bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting Straw Yield of Hard Red Spring Wheat
Authors: Engel R. E. , Long D. S. , Carlson G. R.
Published: July 2010

Accurate estimates of straw production for spring wheat (Triticum aestivum L.) are important in the Great Plains for conservation planning, nutrient cycling, and fertilizer recommendations. Frequently, these estimates are based on grain yield and the assumption of a constant ratio between straw and grain. This approach may not always be accurate because straw/grain ratios can vary greatly across environments and genotypes. Spring wheat studies were conducted to contrast straw/grain ratios over diverse water and N environments and to determine if plant height and grain protein at maturity, in addition to grain yield, would significantly improve predictions of straw production. A 3‐yr field study consisting of four cultivars, three water regimes, and a wide range of N levels served as a database for this analysis. Straw/grain ratios ranged from 0.91 to 2.37 and were affected by water, N, and cultivar selection. Extended periods of water stress during grain fill and/or vegetative growth and improved N fertility generally resulted in wider ratios. Stability of straw/grain ratios over the diverse environments improved as cultivar height decreased. Straw yield models that considered only grain yield provided a modest fit to the data (R2 = 0.66, SE = 701 kg ha−1). Prediction models that included terms for plant height and plant N status (straw N or grain protein) in addition to grain yield provided a considerably better fit to the experimental data (R2 = 0.88, SE = 425). Observations from validation data sets confirmed that inclusion of plant height (two of two data sets) and grain protein (one of two data sets) improved accuracy of straw yield predictions.
Grazing‐Tolerant Alfalfa Cultivars Perform Well under Rotational Stocking and Hay Management
Authors: Bouton J. H. , Gates R. N.
Published: July 2010

Grazing‐tolerant alfalfa (Medicago sativa L.) cultivars are developed using continuous stocking with beef cattle (Bos taurus) during screening and selection. Alfalfa is mainly recommended for use in hay making and under rotational stocking rather than continuous stocking. Performance of alfalfa cultivars selected under the specificity of intensive, continuous stocking in recommended management systems is unknown. This study was conducted to test survival and performance of alfalfa populations selected with continuous stocking against their parental cultivar germplasms (‘Apollo’, ‘Diamond’, ‘5432’, and ‘Florida 77’) at two Georgia locations (Eatonton and Tifton) under the following management conditions: grazing to close stubble heights (5–7 cm) with continuous stocking, grazing to close stubble heights (5–7 cm) with rotational stocking (7 d grazing and 28 d rest), and standard hay harvesting. At Eatonton, plant survival was similar (52–53%) for the rotational stocking and hay harvest treatments, with all entries in these treatments exhibiting better survival than in the continuously stocked treatment (38%). At Tifton, stand survival improved as management changed from continuous stocking (24%) to rotational stocking (46%) to hay harvest management (63%). At both test locations, grazing‐tolerant entries demonstrated higher plant survival rates than parental populations when averaged across all management treatments. Dry matter yields of the grazing‐tolerant entries were no different, or were higher during 1 yr at Tifton, than their parental populations. It is therefore a good strategy for producers practicing continuous stocking, rotational stocking, or hay making to use grazing‐tolerant cultivars rather than cultivars not selected for grazing tolerance.
Sheath Blight Severity and Rice Yield as Affected by Nitrogen Fertilizer Rate, Application Method, and Fungicide
Authors: Slaton Nathan A. , Cartwright Richard D. , Meng Jie , Gbur Edward E. , Norman Richard J.
Published: July 2010

Sheath blight, Rhizoctonia solani (Kuhn), is the most economically important disease in the Midsouth rice (Oryza sativa L.)‐producing area of the USA. The use of excessive N fertilizer has been observed to increase sheath blight damage to rice, but the effect of specific N application rates and timing on sheath blight damage and the resulting rice grain yield are unknown. The primary objective of this study was to examine the effect of N application rate and time on rice grain yield and development of sheath blight. A 3‐yr study contained 20 treatments with all possible combinations of two N fertilization methods (single preflood and two‐way split), five N fertilizer rates (0–250 kg N ha−1), and two rates of azoxystrobin {methyl (E)‐2‐[2‐[6‐(2‐cyanophenoxy)pyrimidin‐4‐yloxy]phenyl]‐3‐methoxyacrylate} fungicide (0 and 0.22 kg ha−1). Application of azoxystrobin, averaged across all other treatment factors, produced a mean rice grain yield of 8740 kg ha−1, which was 16% greater than treatments not receiving azoxystrobin fungicide. Relative lesion height (RLH), averaged across N fertilizer treatments, increased with time when no fungicide was applied. Early‐season application of fungicide prevented disease development from 4 to 6 wk. Fungicide application suppressed RLH but did not alter the N rates required to produce maximum grain yields. Application of high preflood N fertilizer rates, regardless of method, increased the initial RLH during early reproductive growth but had little effect on the RLH after heading. The effect of RLH on grain yield showed similar patterns as that found for total N rate on grain yield. The N rates required to produce maximum yields also tend to enhance early‐season sheath blight.
Evapotranspiration from Northern Semiarid Grasslands
Authors: Frank A. B.
Published: July 2010

