bluuebunny/crossref_metadata_2025 huggingface dataset:
Common Bean Response to Tillage Intensity and Weed Control Strategies
Authors: Alemán Freddy
Published: July 2010

Increased concern about environmental degradation, reduced biodiversity, and high production costs for common bean (Phaseolus vulgarisL.) in Nicaragua have increased farmers’ interest in reduced or no tillage systems in combination with low cost and environmentally friendly weed management. This study examined how tillage and weed control measures affect weed densities and biomass, common bean yield, and net income. Three tillage treatments [no tillage (NT), minimum tillage (MT), and conventional tillage (CT)] and three methods of weed control (mulching, mechanical, and chemical) were evaluated in the same field for 3 yr (1994–1996). Bean canopy height was measured twice during the growing season, and bean yield components were recorded each year. Weed biomass and weed density of monocots and dicots, respectively, were measured 28 and 42 days after sowing (DAS) in each experiment. There was an interaction between years and weed control for both weed density and weed biomass. There was also an interaction between tillage system and weed control system regarding bean yield and net economic benefit. Minimum tillage outyielded NT and CT by 10 and 15% and resulted in an increase in net income that was 23 and 35% greater than NT and CT, respectively. Mechanical and chemical weed control increased yields more than mulching in NT and MT. Mechanical weed control with NT or MT would be sufficient to ensure profitable production of common bean. This practice should be combined with the use of both weeds and preceding crop residues as mulches.
Use of Remote‐Sensing Imagery to Estimate Corn Grain Yield
Authors: Shanahan John F. , Schepers James S. , Francis Dennis D. , Varvel Gary E. , Wilhelm Wallace W. , Tringe James M. , Schlemmer Mike R. , Major David J.
Published: July 2010

Remote sensing—the process of acquiring information about objects from remote platforms such as ground‐based booms, aircraft, or satellites—is a potentially important source of data for site‐specific crop management, providing both spatial and temporal information. Our objective was to use remotely sensed imagery to compare different vegetation indices as a means of assessing canopy variation and its resultant impact on corn (Zea maysL.) grain yield. Treatments consisted of five N rates and four hybrids, which were grown under irrigation near Shelton, NE on a Hord silt loam in 1997 and 1998. Imagery data with 0.5‐m spatial resolution were collected from aircraft on several dates during both seasons using a multispectral, four‐band [blue, green, red, and near‐infrared reflectance] digital camera system. Imagery was imported into a geographical information system (GIS) and then georegistered, converted into reflectance, and used to compute three vegetation indices. Grain yield for each plot was determined at maturity. Results showed that green normalized difference vegetation index (GNDVI) values derived from images acquired during midgrain filling were the most highly correlated with grain yield; maximum correlations were 0.7 and 0.92 in 1997 and 1998, respectively. Normalizing GNDVI and grain yield variability within hybrids improved the correlations in both years, but more dramatic increases were observed in 1997 (0.7 to 0.82) than in 1998 (0.92 to 0.95). This suggested GNDVI acquired during midgrain filling could be used to produce relative yield maps depicting spatial variability in fields, offering a potentially attractive alternative to use of a combine yield monitor.
Critical Compositional Nutrient Indexes for Sweet Corn at Early Growth Stage
Authors: Khiari Lotfi , Parent Léon-Étienne , Tremblay Nicolas
Published: July 2010

It would be instrumental to define nutrient norms from small‐size crop databases at the V4–V6 corn (Zea mays L.) growth stage for in‐season N fertilizer recommendations. Our objective was to derive Compositional Nutrient Diagnosis (CND) and Diagnosis and Recommendation Integrated System (DRIS) nutrient index ranges from a sweet corn database and to relate nutrient concentration and indexes to ear yield. A sweet corn database of 240 observations on commercial yields and N, P, K, Ca, and Mg concentrations in 30‐cm high corn seedlings were divided at random between survey (n = 200) and validation (n = 40) subpopulations. The proportion of low‐yield specimens in the survey population was computed at inflection point of a cubic cumulative variance ratio function and was associated with a chi‐square value (CND r2) of 3.9 that was confirmed in the validation subpopulation. Critical CND nutrient indexes were found to be symmetrical about zero as follows: −0.70 to +0.70 for N, −0.45 to +0.45 for P, −1.14 to +1.14 for K, −0.63 to +0.63 for Ca and Mg, and −1.05 to +1.05 for the residual filling value. Summing squared critical nutrient indexes also gave a CND r2 of 3.9, the minimum CND imbalance index for high‐yield targets (>6.7 Mg ha−1). Nutrient concentration values were little to closely related to CND indexes (R2 = 0.34–0.87). The DRIS and CND indexes were highly related to each other (R2 = 0.91–0.99). For N at V4–V6 growth stage, the CND N index was the most closely related to ear yield.
Plant Materials for Soil Fertility Management in Subhumid Tropical Areas
Authors: Kayuki Kaizzi C. , Wortmann Charles S.
Published: July 2010

