bluuebunny/crossref_metadata_2025 huggingface dataset:
Tillage Systems for Cotton on Silty Upland Soils
Authors: Triplett Glover B. , Dabney Seth M. , Siefker James H.
Published: July 2010

No‐tillage systems for cotton (Gossypium hirsutum L.) production on sloping, upland sites have not been widely adopted in the Mid‐South of the USA, even though conventional cotton production creates a serious erosion hazard. A field study was established following sod on a site with loess soils to evaluate tillage system effect on cotton yield and earliness. The sod was tilled prior to establishment of treatments, which included conventional (chisel, disk, bed, cultivate), ridge till (remove ridge tops at planting, cultivate postemergence to rebuild ridges), no‐tillage [wheat (Triticum aestivum L.) cover seeded following cotton harvest, killed prior to planting], and minimum tillage (one pass with a mulch finisher prior to planting, cultivate postemergence). During the first year of the study, no‐tillage cotton yields were lower and maturity delayed compared with conventional tillage. During Years 3 to 5, no‐tillage crop yields were 18 to 42% greater and crop maturity was 6 to 10 d earlier than conventional tillage. Minimum tillage yields were similar to conventional tillage while ridge tillage was lower in two of the last 3 yr of the study. Results of this study indicate viable no‐tillage production systems for cotton can be developed for highly erosive loess soils in the Mid‐South.
Irrigation Starting Time Effects on Cotton under High‐Frequency Irrigation
Authors: Wanjura Donald F. , Mahan James R. , Upchurch Dan R.
Published: July 2010

Deciding when to begin irrigating cotton (Gossypium hirsutum L.) is difficult because the positive effect of eliminating water stress may be offset by the negative effect of lowered soil temperature. Different starting times for high‐frequency drip irrigation of cotton were investigated in a field having Olton clay loam soil (fine, mixed, thermic Aridic Paleustolls). Early irrigation (EI), started when seedlings had 3 mainstem nodes, was compared with delayed irrigation (DI‐L), started at squaring when there were 7 mainstem nodes. Another delayed irrigation treatment (DI‐H) received an initial large irrigation that equaled the cumulative amount of water applied by that time to the EI treatment. During the early irrigation period, 130 mm of water was applied in 1993 and 120 mm in 1994. Average soil temperature in the top 1000 mm during the early irrigation period was 25°C in the EI treatment, compared with 27°C in the DI treatment. During the late irrigation period, the average soil temperature was 24.5°C for EI and 25.5°C for DI. At first bloom, plants were 30 mm taller in 1993 and 70 mm taller in 1994 in the EI irrigation treatment, compared with the DI‐L treatment. Lint production was greatest in the DI‐L treatment in both years (1548 and 1630 kg ha−), compared with the DI‐H treatment (1467 and 1460 kg ha−1) and the EI treatment (1447 and 1481 kg ha−1). Water use efficiency, based on the total of irrigation and rainfall, averaged 3.33, 2.42, and 2.36 kg lint ha‐mm−1 for the DI‐L, DI‐H, and EI irrigation treatments, respectively. Initiating automated irrigation scheduling before squaring in cotton increased seedling height but decreased lint yield and the efficiency of use of total applied water.
Application of SORKAM to Simulate Shattercane Growth Using Forage Sorghum
Authors: Retta Amare , Vanderlip Richard L. , Higgins Randall A. , Moshier Loren J.
Published: July 2010