Management of forage production for livestock grazing on semiarid grasslands depends on water availability. Evapotranspiration (ET) was measured using the Bowen ratio energy balance method on three grasslands at Mandan, ND: a nongrazed mixed‐grass prairie (prairie), a grazed mixed‐grass prairie (grazed prairie), and a grazed western wheatgrass [Pascopyrum smithii (Rybd) Löve] site (western wheatgrass). Measurements were made from 24 April to 17 October (the growing period) in 1996, 1997, and 1998. Peak ET rates generally coincided with periods of peak biomass production and occurred between early July and early August. Peak biomass averaged 1097 kg ha−1 for the prairie, 1227 kg ha−1 for grazed prairie, and 1725 kg ha−1 for western wheatgrass, and peak leaf area index averaged 0.38 for the prairie, 0.44 for grazed prairie, and 0.59 for western wheatgrass. Growing period (175 d) ET averaged 489 mm for the prairie, 455 mm for the grazed prairie, and 497 mm for the western wheatgrass while growing period precipitation averaged 320 mm. Evapotranspiration of grazed prairie was 7% less than nongrazed prairie and 8% less than western wheatgrass. Evapotranspiration of the nongrazed prairie and the grazed western wheatgrass were similar. The ratio of the latent heat of ET to net radiation averaged 0.25 for grazed prairie and 0.28 for prairie, suggesting that grazing changed the canopy structure and energy budget components that affected ET. These results suggest that in a semiarid environment, proper grazing of prairie grasslands conserves soil water.
Timing of Nitrogen Fertilization in Wheat under Conventional and No‐Tillage System
Authors: Melaj Mariana A. , Echeverría Hernán E. , López Silvia C. , Studdert Guillermo , Andrade Fernando , Bárbaro Néstor O.
Published: July 2010

Grain yield, N accumulation, and remobilization in wheat (Triticum aestivumL.) may be modified by fertilization timing, tillage system, and environmental conditions. Little information about the combination of tillage effect and fertilization timing on wheat development is available in the southeastern Humid Pampa Region. The objective of this work was to study the timing of fertilization effect under two tillage systems on wheat grain yield and N accumulation and losses. Two field experiments were performed during 1998 and 1999, at Balcarce, Argentina, under no‐tillage (NT) and conventional tillage (CT). Nitrogen was applied as15N‐labeled urea at two rates (0 and 120 kg N ha−1) and at two times (sowing and tillering). Tillage system affected grain yield only in 1998 when NT promoted better soil water availability conditions. Highest yields were obtained when urea was applied at tillering. Nitrogen in plant derived from fertilizer (Ndff) at physiological maturity ranged from 21.9 to 70.4 kg ha−1in the whole plant. Late fertilization increased Ndff recovery in whole plant and in grain. This effect was more pronounced in NT than in CT. No effect of tillage was found along growing season. No dry matter or net total N losses were detected during grain filling both years, but N accumulation in fertilized plants virtually ceased by ear emergence in 1999. A significant N fertilizer loss occurred during grain filling in 1999 (7.8–10.9 kg ha−1Ndff). Nitrogen losses were related to low grain yield, high amount of stored N at ear emergence, and environmental conditions during grain filling.
Drought Avoidance Assessment for Summer Annual Crops Using Long‐Term Weather Data
Authors: Purcell Larry C. , Sinclair Thomas R. , McNew Ronald W.
Published: July 2010

Seasonal rainfall is a key factor determining yield of nonirrigated, summer crops. In temperate regions, however, systematic analyses of long‐term weather data have not been used for directing breeding programs or for crop management options. We evaluated long‐term weather data (36–98 yr) for 16 sites in four geographical regions in the USA to assess the potential for drought avoidance. For each day of year when the probability (P) of having a minimum temperature <0°C was less than 0.05, water deficit was estimated as the difference between the 7‐d running sums of rainfall and potential evaporation. For comparative purposes across locations, a 7‐d water deficit >50 mm was defined as a drought. For the Midsouth, there were approximately 62 d at both the beginning and end of the growing season with P ≤ 0.20 of drought. In the Southeast, there were approximately 48 d and 121 d at the beginning and end of the growing season, respectively, with P ≤ 0.20 of drought. For the Midwest, P of drought was ≤0.20 throughout the growing season for three of the four sites, and it was concluded that a 50‐mm water deficit was not likely to be a production constraint on the deep soils of the Midwest. For the Northern Great Plains, P of drought was >0.20 for more than half of the region's growing season. This meteorological approach for assessing drought may provide insights for drought avoidance in breeding and crop management.
High Temperatures during the Grain‐Filling Period Do Not Reduce the Potential Grain Dry Matter Increase of Rice
Authors: Kobata Tohru , Uemuki Naoya
Published: July 2010

High temperatures during the grain‐filling period (GFP) of rice (Oryza sativa L.) increase the grain dry matter increase rate (GIR), but this increase in GIR is insufficient to completely compensate for the concomitant reduced GFP, and as a result, grain yield decreases. The shortfall in GIR as temperatures increase has been believed to signify a reduction of the potential GIR as a sink capacity. However, we suspect that lack of assimilate supply to the grain, rather than the decreased potential GIR, lowers the GIR and causes reduced grain weight. Our objective was to determine if the grain weight could reach full potential under higher temperature conditions if assimilate supply during the GFP was sufficient to sustain the increased GIR. Rice was grown at three locations in western Japan over 3 yr. At one location, plots were covered with plastic film during the GFP to increase temperature. Spikelet filling percentages (F%) at maturity varied between 70 and 90% when mean temperatures ranged between 23 and 29°C during the GFP. When plots were thinned to half density during GFP, all F% were approximated by a single logistic equation based on accumulated temperature, with a ceiling of 90%. Hence, thinning can overcome the lower F%. These results suggest that potential GIR in rice is not reduced by high temperatures during the GFP. Yield reductions commonly associated with such conditions are likely due to the failure of assimilate supply to the grain to meet the requirements of the accelerated GIR.
Modeling Nitrogen Management Effects on Winter Wheat Production Using RZWQM and CERES‐Wheat
Authors: Saseendran S. A. , Nielsen D. C. , Ma L. , Ahuja L. R. , Halvorson A. D.
Published: July 2010