Lantana camaraL.,Senna hirsuta(L.) Irwin & Barneby,Tithonia diversifolia(Hemsl.) A. Gray, andAspilia kotschyidu Petit‐Thouars occur naturally in eastern and central Uganda. Trimmings of these species were evaluated for effectiveness in improving soil productivity. The plant trimmings varied for N (13–30 g kg−1), P (1.1–1.8 g kg−1), lignin (11–16%), and polyphenol (1.3–2.5%) concentration. Decomposition rates were higher for incorporation than for surface placement, but placement did not affect maize (Zea maysL.) and bean (Phaseolus vulgarisL.) yield. Decomposition rates were similar for all species with the same placement method. Potassium and Mg were generally mineralized most and least rapidly, respectively, with intermediate rates for N, P, and Ca. Maize and bean yield increased with application of 4 Mg ha−1dry wt. trimmings ofL. camara, S. hirsuta, andT. diversifolia, but only maize eventually responded toA. kotschyiYields per units of N and P applied were more and less, respectively, with inorganic than with organic treatments, but plant trimmings supplied less P than fertilizer. At the end of the trial period, available soil P was more for the full rate of fertilizer than for the mean of the plant materials. CombiningL. camaraand fertilizer, at 50% rates, resulted in an average of 0.22 Mg ha−1more yield than expected from mere additive effects of the organic and inorganic resources. The value of plant materials may be enhanced by balancing nutrient supply with inorganic fertilizers.
Effects of Photoperiod on Growth and Development of Soybean Floral Bud in Different Maturity
Authors: Zhang Lingxiao , Wang Ruifang , Hesketh John D.
Published: July 2010

Growth and development of most soybean [Glycine max (L.) Merr.] plants is sensitive to photoperiod effects. Therefore, it is important to understand and quantify the processes involved. Studies were conducted to determine growing degree days required for growth of the floral bud from initiation to open flower of different maturity groups (MGs) in both field and controlled environments. Eighteen soybean strains, including ‘Clark’ back‐cross near‐isolines differing in maturity, were sown in the field at five different dates in 1992 and 1993. In growth chamber studies, plants of two strains differing in maturity were used and moved to 12−, 14−, and 16‐h daylengths after floral buds were initiated in 12 h. Results from both field and growth chamber studies indicated that planting dates had a significant effect on the thermal requirement for bud growth in the late‐maturing strains used. Shorter photoperiods during the bud growth period accelerated growth rates to open flower. Furthermore, in the growth chamber study, flowering was inhibited under 16‐h daylength in a late‐maturity (MG V) strain when plants were transferred immediately after floral bud initiation (FBI) under 12 h. Plants remaining 8 d after FBI before they were transferred to 16 h were not significantly delayed in flowering. This study indicated that photoperiod length and treatment duration affects soybean FBI and floral bud development in a quantitative way, which resulted in a profound photoperiod response in late maturity‐group soybean under field conditions.
In‐Season Fertilizer Nitrogen Applications for Soybean in Minnesota
Authors: Schmitt Michael A. , Lamb John A. , Randall Gyles W. , Orf James H. , Rehm George W.
Published: July 2010

Predicted physiological factors and a limited number of field studies have resulted in debate regarding the recommendation of in‐season fertilizer N for soybean [Glycine max. (L.) Merrill]. The objective of our research was to evaluate several in‐season N fertilization strategies on soybean seed yield response as well as to measure the effect of fertilizer N additions on late‐season plant N concentrations and accumulation, seed N removal, seed protein, and seed oil composition. The research was conducted at 12 sites in the southern soybean‐growing region of Minnesota in 1998 and 1999. A combination of (i) application time (July vs. August), (ii) placement method (broadcast vs. knifed), and (iii) N source (urea vs. poly‐coated urea) gave five N treatments plus a control at all sites. Seed yield did not respond to the fertilizer N treatments at any of the 12 sites; however, a combined analysis indicated a significant increase (generally less than 0.06 Mg ha−1) from using polymer‐coated urea or applying the urea in August. Herbage dry matter (DM) and herbage N concentrations at the R6 stage were not affected by any of the N fertilizer strategies. Although soybean seed protein was statistically different among the treatments, protein was only increased 0.4 g kg−1. Soybean oil concentration was not affected by fertilizer treatments. In general, polymer‐coated urea, knifed applications, and August applications increased soil NO3–N in the 0‐ to 30‐cm layer at R6 relative to standard urea, broadcast applications, and July applications. Even though in‐season N fertilizer created greater levels of available soil N at all 12 sites during soybean pod filling, seed yield was not improved compared with unfertilized control plots at any site. As a result, the University of Minnesota does not recommended in‐season N fertilizer applications for soybean production.
Evaluation of the LAI‐2000 Plant Canopy Analyzer to Estimate Leaf Area in Manually Defoliated Soybean
Authors: Malone Sean , Herbert D. Ames , Holshouser David L.
Published: July 2010

The LAI‐2000 Plant Canopy Analyzer provides a rapid estimate of leaf area index (LAI), but its accuracy and utility for estimating soybean [Glycine max (L.) Merr.] defoliation is unknown. This study evaluated minimum plot‐size requirements for manually defoliated soybean experiments using the LAI‐2000; compared LAI estimates using the LAI‐2000 with directly determined values for 0, 33, 67, and 100% manual defoliation levels; and compared estimates between two LAI‐2000 detector types having spectral sensitivity differences. The minimum plot size for obtaining accurate indirect estimates of LAI in defoliated canopies (0.89‐m height) with 0.38‐m row centers is six rows by 2.28 m and with 0.91‐m row centers and a canopy height of 0.81 m is four rows by 2 m plus an additional 1‐m defoliated area at the ends of the two middle rows. Indirect measurements of LAI with the wide‐blue detector, which is included on newer LAI‐2000 units, were statistically greater than directly determined values in 10 of 12 comparisons. Measurements with the narrow‐blue detector were the same as directly determined values in three of five comparisons in 1998 and 1999 but were statistically greater in 11 of 12 comparisons in 2000. Estimates with the wide‐blue detector were 9 and 2% greater than those with the narrow‐blue detector in 1999 and 2000, respectively.
Improved Nutritive Value of Kura Clover– and Birdsfoot Trefoil–Grass Mixtures Compared with Grass Monocultures
Authors: Zemenchik Robert A. , Albrecht Kenneth A. , Shaver Randy D.
Published: July 2010