Shattercane [Sorghum bicolor (L.) Moench] is a serious weed problem. Few methods are available to assess the impact of shattercane competition on crop growth and yield. This study evaluated model sensitivity to variations in light, water, and plant density and assessed the applicability of the SORKAM model for simulating forage sorghum (used to represent shattercane) growth and development. Sensitivity analysis of SORKAM to photosynthetically active radiation (50, 75, and 100% of actual); water (50, 75, and 100% of actual precipitation, and no water stress); and plant densities of 3, 6, 12, 24, 48, and 96 plants m−2 was performed. ‘Rox Orange’ forage sorghum (used to represent shattercane) was grown at three densities, under irrigated and dryland environments over a 3‐yr period. Experiments were conducted on Eudora (coarse‐silty, mixed, mesic Fluventic Hapludoll) and Kahola silt loam (fine‐silty, mixed, mesic Cumulic Hapludoll) soils, in Manhattan, KS. The sensitivity analysis showed that SORKAM responded to a broad range of light, water, and plant density environments, with significant light by water interaction for biomass, and light by density interaction for biomass, leaf area index (LAI), and tillering. The SORKAM model simulated growth of Rox Orange from inputs of weather, soil, and plant data were compared with measured values. There was good agreement between simulated and measured LAI through 60 d after planting (r2 = 0.82, intercept not significantly different from 0, and slope = 0.83). Accurate estimation of LAI during this period of vegetative growth is important, because LAI determines the competition between a crop and shattercane for light and water. Agreement of measured and simulated biomass was good for low plant densities (slope and intercept not significantly different from 1 and 0 with high r2 = 0.78), with progressively greater underestimation at higher densities. Tiller number was generally underestimated, with no apparent correlation to model under‐ or overestimation of LAI or biomass. The sensitivity analysis and comparison of measured and simulated LAI indicates that the SORKAM model can be used to assess Rox Orange (shattercane) competition.
Effects of Water Deficit Stress on Competitive Interaction of Peanut and Sicklepod
Authors: Moreshet Samuel , Bridges David C. , NeSmith D. Scott , Huang Bingru
Published: July 2010

One of the potentially deleterious effects of weeds on crop production is competition for water. In this study, competitive interactions between peanut (Arachis hypogaea L.) and sicklepod (Senna obtusifolia L.) were investigated. The two species were grown alone and mixed in a glasshouse in 118‐L barrels (0.65 deep and 0.48 m wide) filled with a Molena sandy soil (sandy, mixed, thermic Psammentic Hapludults). Treatments were either continuously irrigated (WET) or periodically dried (DRY). Measurements included daily soil water content (τ), continuous water uptake, stomatal conductance (g), leaf xylem water potential (Ψ1) and leaf osmotic potential. Water uptake and g were well correlated to τ. With both species, water uptake, g, and Ψ1 all declined when τ in the top half of the barrel was approximately one‐third of the available water (5.8 to 7.4% v/v; equivalent soil water potential, Ψs, −0.20 and −0.08 MPa). The τ‐values at which water uptake and g began to decline (here called inflection points) were always lower for peanut (5.9 to 6.1%; Ψs = The τ‐values at) than for sicklepod (7.4 to 7.5%; Ψs = − 0.08 to − 0.07 MPa). Ψ1 was similar for the two species. The inflection points of water uptake, g, and Ψ1 for both species were always higher when related to τ‐values in the bottom half of the barrel (8.6% to 13.1%, Ψs = − 0.04 and − 0.005 MPa) than when related to τ in the top half of the barrel. This response occurred even though the fraction of fine root length density in the bottom half was more than 45% of the total fine root length density in the DRY treatment of sicklepod and both species mixed. Significant osmotic adjustment was detected in both species following water deficit stress. At full turgor, leaf osmotic potential of all WET treatments reached − 0.99 MPa; at zero turgor, it reached −1.12 MPa. For the DRY treatments, leaf osmotic potential at full turgor dropped to −1.22 and −1.24 MPa in sicklepod and peanut, respectively; at zero turgor, it dropped to − 1.31 and − 1.34 MPa in sicklepod and peanut, respectively, but the difference between species was not significant. As the soil dried, water use by peanut mixed was significantly higher than sicklepod mixed. It appears that peanut can use more water under water deficit stress and can recover faster than sicklepod in a mixed community of the two species.
The Quest for Balance in Crop Modeling
Authors: Monteith John L.
Published: July 2010

Crop models habitually run ahead of the measurements needed for rigorous calibration and validation. The treatment of key physiological processes is often very uneven, and the availability of microcomputers encourages modelers to develop complex schemes providing output that is unqualified by errors or uncertainties. Crop models are potentially powerful tools, but they should be used in a more disciplined way.
Aerodynamic Characteristics of Standing Corn Stubble
Authors: Sauer Thomas J. , Hatfield Jerry L. , Prueger John H.
Published: July 2010