Agricultural system models can provide an alternative, less time‐consuming and inexpensive means of determining the optimum crop N requirement under varied soil and climatic conditions. In this context, we parameterized the Root Zone Water Quality Model (RZWQM) for winter wheat (Triticum aestivum L.) production and then evaluated it along with the CERES‐Wheat model to assess their potential as N management tools at Akron, Co. Both models were evaluated with data from five N treatments (0, 28, 56, 84, and 112 kg N ha−1) and three crop seasons (1987–1988, 1988–1989, and 1989–1990). Data from 1987–1988 zero‐N treatment were used for model calibration, and the rest of the data were used for model validation. Genetic coefficients for winter wheat (cv. TAM 107) were developed for the CERES‐Wheat model. The crop parameters required for the generic crop model of RZWQM were parameterized using information from the literature or by calibration. Both models were calibrated first for soil moisture and then for biomass and grain yield. Grain yield predictions had a root mean square error (RMSE) of 500 and 363 kg ha−1, respectively, for CERES‐Wheat and RZWQM. Aboveground biomass was predicted with RMSEs of 1247 and 1441 kg ha−1, respectively. Long‐term simulations of both RZWQM and CERES for winter wheat growth using historical weather data (1912–2001) showed that 56 kg ha−1 N applied as broadcast incorporated is a viable N management option in eastern Colorado, taking into account the grain yield, crop N uptake, N leaching into groundwater, and residual soil N at harvest. Model simulations also showed that the wheat–fallow cropping system is less water use efficient than a continuous wheat system under rainfed agriculture in eastern Colorado.
Maturity and Leaf Shape as Traits Influencing Cotton Cultivar Adaptation to Dryland Conditions
Authors: Stiller Warwick N. , Reid Peter E. , Constable Gregory A.
Published: July 2010

Worldwide, unreliable rainfall is the primary limitation to dryland cotton (Gossypium hirsutum L.) yields. Adaptation to these water stress environments has been and still is an important component of many crop improvement programs. This paper summarizes the results of cultivar experiments across three sites and six seasons comparing irrigated and dryland environments in Australia, with the objective of determining the extent of irrigation × cultivar interactions for yield and fiber quality, the effect maturity and leaf type have on those interactions, and the implications this has for a breeding program. On average, dryland cotton yielded 48% of irrigated cotton, and fiber lengths were 4% shorter. There was a significant irrigation × cultivar interaction, with two okra leaf cultivars yielding relatively more under dryland conditions. This interaction varied with site, suggesting that the number of dryland sites utilized in the breeding program could be increased, and consistency of cultivar rankings each season indicated the number of testing seasons could be decreased. It was also concluded that selection under dryland conditions would be beneficial. The data from these experiments indicated a yield penalty for early maturing cultivars under dryland conditions in these environments. There was a strong positive association between maturity and lint yield, with an increase of 34.4 kg lint ha−1 for every day delay in maturity. Agronomic water use efficiency (WUE) varied among cultivars, with a full‐season okra leaf cultivar, Siokra L23, having the highest WUE (2.87 kg lint ha−1 mm−1 evapotranspiration) and the highest yield.
Relationship of Corn and Soybean Yield to Soil and Terrain Properties
Authors: Kaspar T. C. , Pulido D. J. , Fenton T. E. , Colvin T. S. , Karlen D. L. , Jaynes D. B. , Meek D. W.
Published: July 2010

Farmers will be better able to implement site‐specific management practices when they understand the causes of spatial and temporal variability of corn (Zea maysL.) and soybean [Glycine max(L.) Merr.] yield in their fields. Our objectives were to determine if a data set containing 20 soil and terrain variables could explain spatial yield variability better than a subset of seven more easily measured variables and to determine whether the relative importance of factors in explaining yield variability differed between corn and soybean or between wet and dry years. Yield data were collected for 11 yr in a 16‐ha field in central Iowa. Soil and terrain variables measured included: A horizon depth, carbonate depth, pH, coarse sand, sand, silt, clay, organic C, N, Fe, K, P, and Zn; and seven easily measured variables: electrical conductivity, soil color, elevation, slope, profile curvature, plan curvature, and depression depth. Factor analysis of the variables followed by regression of yield on the resulting factors showed that the 20‐variable set explained more of the spatial variation in yield than the subset of seven variables. Further, the analysis of the 20‐variable data set showed that soybean yield was affected more by pH, more by closed depressions in wet years, and less by curvature in dry years than corn yield. Similarly, yield was negatively affected by closed depressions and lower landscape positions in wet years, whereas these factors had either no effect or a positive effect in dry years. Alternately, curvature had a negative effect in dry years and no effect in wet years.
Corn Response to Starter Fertilizer and Tillage across and within Fields Having No‐Till Management Histories
Authors: Bermudez Manuel , Mallarino Antonio P.
Published: July 2010