Improved dry matter (DM) production of cool‐season grass monocultures may result from either N fertilization or the addition of legumes such as kura clover (Trifolium ambiguum M. Bieb.) or birdsfoot trefoil (Lotus corniculatus L.). Such improvements could affect forage nutritive value and potential milk production from dairy cattle (Bos taurus). Laboratory estimates of forage nutritive value as well as potential milk production per unit mass and area were compared for six levels of N fertilizer on Kentucky bluegrass (KBG; Poa pratensis L.), smooth bromegrass (SBG; Bromus inermis Leyss.), and orchardgrass (OG; Dactylis glomerata L.) in monoculture or with either kura clover or birdsfoot trefoil in binary mixture with each grass. Experiments managed in a three‐harvest system were conducted from 1994 through 1996 near Arlington and Lancaster, WI. Either legume reduced neutral detergent fiber and acid detergent fiber and increased crude protein when added to grass. These effects increased with greater mixture legume DM proportions. Compared with grass monocultures averaged across years and locations and for any N rate, mixtures had greater potential milk production per megagram of DM and followed KBG > SBG > OG. Similarly, potential milk production per hectare for kura clover–grass mixtures exceeded that of monocultures by at least 49% for KBG and 12% for SBG while birdsfoot trefoil–grass mixtures were greater by at least 28% for KBG and 20% for SBG. Orchardgrass required maximum N rates to match milk production per hectare of the mixtures. Adding either kura clover or birdsfoot trefoil will improve potential milk production of these grasses while reducing reliance on fertilizer N in the North‐Central USA.
Variability in Cotton Fiber Yield, Fiber Quality, and Soil Properties in a Southeastern Coastal Plain
Authors: Johnson Richard M. , Downer Robert G. , Bradow Judith M. , Bauer Philip J. , Sadler E. John
Published: July 2010

To maximize profitability, cotton (Gossypium hirsutumL.) producers must attempt to control the quality of the crop while maximizing yield. The objective of this research was to measure the intrinsic variability present in cotton fiber yield and quality. The 0.5‐ha experimental site was located in a producer's field (Norfolk–Coxville soil association) in Florence, SC, for 2 yr (1996 and 1997). Soil (0–20 cm) and fiber samples (1‐m row) were collected from a regular grid (129.2 by 45.6 m, 7.6‐m interval). Soil properties determined included soil moisture, soil texture, organic matter, pH, Ca, Mg, K, P, and Na. Fiber quality was estimated by the high‐volume instrumentation method and the Advanced Fiber Information System. Fiber strength and elongation were also estimated by the stelometer procedure. All fiber and soils data were analyzed by both nonspatial statistics and geostatistical techniques. Distinct patterns of spatial correlation were observed in soils and fiber yield. These patterns were not equally evident in all fiber properties. Soil pH, soil P, and soil organic matter were correlated with fiber yield and a number of fiber properties, including micronAFIS, immature fiber fraction, fine fiber fraction, cross‐sectional area, and micronaire. Factor analysis of soil properties identified four factors in 1996 and three in 1997. In both years, aCarolina bayfactor and anexchangeable basesfactor were obtained. These factors were not successfully related to fiber yield and quality. Kriged contour maps of soil properties provided useful indicators of fiber yield and quality variation.
Corn–Soybean Rotation Effects on Nitrate Leaching
Authors: Zhu Y. , Fox R. H.
Published: July 2010

Because agricultural production is a primary nonpoint source of NO−3in the nation's waters, a better understanding of the effects of cropping systems on NO−3leaching is required for developing agricultural production practices that reduce NO−3leaching. A 4‐yr experiment was conducted to study the effect of a corn (Zea maysL.)–soybean [Glycine max(L.) Merr.] rotation on NO−3leaching using passive capillary fiberglass wick lysimeters. The experiment had five N rates on corn (0–200 kg N ha−1in 50‐kg increments). Corn was planted in 1997 and 1999, and soybean was planted in 1998 and 2000. The increase of soil residual NO−3–N concentrations in the surface 25 cm of soil after crop harvest was not significant (p= 0.05) when N fertilizer rates applied to corn increased from 0 to 100 kg ha−1but was significant when N rate increased from 100 to 200 kg ha−1in the corn years. The 2‐yr average soil residual NO−3–N concentrations and annual flow‐weighted NO−3–N concentrations in leachate were significantly higher (p= 0.05) in soybean years than in corn years at 0 and 100 kg N ha−1applied to corn, but the differences at the 200 kg N ha−1rate were not significant. The results indicate that at recommended N rates applied to corn in a corn–soybean rotation, NO−3leaching potential is similar for corn and soybean, but at less than 100 kg N ha−1rate, a greater NO−3leaching potential exists under soybean than under corn.
Comparison of Allelopathic Potential of Rice Leaves, Straw, and Hull Extracts on Barnyardgrass
Authors: Chung I. M. , Kim K. H. , Ahn J. K. , Lee S. B. , Kim S. H. , Hahn S. J.
Published: July 2010