Maintenance of crop residues on the soil surface is promoted as a management practice for reducing soil erosion by wind and water. Crop residue on the soil surface, however, also influences turbulent exchange processes that affect surface water and energy balances. At present, there are very limited data on the aerodynamic properties of residue‐covered surfaces. The objective of this research was to derive estimates of the aerodynamic properties (momentum roughness length z0, zero‐plane displacement d, and drag coefficient Cd) of fields with standing corn (Zea mays L.) stubble. Wind speed and air temperature measurements were made at six heights above two no‐tillage fields near Ames, IA, in the spring and fall of 1994 and in the spring of 1995. Both sites had standing corn stubble approximately 0.3 m tall at a density of greater than 60 000 stalks ha −1 and nearly 95% residue cover. An iterative, least‐squares linear regression technique was applied to wind profiles obtained under neutral atmospheric conditions to determine z0, d, and the friction velocity (u.). Mean values of z0 and d for each of the three measurement periods varied from 11.8 to 24.3 and 119 to 169 mm, respectively. The ratios z0/hs and d/hs, where hs is the mean stubble height, averaged 0.058 and 0.53, respectively, for all profiles. The magnitude of zo and d and their weak dependence on wind speed are consistent with turbulent flow over a surface with sparse, rigid roughness elements. The z0 and Cd were higher for the fall measurement period, suggesting that the loose, fresh residue presented a comparatively rough surface that was then smoothed by weathering and compaction beneath snow.
Long‐Term Tillage, Crop Rotation, and Nitrogen Fertilizer Effects on Wheat Yield under Rainfed Mediterranean Conditions
Authors: López‐Bellido L. , Fuentes M. , Castillo J. E. , López‐Garrido F. J. , Fernández E. J.
Published: July 2010

The combined long‐term effects of tillage method and crop rotation on crop yield have not been studied in rainfed systems under Mediterranean climates. A field study was conducted from 1988 to 1994 to determine the effects of tillage (TILL), crop rotation and (ROT) N fertilizer on wheat (Triticum aestivum L.) yield in a rainfed Mediterranean region. Tillage treatments include no tillage (NT) and conventional tillage (CT). Crop rotations were wheat‐sunflower (Helianthus annuus L.) (WS), wheat‐chickpea (Cicer arietinum L.) (WCP), wheatfababean (Vicia faba L.) (WFB), wheat‐fallow (WF), and continuous wheat (CW), with N fertilizer rates of 50, 100, and 150 kg N ha−1. A split‐split plot design with four replications was used. Differences in rainfall during the growing season had a marked effect on wheat yield. Amount of rainfall during the vegetative period for wheat (November‐February) was highly correlated with yield because of the high water‐retention capacity of Vertisols (Typic Haploxerert). In dry years, wheat yield was greater under NT than under CT; the opposite was true in wet years. The TILL ✕ ROT interaction was also significant in the drought years; the wheat yield under NT was greater for CW and the WFB and WF rotations than under CT. Wheat yields ranked by crop rotation were: WFB > WF >> WCP > WS >> CW. Wheat did not respond to N fertilizer when rainfall was below 450 mm during the growing season. Using these results strategies can be developed for establishing the N fertilizer rate applied to wheat as a function of rainfall, the preceding crop, and residual N in soil in order to optimize wheat yield and reduce nitrate pollution to groundwater.
Tillage and Crop Residue Effects on Corn Production in Quebec
Authors: Burgess M. S. , Mehuys G. R. , Madramootoo C. A.
Published: July 2010

Reduced tillage is often recommended to decrease soil degradation and erosion associated with intensive row cropping. This study assessed the effects of different tillage and crop residue levels on corn (Zea mays L.) yields and related factors on a 2.4‐ha site in southwestern Quebec over a 3‐yr period. The soil, a Typic Endoaquent, consisted of sandy loam or loamy sand (mean depth, 46 cm) overlying clay, with subsurface drains at the 1.2‐m depth. Treatments, begun in fall 1991, consisted of no‐till (NT), reduced tillage (RT; disked in fall and spring), and conventional tillage (CT; moldboard‐plowed in fall, disked in spring), in combination with two crop‐residue levels: no residue (− R; grain and stover removed at harvest, as for silage corn) and with residue (+ R; stover left on site at harvest, as for grain corn). High crop‐residue mulches resulted from NT ÷ R (77–97% of soil surface covered), RT + R (45–92%), and at times NT −R (8–35%), potentially protecting the soil from erosive forces. Seedling emergence was delayed (1992, 1993) or partly suppressed (1994) in NT + R, and was also delayed in CT + R in 1992 and 1993, and in CT−R and RT ÷ R in 1993. Final populations were affected only in 1994. In − R (silage) plots, yields with NT and RT were either greater (1992) or the same as their CT counterparts. On + R (grain) plots, grain, stover, and total yields were lower with NT in 1992 and 1994, due in part to difficulties in planting through the residue mulch, while RT reduced grain, stover, and total yields in 1992 and stover and total yields in 1993. Thus, for silage‐corn production, NT and RT may offer economically viable alternatives to CT, although the use of disking for a RT system provides almost no protective residue cover. In continuous grain corn, high residue buildup with NT and RT requires special attention to seeding technique or yield losses may result.
Corn Yield is Equal in Conventional, Reduced, and No Tillage after 20 Years
Authors: Kapusta George , Krausz Ronald F. , Matthews Joseph L.
Published: July 2010

