
Published: October 2008

Biophysical and socio-economic variability have several impacts on farmers' cropping strategies in dryland areas of Africa. This study examines data from a communal area in southern Zimbabwe over a seven year period. Variation in the output of different crops, in the pattern of crop mixes, in the diversity of cropping patterns and the level of crop sales is explored. Through contrasts between ecological zones and household wealth status, the analysis helps to explain the range of farm-level risk management strategies employed. Finally, the importance for research and extension approaches of understanding variability, through a differentiated analysis of cropping strategies, is emphasized.
Soil Conservation Effectiveness and Crop Productivity of Forage Legume Intercropping, Contour Grass Barriers and Contour Ridging in Cassava on Andean Hillsides
Authors: Leihner D. E. , Ruppenthal M. , Hilger T. H. , Castillo F. J. A.
Published: October 2008

Soil erosion and the productivity of cassava (Manihot esculenta Crantz) cropping systems, including forage legume intercropping, were monitored under natural rainfall conditions on Inceptisols in southwest Colombia. Trials were conducted over two cropping periods on moderate slopes. The best erosion control and cassava fresh root yields were achieved by sole cropping on contour ridges. Erosion was greater with forage legume intercropping than with cassava sole cropping in the first cropping period but once well established and uniformly distributed, undersown legumes controlled erosion effectively, though yields of cassava were depressed by 40% or more. Dense stands of grass contour barriers decreased erosion to tolerable levels. Lower cassava yields due to reduced cropping area and competition from the grasses could be compensated for by the production of valuable forage and by increasing cassava planting density.