The use of rice (Oryza sativa L.) allelopathy for weed control is a new technology in agronomy. A laboratory bioassay using water extracts was conducted to determine the allelopathic potential of rice body parts on seed germination and growth of barnyardgrass (Echinochloa crus‐galli P. Beauv. var. oryzicola Ohwi) and to determine rapid and simple methods for selecting allelopathic rice varieties using genetic characters and phenotypes. In this study, the highest inhibition rate was for ‘Danganeuibangju’ (76.9%) in straw extracts, ‘Dongobyeo’ (74.1%) in the leaves, and ‘Baek’ (31.7%) in the hull. ‘CUBA 65‐v‐58’ (38.6%) had the highest inhibition as a whole (average of leaves, straw, and hull), and there was a higher average inhibitory effect for straw extracts (21.6%) than for hulls (8.2%) and leaves (12.4%). With regard to classification by phenotypic and genetic characteristics, these groups showed a higher inhibitory effect in domestic varieties (14.2%), middle‐maturing varieties (15.3%), varieties of hull color (15.1%), and varieties of awn color (16.0%). These results suggest that rice body parts may be a source of natural herbicides and that it is necessary to develop acceptable selection standards. There may also be genetic variation in rice varieties for their allelopathic potential on barnyardgrass. In the future, it might be possible to develop rice varieties with high allelopathic potential.
Planting Date Influence on Dual‐Purpose Winter Wheat Forage Yield, Grain Yield, and Test Weight
Authors: Hossain Ishrat , Epplin Francis M. , Krenzer Eugene G.
Published: July 2010

The use of winter wheat (Triticum aestivum L.) as a dual‐purpose forage and grain crop is important to the agricultural economies of the Southern Great Plains of the USA. Planting date is an important management factor in determining the economic success of a dual‐purpose winter wheat enterprise. The overall objective of the research reported in this paper is to determine the economic optimal planting date for dual‐purpose winter wheat production. The specific objectives are to determine wheat fall–winter forage yield, wheat grain yield, and wheat test weight response to planting date for dual‐purpose winter wheat production. Field studies were conducted in north central Oklahoma from 1991–1992 through 1999–2000. The impact of alternative planting dates on dual‐purpose wheat fall–winter forage yield, grain yield, and test weight was estimated. Estimated response functions illustrate that delaying the planting date from 10 to 30 September resulted in an 18% increase in expected grain yield, a 68% decrease in expected fall–winter forage yield, and only a 0.5% increase in expected test weight. Optimal planting date is sensitive to the relative value of wheat fall–winter forage and wheat grain, but not sensitive to wheat test weight discount schedules. When the value of wheat forage is high relative to the value of grain, it is more profitable to plant early to increase expected forage yield. Alternatively, when the value of grain is high relative to the value of forage, later planting generates greater net returns.
Rapid Characterization of Organic Resource Quality for Soil and Livestock Management in Tropical Agroecosystems Using Near‐Infrared Spectroscopy
Authors: Shepherd Keith D. , Palm Cheryl A. , Gachengo Catherine N. , Vanlauwe Bernard
Published: July 2010

Organic resources constitute a major source of nutrient inputs to both soils and livestock in smallholder tropical production systems. Determination of resource quality attributes using current laboratory methods is both timely and costly. This study tested visible and near‐infrared (wavelengths from 0.35–2.50 μm) reflectance spectroscopy (NIRS) for rapid prediction of quality attributes for a diverse range of organic resources. A spectral library was constructed for 319 samples of oven‐dried, ground plant material originating from green leaf (186 samples), litter (33), root (25), and stem (21) samples from 83 species including tropical crops and trees used for agroforestry and manure samples (39). Organic resource attributes were calibrated to first‐derivative reflectance using regression trees with stochastic gradient boosting, and screening tests were developed for separating various organic resource quality classes using classification trees. Validationr2values for actual vs. predicted values using a 25% holdout sample were 0.91 for N, 0.90 for total soluble polyphenol, and 0.64 for lignin concentration. Screening tests gave validation prediction efficiencies of 96% for detecting samples with high N concentration, 91% for low total soluble polyphenol, and 86% for low lignin concentration. The spectral screening tests were robust even at small (n= 48) calibrations sample sizes. Screening tests for detecting samples with low or high levels of P, K, Ca, and Mg gave prediction efficiencies of 74 to 92%. Near‐infrared reflectance spectroscopy can be used to rapidly screen organic resource quality. Global spectral calibration libraries should be established for a range of resource quality attributes.
Theory and Practical Application of Heat Pulse to Measure Sap Flow
Authors: Green Steve , Clothier Brent , Jardine Bryan
Published: July 2010