Corn (Zea mays L.) early growth often is slower in no‐tilled than tilled soils. Starter fertilization usually increases early plant growth but has inconsistent effects on grain yield. This study assessed (i) starter and tillage effects on corn grain yield, dry weight (DW), and N, P, and K uptake at the V5–V6 stage and (ii) the within‐field variation of responses. Seven replicated strip trials were conducted on fields previously managed with no‐tillage using yield monitors and global positioning systems (GPS). Treatments were no‐starter and liquid starter with or without tillage and were applied in addition to farmers’ normal broadcast NPK rates. Starter applied 3.9 to 27.2 kg N ha−1, 5.2 to 24.2 kg P ha−1, and 0 to 4.1 kg K ha−1 across fields. The tillage treatment was spring disking or strip tillage. Tillage increased (P ≤ 0.05) yield in four fields (210–500 kg ha−1), starter increased yield in three fields (93–522 kg ha−1), and both treatments usually increased DW and nutrient uptake. There were no treatment interactions. Tillage and starter fertilization did not influence yield variability but increased DW and nutrient uptake variability. Soil test results (P, K, pH, and organic matter) or soil series could not always identify fields where starter would increase yield. However, in two fields, starter increased yield only in areas with Bray‐1 soil P < 16 mg P kg−1. On average, tillage increased yield 2.5%, starter increased yield 1.1%, and DW or nutrient uptake responses to either treatment were 20 to 30%. Large DW and nutrient uptake responses to starter did not translate into large or frequent yield responses.
Periodic Flooding and Water Table Effects on Two Sugarcane Genotypes
Authors: Glaz Barry , Morris Dolen R. , Daroub Samira H.
Published: July 2010

Sugarcane (Saccharum spp.) in Florida is increasingly exposed to periodic floods and high water tables for extended durations. We evaluated the effects of periodic flooding, followed by drainage, on morphological characteristics and cane and sugar yields of two sugarcane genotypes. From 2000–2002, experiments were conducted in lysimeters filled with Pahokee muck soil. Flooding was imposed for 7 d during five, nine, and nine 21‐d cycles in 2000, 2001, and 2002, respectively. Cycles commenced when sugarcane leaves covered the rows and were discontinued in mid‐October. Water table depths during the 14‐d drainage period of each cycle were 16, 33, or 50 cm. A fourth treatment was maintained continuously at a 50‐cm water table depth. Genotype CP 95‐1429 yields were not affected by water table or flooding. For CP 95‐1376 in periodic‐flooding treatments, lowering the water table in 1‐cm increments increased cane and sugar yields by 0.16 and 0.02 kg m−2, respectively, in 2000 and 0.25 and 0.03 kg m−2, respectively, in 2001. Water table depth during drainage did not affect CP 95‐1376 yields in 2002, perhaps because of a longer duration between planting and initial flooding in 2002. Each day of flooding reduced cane and sugar yields of CP 95‐1376 by 0.17 and 0.02 kg m−2, respectively, in 2000 and by 0.21 and 0.03 kg m−2, respectively, in 2002. Flooding might not have reduced yields of CP 95‐1429 because of its ability to form aerenchyma in the stalks before exposure to flooding. Such genotypes should be able to tolerate flooding for at least 1 wk.
Effects of Chloride Fertilization on Wheat (Triticum aestivum L.) Productivity in the Sandy Pampas Region, Argentina
Authors: Díaz‐Zorita M. , Duarte G. A. , Barraco M.
Published: July 2010

The soils from the sandy Pampas region (Argentina) are coarse‐textured Mollisols with high to very high extractable K levels. However, in several KCl fertilization field trials, wheat (Triticum aestivum L.) grain yield and alfalfa (Medicago sativa L.) dry matter production increments have been reported. Our objective was to determine the contribution of Cl− fertilization on dryland spring wheat productivity. The study was performed during the 2001 and the 2002 growing seasons on 10 experimental sites establishing 14 treatments in completely randomized blocks with four replications: Cl− fertilization rates (0, 23, 46, and 69 kg ha−1), Cl− fertilizer sources (KCl and NH4Cl), and crop disease control (with and without fungicide applications during stem elongation). Chloride fertilization increased grain yields in 50% of the sites independently of the fertilizer source and the fungicide treatments. Averaged over the 10 locations, the grain yield response to Cl− fertilization was of 253 kg ha−1, and it was mostly explained by a greater number of grains per square meter. Soil Cl− levels >13.2 mg kg−1 (0.0 to 0.2 m) were adequate for maximum grain yields. Foliar fungicide application also improved wheat grain production, enlarging the single weight of the grains. In the absence of water, N, P, and S deficiencies, the fertilization with 23 to 46 kg ha−1 of Cl−–containing fertilizers after the emergence of wheat crops is a recommended practice for achieving high‐yielding crops in the sandy Pampas region of Argentina.
Symbiotic Dinitrogen Fixation in Forage Legumes Amended with High Rates of De‐Inking Paper Sludge
Authors: Allahdadi Iraj , Beauchamp Chantal J. , Chalifour François‐P.
Published: July 2010