Heat pulse methods can be used for accurate measurements of sap flow in plant stems provided a reliable calibration procedure is used to relate the measured heat pulse velocity to the actual sap flow. This paper reviews the theory underpinning both the compensation and T‐max heat pulse methods that use a linear heater and temperature probes inserted radially into the plant stem. These probes not only disrupt the sap stream, but they also alter the thermal homogeneity of the sapwood in the vicinity of the probes. The degree of disturbance depends on the size and geometry of the probes and the corresponding wound width of the nonconducting sapwood. A two‐dimensional model of heat and water flow was used here to derive appropriate correction factors to account for the influence of both probe thermal properties and flow blockage. Wound width has a large influence on the heat pulse measurements while sensor material appears to have little or no influence. A table of correction factors is presented for both the compensation and T‐max methods. These new correction factors are confirmed by comparing heat pulse measurements in the trunk of a willow (Salix alba L.) and a poplar (Populus deltoides W. Bartram ex Marsh), against actual rates of transpiration determined from measured weight loss of the trees growing in large lysimeters. On a daily basis, both heat pulse measurements were found to be within 5 to 10% of the actual transpiration. The compensation method accurately measured flows close to 2 cm/h. The T‐max method had difficulty resolving any flows slower than about 10 cm/h.
Upscaling and Downscaling—A Regional View of the Soil–Plant–Atmosphere Continuum
Authors: Anderson Martha C. , Kustas William P. , Norman John M.
Published: July 2010

The strength of interaction among soil, plants, and atmosphere depends highly on scale. As the spatial scale of organized soil–plant behavior (e.g., soil drying and/or stomatal closure) increases, so does the influence the land surface has on atmospheric properties and circulations. Counterbalancing this is a system of feedback loops that serve to reduce the sensitivity of surface fluxes to changes in surface conditions. Model upscaling involves capturing land–atmosphere feedbacks and effects of land surface heterogeneity on surface fluxes and atmospheric boundary‐layer dynamics that become operative at progressively larger spatial scales. Conversely, by downscaling, we learn how to appropriately parameterize subgrid‐scale phenomena within large‐scale modeling frameworks. This paper discusses some of the major challenges faced today in properly describing system behavior at regional spatial scales. We focus on a suite of simple biophysical models, tied closely to remote sensing, that work synergistically from canopy to mesoscales. This suite includes a diagnostic regional‐scale model used for routine mapping of flux and moisture conditions across the United States at 10‐km resolution. A related approach disaggregates regional flux estimates to local scales (100–102 m) for comparison with ground‐based measurements or for use in site‐specific agricultural or resource management applications. Coupled with turbulence‐ and mesoscale atmospheric models, the core land surface representation provides means for assimilating remote sensing data into large‐eddy simulations and improving short‐range weather forecasts. This multiscale modeling framework is being utilized in a concerted research effort aimed at identifying scale‐relevant land–atmosphere feedbacks and representing surface heterogeneity efficiently and robustly in regional modeling schemes.
Iron Deficiency of Soybean in the Upper Midwest and Associated Soil Properties
Authors: Hansen N. C. , Schmitt M. A. , Anderson J. E. , Strock J. S.
Published: July 2010

Iron deficiency chlorosis is a common, yield‐limiting condition for soybean [Glycine max(L.) Merr.] grown in areas with high‐pH, calcareous soils. The objectives of this study were to document the extent of chlorosis in an area of the upper Midwest, to understand producers' perceptions and management practices related to Fe deficiency chlorosis, and to investigate the soil properties associated with it. A survey tool evaluated the perceptions of soybean producers in western Minnesota regarding cause, extent, and management of chlorosis. A detailed field study in western Minnesota compared plant attributes and soil properties in severely chlorotic, moderately chlorotic, and nonchlorotic sites. Soybean producers indicated that Fe chlorosis is responsible for substantial yield loss on 24% of their crop even though the majority of the producers selected chlorosis‐resistant varieties. Chlorotic plants had stunted growth and poor nodule development relative to nonchlorotic plants. Compared with nonchlorotic areas, soil in chlorotic areas had greater soil moisture content and concentrations of soluble salts, carbonates, and diethylenetriaminepentaacetic acid (DTPA)‐Cr and had lesser concentrations of DTPA extractable Fe, Mn, Ni, and Cd. Discriminant analysis identified soluble salts, DTPA‐Fe, DTPA‐Cr, and soil moisture content as a set of significant predictors of chlorosis. This set of variables suggests that chlorosis occurs due to multiple stresses and not simply to limited available Fe. For a diagnostic soil test, a combination of DTPA‐Fe and soluble salts predicted chlorosis expression. These observations should be considered in soybean variety screening so that variety tolerance can be matched with specific soil properties.
Quantifying Morphological Stage to Predict the Nutritive Value in Sulla (Hedysarum coronarium L.)
Authors: Borreani Giorgio , Roggero Pier Paolo , Sulas Leonardo , Valente Maria Eugenia
Published: July 2010

A precise prediction of quality of legumes in the field would enable harvests to be conducted at appropriate nutritive composition levels. Our objective was to predict the nutritive value of sulla (Hedysarum coronarium L.) with the codified morphological stage and weather parameters at two Mediterranean sites (Ancona and Sassari, Italy) in 1996, 1997, and 1998. Herbage samples were collected at progressive morphological stages, from vegetative stage to seed setting. Mean stage by weight (MSW), dry matter yield (DMY), leaf/stem ratio (L/S), crude protein concentration (CP), neutral detergent fiber (NDF), gross energy (GE), and organic matter digestibility (OMD) were determined. Forage characteristics were regressed on growing degree days (GDD) and MSW. The DMY ranged from 2 to more than 10 Mg ha−1 from vegetative to seed set while L/S decreased from almost 5.6 to 0.2 and the CP from a maximum of 295 to a minimum of 107 g kg−1 dry matter (DM). The NDF ranged from 200 to 616 g kg−1 DM and was best predicted by L/S and MSW. The GE was relatively constant across growth stages with a mean value of 18.0 MJ kg−1 DM. The OMD ranged from 398 to 846 g kg−1 organic matter (OM) and declined linearly with increasing MSW. The OMD decreased 32.6 g kg−1 OM per stage unit and followed similar trends for the two sites, with a lower level at the warmer site (Sassari). The MSW was a better predictor of sulla OMD than GDD, with a higher R2 (0.70 vs. 0.54) and a lower root mean square error.
Pearl Millet and Grain Sorghum Yield Response to Water Supply in Nebraska
Authors: Maman Nouri , Lyon Drew J. , Mason Stephen C. , Galusha Tom D. , Higgins Rob
Published: July 2010

Pearl millet [Pennisetum glaucum (L.) R. Br.] is a drought‐tolerant crop that may serve as an alternative summer crop in Nebraska. Field experiments were conducted in 2000 and 2001 near Sidney and Mead, NE, to determine the water use efficiency (WUE) and yield response to water supply at critical developmental stages of pearl millet and grain sorghum [Sorghum bicolor (L.) Moench]. Four water regimes were used: (i) no irrigation, (ii) single irrigation at boot stage, (iii) single irrigation at mid–grain fill, and (iv) multiple irrigations. Pearl millet grain yields were 60 to 80% that of grain sorghum. Average grain yields at Mead were 5.1 Mg ha−1 for pearl millet and 6.1 Mg ha−1 for grain sorghum. At Sidney, average pearl millet yields were 1.9 and 3.9 Mg ha−1 in 2000 and 2001, respectively, and average grain sorghum yields were 4.1 and 5.0 Mg ha−1 in 2000 and 2001, respectively. Both crops used a similar amount of water (336 and 330 mm in 2000 and 370 and 374 mm in 2001 for pearl millet and grain sorghum, respectively) and responded to irrigation with a linear increase in grain yield as water use increased. Grain sorghum had greater WUE than pearl millet (12.4–13.4 kg vs. 5.1–10.4 kg grain ha−1 mm−1). Pearl millet, with lower and less stable yields, does not currently have the potential to be a substitute crop for grain sorghum in Nebraska.
Effect of Swine Slurry on Alfalfa Production and on Tissue and Soil Nutrient Concentration
Authors: Lloveras Jaime , Arán Miguel , Villar Pere , Ballesta Astrid , Arcaya Angel , Vilanova Xavier , Delgado Ignacio , Muñoz Fernando
Published: July 2010

Alfalfa (Medicago sativa L.) may not be the most suitable crop to utilize all the manure nutrients, but it may be the best crop available, especially when the crop is dormant. The objective of this research was to investigate the effect of swine (Sus scrofa domesticus) slurry manure on alfalfa yield and the concentration of nutrients in soil. A 2‐yr field experiment was initiated in 2001 on two soils: a Typic Xerofluvent and a Calcixerolic Xerochrept. Soil mineral elements were extracted with ammonium bicarbonate diethylenetriaminepentaacetic acid, and initial extractable P and K were 16.7 and 6 mg P kg−1 and 152 and 103 mg K kg−1 for the two soils, respectively. There were four treatments: annual winter applications of 25 and 50 m3 ha−1 of swine slurry manure, annual fertilization of 32.75 kg P ha−1 and 125 kg K ha−1, and a no‐manure or fertilizer control. Application of slurry manure in winter was not detrimental to the crop. Manure and fertilizer treatments increased alfalfa dry matter (DM) yield 37% on the low‐fertility soil. There was no significant effect of manure or fertilizer on alfalfa DM yield on the Xerofluvent soil. Application of the slurry slightly increased the soil concentrations of P, Mg, Zn, and Fe in higher‐fertility soils and copper in low‐fertility soils. The 2‐yr results suggest that the application of slurry in soils with low levels of trace elements, such as those used in the trials, does not produce a significant buildup of these elements that could lead to an environmental problem.
The Balance Sheet Method as a Conceptual Framework for Nitrogen Fertilization of Wheat in a Pampean Agroecosystem
Authors: Alvarez R. , Steinbach H. S. , Grigera S. M. , Cartier E. , Obregon G. , Torri S. , García R.
Published: July 2010

Yield response curves to fertilizer are needed to determine N rates for wheat (Triticum aestivum L.) in the Argentine Rolling Pampa. Relationships between yield and available N have not been developed for this region. The balance sheet method can be use to define N fertilization strategies when yield data are not available. The shortcoming of this method is that profitability cannot be assessed. This study was conducted to: (i) determine N requirements for wheat in the Rolling Pampa, (ii) develop algorithms for predicting crop available N, and (iii) develop a model for making N fertilizer recommendations. Fifty‐eight field plots were selected with contrasting soil and management conditions. Soil mineral N content and N in residues of preceding crop were determined at initial and harvest stages of wheat from 1997 to 1999. Plant N accumulation was measured, and N mineralized from organic soil pools was calculated using a mass balance approach. Nitrogen available in the mineral and organic soil pools limited N uptake and yield. As available N increased, crop use efficiency and agronomic efficiency decreased. The model prediction agreed well with measured plant N uptake (R2 = 0.82) and explained 51% of yield variability. The model estimated the impact of increasing fertilizer N on yield in soils differing in N mineralization capacity. The economic optimum N requirement in the Rolling Pampa is 140 kg ha−1 for soil having an average capability to supply N from organic pools and at a mean fertilizer price/grain price ratio. This optimum increased or decreased 30 kg ha−1 across the range of N mineralization rates observed. Despite the empirical nature of the algorithms developed, the concepts may be used in other regions where response functions to N are not available.
Sod‐Seeding and Grazing Effects on Alfalfa Weevils, Weeds, and Forage Yields in Established Alfalfa
Authors: Chad Cummings D. , Berberet Richard C. , Stritzke Jim F. , Caddel John L.
Published: July 2010