The paper de‐inking process produces a waste by‐product, de‐inking paper sludge (DPS), which contains paper fibers, clay particles, and inks and has high C and Ca and low N and P concentrations. Use of high rates of DPS to increase the soil organic matter thus requires provision of high rates of N for adequate plant growth. Using dinitrogen (N2)‐fixing forage legumes is an alternative to the N fertilization under such circumstances. In a 2‐yr field study (1995 and 1996), the effect of different rates of DPS (0, 50, or 100 Mg dry matter ha−1), applied once in October 1994, were evaluated on symbiotic N2 fixation of forage legumes established on two soil types in Eastern Quebec, Canada. Symbiotic N2 fixation was measured in alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), red clover (Trifolium pratense L.), and sweetclover (Melilotus officinalis L.); bromegrass (Bromus inermis L.) was used as the reference (non N2–fixing) crop. Dinitrogen fixation was estimated by the 15N natural abundance method. The percentages of N derived from the atmosphere increased significantly with DPS in the year of establishment (1995). In the first production year (1996), the effects of DPS on N2 fixation were mainly observed at the first cut. Our results show that DPS used as an organic amendment generally led to similar or greater forage legume productivity and greater N2 fixation compared with unamended controls in the first production year and is compatible with sustainable agricultural practices.
Canopy Resistance as Affected by Soil and Meteorological Factors in Potato
Authors: Amer Kamal H. , Hatfield Jerry L.
Published: July 2010

Precision irrigation requires a method of quantifying the crop water status or root zone depletion of water to determine when and how much water to apply to the soil. Changes in canopy resistance (rc) and canopy temperatures have the potential of being used as a crop water status indicator for irrigation management. A study was conducted on potato (Solanum tuberosum L.) grown in northern Egypt at Shibin El‐Kom on an alluvial loamy soil for winter (20 Sept. 2001 through 20 Jan. 2002) and spring (1 Feb. 2002 through 20 May 2002) seasons to determine if rc derived from energy balance and plant parameters could be used to determine the onset of water stress and the amount of water required to refill the soil profile. Diurnal rc was determined for well‐watered conditions and achieved minimum values of 20 and 10 s m−1 at noontime during winter and spring periods, respectively. A power relationship of −0.86 for well‐watered conditions was developed between rc and net radiation (Rn) at various plant growth stages. In deficit soil water conditions, rc increased linearly with decreasing available soil water (ASW), with a change in potato rc of 0.75 and 0.39 s m−1 per percentage ASW for 1 and 2 MJ m−2 h−1 of Rn at midgrowth, respectively. A ratio of actual/potential canopy resistance (rc/rcp) was derived to normalize the meteorological differences between growing seasons. This ratio was 2.5 when 50% of ASW was removed and can be used as a parameter to determine the need for irrigations using weather factors and canopy temperature. Canopy resistance increased linearly with increasing soil solution salinity, electrical conductivity, when the soil solution was above the threshold soil salinity value. A ratio of rc/rcp was found to normalize the effects of different environments across saline and water deficit conditions.
Land Application of Oily Food Waste and Corn Production on Amended Soils
Authors: Rashid M. T. , Voroney R. P.
Published: July 2010

Oily food waste containing high concentrations of fat, oil, and grease (FOG) is produced by the food service and food production/processing industries. Fat, oil, and grease have a high C/N ratio (90:1) and, if applied to agricultural soils, may affect the availability of N to crops, due to soil N immobilization during its decomposition. Several field experiments were conducted on silt loam and loam soils (fine‐loamy mixed, mesic Glossoboric Hapludalfs) from 1995–1997 to determine: (i) effect of FOG on corn (Zea maysL.) crop yields, (ii) N requirements of corn grown on FOG‐amended soils, (iii) contribution to soil C, and (iv) its accumulation in soil after continuous application. Corn grain yields were maintained with FOG applied at 5, 10, and 15 Mg ha−1, providing that sufficient N was available to fulfill the needs of soil microorganisms during FOG decomposition and crop growth. The N rates ranged from 170 to 510 kg N ha−1for these FOG application rates. Soil organic C was significantly increased by 9 and 19% with the continuous FOG application for 3 yr at 10 and 15 Mg FOG ha−1yr−1. The residual FOG contents after 3 yr at these application rates were <2% of the total FOG applied with no expected FOG buildup in soil. Corn grain yields were not affected by FOG application in fall and were equal to control plots during 1996 and 1997. However, corn grain yields were decreased by FOG applied in spring, and supplemental N (62 and 59 kg N ha−1in 1996 and 1997, respectively) was required to maintain yields similar to control plots.
Living Mulches of Legumes in Imidazolinone‐Resistant Corn
Authors: Duiker Sjoerd W. , Hartwig Nathan L.
Published: July 2010

Living mulches of legumes are permanent cover crops that can fix atmospheric N and improve soil quality. The objectives of this study were to determine effects of living mulches on corn (Zea mays L.) yield and N fertilizer response and on soil quality. In this split‐plot design, living mulches were main plots and N rates (0–225 kg ha−1 N) subplots. Living mulches were crownvetch (Coronilla varia L.) cultivars Penngift and Pennmulch, flatpea (Lathyrus sylvestris L.) cultivar Lathco, birdsfoot trefoil (Lotus corniculatus L.) cultivars Empire and Steadfast, hairy vetch (Vicia villosa Roth), and galega (Galega officinalis L.). The crop was rainfed imidazolinone (IMI)‐resistant corn on a Murrill silt loam (Typic Hapludult) in central Pennsylvania. Only crownvetch, flatpea, and birdsfoot trefoil (BFT) cultivars survived the herbicide program. Living mulches did not reduce corn yields, except in the dry year of 1995. The average N fertilizer equivalency of Penngift, Pennmulch, Empire, Steadfast, and Lathco was 71, 45, 44, 13, and 50 kg ha−1 yr−1, respectively, at 0 N rates. Their N fertilizer equivalency decreased to zero, however, with increasing N fertilizer rates. Bulk density, soil organic C content, and infiltration rate were not significantly improved after 10 yr of Penngift living mulch. When suppressed severely, crownvetch, BFT, and flatpea can be managed without yield reduction to IMI‐resistant corn, but then N contribution to corn and soil quality benefits will be limited. For maximum corn yield, full N rates are required with these living mulches.
Long‐Term Fertilization Effects on Crop Yield and Nitrate Nitrogen Accumulation in Soil in Northwestern China
Authors: Yang Shengmao , Li Fengmin , Malhi Sukhdev S. , Wang Ping , Suo Dongrang , Wang Jianguo
Published: July 2010

A long‐term (1982 to 2000) field experiment was conducted at Zhangye, Gansu, China, on a sandy clay loam (Typic Anthrosol) under wheat (Triticum aestivum L.)–wheat–corn (Zea mays L.) rotation to determine the effects of N, P, and K chemical fertilizers and farmyard manure (M) on grain and straw yield, harvest index (HI), protein concentration, and N uptake in grain and straw and accumulation of nitrate N (NO3–N) in the soil profile (0–180 cm). The eight treatments from various combinations of fertilizers and M were check, N, NP, NPK, M, MN, MNP, and MNPK. Mean grain yield decreased in the order of MNPK ≥ MNP > NPK > MN > NP > M > N > check (i.e., 8.01, 8.00, 7.51, 7.28, 7.00, 5.50, 4.89, and 3.43 Mg ha−1, respectively). Yield response to applied N and P increased with time since yields in the check plots declined with time. Potassium fertilizer application provided no, slight, and dramatic increase in grain yield during the initial 6 yr, next 5 yr, and last 8 yr, respectively. Response of straw yield to fertilizers and M was similar to the grain yield. Mean HI increased with fertilizers in no‐M treatments for both crops. Crude protein concentration and N uptake in grain and straw increased markedly with fertilizers, and M increased it further. Fertilizers (N, NP, and NPK) led to NO3–N accumulation in most subsoil layers. Combined applications of fertilizers and M reduced soil NO3–N accumulation in soil compared with fertilizers alone. In conclusion, the findings suggest that it is important to use balanced application of chemical fertilizers and M at proper rates in order to protect soil and underground water from potential NO3–N pollution while also sustaining high crop production.
The Range of the Critical Nitrogen Dilution Curve for Maize (Zea mays L.) Can Be Extended Until Silage Maturity
Authors: Herrmann Antje , Taube Friedhelm
Published: July 2010

The concept of critical N concentration (Ncrit) assumes at any time a minimum shoot N concentration necessary for maximum biomass production. For maize (Zea mays L.), Ncrit has of now been confirmed only from emergence to silking plus 25 d. These results were based on mineral N fertilization. In the present study, we verified that the validity of the concept can be extended to silage maturity and that it is not only applicable to mineral but also to organic N fertilizer. Our investigation included a 3‐yr N fertilization experiment comprising four mineral N fertilization rates (0, 50, 100, and 150 kg N ha−1) and three slurry treatments (0, 20, and 40 m3 ha−1), respectively. A quadratic‐plateau model was used to determine Ncrit values. An analysis of covariance indicated that the Ncrit‐to‐biomass relationship was extendible to the postsilking stages. The Ncrit [g N kg−1 dry matter (DM)] was then successfully described by a mononomial function of biomass W (t DM ha−1): Ncrit = 34.12·W
−0.391 We suggest restricting the model to growth stages with biomass exceeding a threshold of 1 t ha−1 Model validation against an independent data set comprising different hybrids and soil conditions indicated a satisfactory separation of N‐limiting and non‐N‐limiting growth. The Ncrit concept thus seems to provide an efficient tool for assessing the N status of forage maize for mineral and organic N fertilizers and for a broad range of hybrids, climates, and soil conditions.
No‐Tillage Corn and Grain Sorghum Response to Cover Crop and Nitrogen Fertilization
Authors: Reinbott Timothy M. , Conley Shawn P. , Blevins Dale G.
Published: July 2010

No‐tillage cropping systems may benefit from the addition of winter annual cover crops through decreased soil erosion, accumulation of biologically fixed N, or increased crop yield. The objectives of this research were to assess the amount of cover provided by winter annual legumes and oat (Avena sativa L.) to quantify the fertilizer N equivalent value of each cover crop system and the effect of cover crop and N rate on corn (Zea mays L.) and grain sorghum [Sorghum bicolor (L.) Moench] grain yield. Two experiments, one in corn and one in sorghum, were conducted in 1997, 1998, and 1999. In each experiment, the main‐plot effect was cover crop treatment while the subplot effect was spring N rates of 0, 56, 112, and 168 kg ha−1. The addition of oat to the legume cover crop treatments increased fall ground cover but decreased total spring dry matter yield. Maximum spring dry matter yield was greatest in the hairy vetch (Vicia villosa Roth)‐alone treatment. Hairy vetch alone also produced the greatest mean fertilizer N equivalent value in the corn and sorghum experiments, 43.6 and 56.9 kg N ha−1, respectfully. These values, however, were variable among years. Corn and sorghum grain yield were greatest in the Austrian winter pea (Pisum sativum L.) and hairy vetch full seeding rate treatments, 5.19 and 7.06 Mg ha−1, respectfully. Our results indicate that winter annual cover crops provide several distinct benefits to no‐tillage corn and sorghum production systems and that cover crops should be selected based on specific grower needs.
Cropping Systems Research in the World's Driest Rainfed Wheat Region
Authors: Schillinger William F. , Young Douglas L.
Published: July 2010