Alfalfa (Medicago sativa L.) hay production for dairy and equine industries is a profitable enterprise in the Great Plains. However, as stands thin, forage production decreases and weeds increase, resulting in decreased returns. The objective of this research was to determine if alternative management strategies using October sod seeding plus March grazing could be utilized to increase forage production and control pests. Experiments were conducted at four locations in central Oklahoma from 1998–2000. Two ungrazed treatments (with and without pesticides) were compared with three treatments without pesticides but grazed by cattle in March. The three grazing treatments included: no sod seed, ryegrass (Lolium multiflorum Lam.) sod‐seeded in October, and wheat (Triticum aestivum L.) sod‐seeded in October. Grazing by cattle reduced alfalfa weevil (Hypera postica Gyllenhal) larval populations as effectively as insecticide application. In thin stands (<200 stems m−2), total forage yields were increased with alfalfa–grass mixtures by an average of 2.7 kg ha−1. However, alfalfa yields were decreased 0.9 kg ha−1 with sod‐seeded ryegrass (P = 0.05). In thin stands, sod‐seeded grass treatments were more effective at weed suppression than a herbicide treatment. Net returns from cool‐season forage production increased with sod seeding plus March grazing compared with net returns using conventional haying methods. In thin stands (<200 stems m−2), sod seeding of ryegrass or wheat plus March grazing provided greater net returns ($175 ha−1) than conventional practice of using pesticides and haying. In full stands (>250 stems m−2), net returns from conventional alfalfa management (using pesticides and only haying) were comparable to October sod seed plus March grazing treatments.
Soil Nitrate Concentrations Used to Predict Nitrogen Sufficiency in Relation to Yield in Perennial Grasslands
Authors: Collins Sister Augusta , Allinson Derek W.
Published: July 2010

A method of evaluating soil N present in a perennial grassland system could help determine the need for additional N and enable more accurate N fertilization recommendations. The purpose of this study was to establish a relationship between a critical level (CL) of soil nitrate N under perennial grassland and optimum yield in a three‐harvest system. A range of fertilizer treatments from 0 to 613 kg ha−1was applied across two growing seasons to mixed stands of perennial forage grasses at two sites in Connecticut. Soil samples were taken on a weekly basis, and soil ammonium N and nitrate N were measured. Nitrate N was correlated with relative yield for three harvests within each growing season, and CLs of nitrate were generated using Cate–Nelson, linear response plateau, and quadratic response plateau models. Ranges of critical nitrate levels during the first 2 wk of each cycle were established: 2.0 to 4.5 mg kg−1for the first harvest, 4.0 to 9.8 mg kg−1for the second harvest, and 2.0 to 11.0 mg kg−1for the third harvest. These values could be used to evaluate the necessity of adding N to a perennial grassland system in a three‐harvest rotation and aid in a more correct fertilization of perennial grasses by offering soil‐specific N evaluations.
Response of Soybean Yield Components to Management System and Planting Date
Authors: Pedersen Palle , Lauer Joseph G.
Published: July 2010

Soybean [Glycine max (L.) Merr.] area has increased tremendously in the upper Midwest over the last decade, but little information exists regarding the impact of management systems on soybean yield components. Our objective was to assess the effect of management system and planting date on soybean seed yield components and their development for environments typical of the upper Midwest. A field study was conducted from 1997 to 2000 using five management systems. Two newer released cultivars (CX232 and Spansoy 250) and one older cultivar (Hardin) were planted at two planting dates. Few interactions were observed in this study. Management system influenced development of the different yield components and produced seed mass ranging from 10.5 to 16.5 g 100 seed−1, seed number from 2878 to 3824 seeds m−2, pod number from 1182 to 1571 pods m−2, and seeds per pod from 2.36 to 2.49 seeds pod−1. Harvest index ranged from 56.2 to 58.0% across management systems. Hardin produced the highest harvest index (60.1%) and Spansoy 250 the lowest harvest index (54.5%). Tillage system affected yield components, with no‐tillage systems having 15, 9, and 9% greater seed mass, seed number per square meter, and pod number per square meter than the conventional tillage system, respectively. Early planting date produced higher seed number, pod number, and harvest index but lower seed number per pod than the late planting date. In conclusion, differences in yield components and their development emphasize the complexity of plant compensation in response to management system and tillage system.
Factors Underlying Yield Variability in Two California Rice Fields
Authors: Roel Alvaro , Plant Richard E.
Published: July 2010