Winter wheat (Triticum aestivum L.)–summer fallow (WW‐SF) is the predominant cropping system in the 120000‐ha Horse Heaven Hills (HHH) region in south‐central Washington, USA. Blowing dust from residue‐ and roughness‐deficient SF results in soil loss and causes health problems. Annual no‐till cropping to replace SF would provide year‐round protection against wind erosion. A 6‐yr field study was conducted from 1996 to 2002 to evaluate the agronomic and economic feasibility of continuous annual no‐till hard red spring wheat (HRSW) as an alternative to traditional WW‐SF. Long‐term average annual precipitation at the experiment site is 152 mm, which we believe is the lowest for any nonirrigated wheat region of the world. Annual precipitation during the study ranged from 111 to 240 mm and averaged 153 mm, with two wet years followed by a 4‐yr drought. Russian thistle (Salsola iberica Sennen and Pau) heavily infested HRSW plots and depleted soil water during the two wet years. Seed‐zone water content in SF was sufficient to plant WW in late August in only 2 of 6 yr. Mean (6‐yr) grain yield was 1190 kg ha−1 for WW‐SF (one crop every 2 yr) and 530 kg ha−1 for annual no‐till HRSW. The number of kernels per spike had a significant contribution to yield during years of acute water stress. Net economic returns for annual HRSW lagged WW‐SF by an average $95 ha−1 yr−1. Although continuous annual no‐till cropping has clear environmental advantages, it is not economically competitive with WW‐SF with current technology in the HHH.
Seeding Rate Influence on Yield and Yield Components of Irrigated Winter Wheat in a Mediterranean Climate
Authors: Lloveras Jaime , Manent Josep , Viudas Javier , López Antonio , Santiveri Paquita
Published: July 2010

It is difficult to establish agronomic practices for wheat (Triticum aestivum L.) production in Mediterranean regions because of high annual variability in rainfall. Plant density is a factor of particular importance in wheat production systems because it can be controlled. This study was conducted to determine the optimum seeding rates of Mediterranean types of wheat in irrigated Mediterranean systems. Field experiments were conducted under irrigation at two locations of the Ebro Valley, Spain, during two growing seasons, 1999–2000 and 2000–2001. Six seeding rates were compared: 150, 175, 250, 300, 400, and 500 seeds m−2 with four adapted wheat varieties including a hybrid wheat. Seeding rate affected grain yield and yield components in three of the four environments, but its effect varied with the environment. The plant densities giving the highest yields were at least 400 to 500 plants m−2 for most of the varieties studied. The results suggest that the rate of seeding under irrigation for Mediterranean areas might be higher than those used in other wheat‐growing areas.
Evaluation of Two Temperature Stress Indices to Estimate Grain Sorghum Yield and Evapotranspiration
Authors: Ajayi Ayodele Ebenezer , Olufayo Ayorinde A.
Published: July 2010

This study was performed to examine the relationship between canopy temperature (Tc)–based stress indices and grain yield and evapotranspiration (ET) of sorghum [Sorghum bicolor (L.) Moench]. The crop was subjected to 14 differentially irrigated treatments of which two were controls maintained at well‐watered and dry conditions during three consecutive years. Soil water content and Tc were measured, and relationships between Tc–based stress indices [stress degree day (SDD), temperature stress day (TSD), and crop water stressed index (CWSI)] and yield as well as ET were examined. The Tc–air temperature (Ta) difference varied from −2 to +8°C in the stressed treatments and maintained a negative value for most of the time in the well‐watered treatment. The relationship between Tc − Ta and vapor pressure deficit, commonly referred to as baseline in the determination of CWSI, was examined on function of wind speed and global solar radiation. Although observations showed that Tc can be influenced by climatic condition, this study confirmed that it can serve as a useful indicator of water stress in the case of sorghum. High correlation found between Tc–based stress indices TSD, SDD, and CWSI and ET as well as grain yield suggest the possibility of using these relationships for predictive purposes.
Simultaneous Tests and Confidence Intervals for the Evaluation of Agricultural Field Trials
Authors: Frömke Cornelia , Bretz Frank
Published: July 2010

Agricultural designs commonly involve the simultaneous analysis of more than two factors and more than two levels for each factor. This article addresses the use of adequate statistical tests while taking multiplicity into account. Two data sets and their appropriate statistical analysis are presented as illustrative examples. The first data set is a split‐plot design, with two fixed factors and a random block factor, and the second data set is a two‐factor factorial complete randomized design. Two SAS macros are presented to analyze the data sets properly in terms of the multiplicity problem, and these macros compute simultaneous confidence intervals and multiplicity‐adjusted p values. The two macros, called %SimultanTests and %SimultanIntervals, are based on exact evaluations of the underlying multivariate t distribution and are extensions of the published macros %SimTests and %SimIntervals. The macros are widely applicable tools, which can be used with relatively little effort for the analysis of many agricultural designs.
Weed Seedbank Dynamics in Three Organic Farming Crop Rotations
Authors: Teasdale John R. , Mangum Ruth W. , Radhakrishnan Jay , Cavigelli Michel A.
Published: July 2010

Weed management is a primary concern of organic farmers. Crop rotation is an important potential management approach for regulating weed seed populations in the soil of organic farming systems. This research was conducted to determine the effect of three organic crop rotations on the weed seedbank during the first 6 yr of a long‐term cropping systems experiment at Beltsville, MD. The rotations consisted of (i) a 2‐yr corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation, (ii) a 3‐yr corn–soybean–wheat (Triticum aestivum L.) rotation, and (iii) a 4‐yr corn–soybean–wheat–red clover (Trifolium pratense L.)/orchardgrass (Dactylis glomerata L.) hay rotation. Weed seed populations were determined by a greenhouse emergence assay using soil samples taken in the early spring of each year. The seedbanks of smooth pigweed (Amaranthus hybridus L.) and common lambsquarters (Chenopodium album L.) preceding corn were usually lower following the hay years of the 4‐yr rotation or the wheat year of the 3‐yr rotation than following the soybean year of the 2‐yr rotation. However, annual grass seedbanks preceding corn tended to be higher following the hay years of the 4‐yr rotation than following the wheat year of the 3‐yr rotation or the soybean year of the 2‐yr rotation. Seedbanks in the 3‐ and 4‐yr rotations were similar to those of the 2‐yr corn–soybean rotation (higher smooth pigweed and common lambsquarters and lower annual grass) when these longer rotations began with a corn–soybean sequence than with other sequences. Sequences beginning with hay had lower smooth pigweed and common lambsquarters seedbank populations than all other sequences. The seedbank in spring significantly predicted weed abundance at maturity in corn in at least 2 of 4 yr for all species. Results show that longer rotations with more phenologically diverse crops can reduce seedbank populations and abundance of important annual broadleaf weed species in organic production systems.
Forage Yield and Nutrient Uptake of Warm‐Season Annual Grasses in a Swine Effluent Spray Field
Authors: McLaughlin M. R. , Fairbrother T. E. , Rowe D. E.
Published: July 2010

Five warm‐season annual grasses were compared for dry matter (DM) yield and nutrient uptake alongside bermudagrass [Cynodon dactylon (L.) Pers.] on a Brooksville silty clay (fine, montmorillonitic, thermic Aquic Chromuderts) in a field that had swine (Sus scrofa) effluent applied through a center pivot sprinkler system. Annuals were browntop millet [Panicum ramosum (L.) Stapf in Prain], pearl millet [Pennisetum glaucum (L.) R. Br.], sudangrass [Sorghum bicolor (L.) Moench], sorghum–sudan, [Sorghum bicolor (L.) Moench], and crabgrass [Digitaria sanguinalis (L.) Scop.]. Grasses were tested in 3 yr (1999–2001), but results in 2000 were incomplete due to poor growing conditions. In 1999 (establishment year for bermudagrass) sorghum–sudan had the highest DM yield (18.9 Mg ha−1) and P uptake (50.3 kg ha−1). In 2001, sorghum–sudan DM yield (20.6 Mg ha−1) and P uptake (56.3 kg ha−1) were equivalent to established bermudagrass (21.3 Mg ha−1 and 56.1 kg ha−1, respectively). In 2001 sudangrass and pearl millet DM yields (17.4 and 15.7 Mg ha−1, respectively) were equal to and lower than sorghum–sudan, but P uptake of pearl millet (49.5 kg ha−1) did not differ from sorghum–sudan, due to the high P concentration (3.2 g kg−1) in pearl millet. Browntop millet and crabgrass DM yields and P uptake were less than those of sorghum–sudan in both years. Sorghum–sudan and pearl millet were higher in DM yield and P uptake than the other annuals in both years, equal to established bermudagrass, and therefore should be the most useful in nutrient management hay systems in the southeastern USA.
Calibrating the Leaf Color Chart for Nitrogen Management in Different Genotypes of Rice and Wheat in a Systems Perspective
Authors: Shukla Arvind K. , Ladha Jagdish K. , Singh V. K. , Dwivedi B. S. , Balasubramanian Vethaiya , Gupta Raj K. , Sharma S. K. , Singh Yogendra , Pathak H. , Pandey P. S. , Padre Agnes T. , Yadav R. L.
Published: July 2010

Low N use efficiency (NUE) continues to be a problem in the rice (Oryza sativaL.)–wheat (Triticum aestivumL.) cropping system. The leaf color chart (LCC)–based real‐time N management can be used to optimize/synchronize N application with crop demand or to improve existing fixed split N recommendations. We conducted a field experiment during 2001–2003 at Modipuram, India, to determine the threshold LCC values for N application in rice and wheat, assess the need for basal N application, calibrate the LCC with a chlorophyll meter (SPAD), and work out the economics of rice–wheat systems. Treatments consisted of LCC scores of 2 to 5 for different cultivars of rice and wheat and were compared with the zero‐N control and a recommended fixed‐time N splitting. In rice, LCC ≤ 3 for ‘Basmati‐370’, 4 for ‘Saket‐4’, and 5 for ‘Hybrid 6111/PHB‐71’ produced higher yield and NUE than recommended N splits. In wheat, maintenance of LCC ≤ 4 required 120 kg N ha−1, which produced higher grain yield, N uptake, and NUE than that of recommended N splits. Chlorophyll meter reading and crop growth rate (g m−2day−1) at 15 d after transplanting in rice and 21 d after seeding in wheat were not significantly different with or without basal N application, indicating that basal N application in rice and wheat was not necessary in soils having relatively high indigenous N supply. Both LCC and SPAD readings (r= 0.84 to 0.91) were highly correlated in rice and wheat. Net returns were 19 to 31% higher in LCC‐based N management than in fixed‐time N application for rice–wheat cropping.