Modern technologies associated with precision agriculture provide the opportunity to more precisely measure yield variability and the ecological processes underlying this variability. Effective analysis of data from these measurements requires statistical methods different from those traditionally employed on data from controlled agronomic experiments. Our objective was to develop and test multivariate statistical methods appropriate for use in analyzing precision agriculture data. We analyzed a data set taken from two commercial California rice fields and consisting of yield spatial trends together with soil core data from a grid of sample points. We used cluster analysis to discern spatiotemporal patterns in grain yield. We applied a Monte Carlo randomization process to the generation of clusters to analyze cluster stability. We then used classification and regression trees (CART) to determine the factors underlying cluster distribution. The clustering procedure successfully identified stable, physically meaningful clusters with recognizable spatial and temporal structure. Thus, the randomization procedure may present an attractive alternative to fuzzy clustering. The CART analysis identified some but not all of the factors underlying the cluster patterns. The number of available data values may have been too small to take advantage of the CART partitioning capabilities.
Economic Feasibility of Variable‐Rate Nitrogen Application Utilizing Site‐Specific Management Zones
Authors: Koch B. , Khosla R. , Frasier W. M. , Westfall D. G. , Inman D.
Published: July 2010

Variable‐rate technology (VRT) has been developed to variably apply crop inputs to manage in‐field variability. Although growers have begun to adopt VRT, its profitability is uncertain in N management. The objective of this study was to assess the economics of uniform vs. variable‐rate N fertilizer application under two N application scenarios (farmer vs. custom applications). On‐farm studies were conducted on two continuous corn (Zea maysL.) fields in northeastern Colorado under furrow and center‐pivot irrigation during the 2000 and 2001 growing seasons. The N management strategies were uniform, grid‐based, site‐specific management zone–constant yield goal (SSMZ‐CYG) and site‐specific management zone–variable yield goal (SSMZ‐VYG). “Profit and loss” software was used to analyze the economics of each N management strategy and determine which N strategy was most profitable. Results from three site‐years consistently indicated that less total N fertilizer (6–46%) was used with the SSMZ‐VYG N management strategy when compared with uniform N management. Net returns from the SSMZ‐VYG N management strategy were $18.21 to $29.57 ha−1more than uniform N management. Results of this study suggest variable‐rate N application utilizing site‐specific management zones are more economically feasible than conventional uniform N application.
Hedgerow Pruning Management Effects on Maize Yield and Nitrogen Uptake in an Alley Cropping System in Haiti
Authors: Isaac Lionel , Shannon Dennis A. , Wood C. Wesley
Published: July 2010

Hedgerow management is crucial to successful alley cropping. Leucaena [Leucaena leucocephala (Lam.) de Wit] hedgerow management practices were assessed over four seasons for effect on maize (Zea mays L.) yield and N recovery in alley cropping. Maize was planted between leucaena hedgerows spaced 4 m apart on a Lithic Eutropepts. Pruning application and regime factors were arranged in 3 × 3 factorial augmented with a control (stone walls) in randomized complete block design with three replicates. Hedgerows were pruned at 0.50 m height at (a) maize planting and at 30 d after planting (DAP), (b) planting and 40 DAP, or (c) planting, 30 and 60 DAP. Prunings were (a) removed from plots, (b) applied as mulch or (c) incorporated into the soil at planting. A hedgerow + fertilizer treatment in an adjacent trial was included for comparison. Soil application of leucaena prunings increased average maize yield and grain N uptake by 157 and 163%, respectively, compared to when prunings were removed. Addition of inorganic fertilizer further increased maize yield and N recovery. Pruning three times per season gave higher maize yield, N uptake and N recovery than pruning twice, but reduced leucaena biomass and N yield. Pruning twice per season, with the second pruning at 40 rather than at 30 DAP, increased biomass N yield but reduced N recovery over the seasons. Alley cropping with soil application of three prunings per season averaged 31% higher maize yield and 48% higher N uptake than control. N recovery was enhanced by soil application of three prunings per crop and by fertilization.
Tillage and Poultry Litter Application Effects on Cotton Growth and Yield
Authors: Reddy Chandra K. , Nyakatawa E. Z. , Reeves D. W.
Published: July 2010

Although use of no‐tillage in cotton (Gossypium hirsutumL.) production in the southeast USA has dramatically increased recently, reports of reduced seedling emergence, poor plant establishment, reduced growth, delayed maturity, and low yields still constrain adoption. The objective of this study was to evaluate the effect of tillage systems on growth and yield of cotton grown in rotation with a winter rye (Secale cerealeL.) cover crop with poultry litter and ammonium nitrate fertilizer application in north Alabama. Results from 1996 to 2001 are reported in this paper. Treatment factors were three tillage systems, two cropping systems, two N sources, and four N levels. Winter rye cover cropping increased surface residue cover by up to 35, 70, and 100% in conventional tillage, mulch tillage, and no‐tillage systems, respectively. Despite initial differences in rate of seedling emergence, final seedling establishment averaged 10 seedlings m−1in all treatments. At the rate of 100 kg N ha−1, the effect of poultry litter on cotton growth and yield parameters was generally lower or similar to that of ammonium nitrate at the rate of 100 kg N ha−1. However, at 200 kg N ha−1, poultry litter improved cotton growth and lint yield compared with ammonium nitrate at 100 kg N ha−1or poultry litter at 100 kg N ha−1. Cotton lint yields averaged over all treatments ranged from 1128 to 1405 kg ha−1over the study period. With adequate N fertility from poultry litter, no‐tillage and mulch‐tillage systems with winter rye cover cropping are ideal for cotton production in the southeast USA.