Reduced tillage has increased dramatically over the past several years and is expected to continue to increase in the future. Continuous no‐till may become a popular tillage system with growers to facilitate compliance with government programs to control soil erosion. The objective of this research was to evaluate the long‐term effects of four tillage systems and five fertilizer regimes on corn (Zea mays L.) yield. A 20‐yr continuous‐corn tillage ✕ fertility study was conducted from 1970 to 1990 on an Ebbert silt loam (fine‐silty, mixed, mesic Argiaquic Argialbolls), an imperfectly drained soil at the Belleville Research Center, Belleville, IL. Starter fertilizer did not increase corn height within a tillage system. Height was greater in no‐till compared with conventional till (moldboard plow), reduced till (chisel plow), or alternate till (2 yr no‐till, 1 yr moldboard plow) with or without a starter fertilizer. There was no difference in population among tillage systems due to fertilizer treatment. Corn population was lower in no‐till compared with conventional till regardless of fertilizer treatment. Starter fertilizer did not increase yield in any tillage system. Corn yield averaged 5 to 7% lower in no‐till compared with conventional till or reduced till where a starter fertilizer was applied. There was no difference in yield among tillage systems when NPK was broadcast. Corn yield was equal in conventional till, alternate till, reduced till, and no‐till with fertilizer applied broadcast on an imperfectly drained soil. Continuous no‐till with an imperfectly drained soil does not reduce corn yield.
Groat Yield and Plant Stand Structure of Naked and Hulled Oat under Different Nitrogen Fertilizer and Seeding Rates
Authors: Peltonen‐Sainio Pirjo
Published: July 2010

Grain yield of naked oat (Avena sativa var. nuda L.) is lower than that of hulled oat mainly due to reduced seedling emergence, fewer spikelets per panicle, and more grains per spikelet. This study was conducted in the field to evaluate management possibilities of reducing these undesirable traits of naked oat by adjusting seeding rate and N fertilizer application rate, thereby increasing groat yield. Studies were conducted at the Viikki Experimental Farm, University of Helsinki, Finland, in 1993 and 1994. Two N fertilizer rates (80 and 120 kg N ha−1) and five seeding rates (400, 500, 600, 700, and 800 viable seeds m−2) were used. Grain and groat yield and 24 morphophysiological traits of three naked and two hulled lines were compared. The highest yielding naked line, Rhiannon, produced approximately 9% higher groat yield and 4% more groat per panicle than the most popular Finnish hulled oat line, Veli. The same groat yield in naked lines and Veli, when measured across all treatments, may result from modest ( ≈ 2%) differences in seedling emergence. Use of seedling emergence instead of germination percent to determine planting density, and seed treatment with a fungicide, possibly contributed to uniform emergence. Naked lines tillered slightly more than hulled lines, and tiller contribution to leaf area index was higher at lower seeding rates. Use of high seeding rates reduced both number of spikelets and grains per panicle without having consistent effects on number of tertiary grains per spikelet. Number of grains per spikelet was not affected by N fertilizer rate. There was no marked advantage for using higher seeding rates and N fertilizer rates for naked lines. However, the capacity of naked lines to produce panicles through tillering compensates for reduced seedling emergence and an undesirably high grain number associated with a low number of spikelets per panicle.
Intermittent Shade Effect on Gas Exchange of Cotton Leaves in the Humid Southeastern USA
Authors: Bauer Philip J. , Sadler E. John , Frederick James R.
Published: July 2010

Convective cumulus clouds intermittently shade growing plants on most days during the summer months in the southeastern USA. Previous research indicates a significant delay in the recovery of stomatal conductance (gs) of cotton (Gossypium hirsutum L.) leaves following a period of shade. Our objective was to determine the effect of shade on leaf net CO2 exchange rate (CER) and gs of three cotton cultivars. We monitored CER and gs of greenhouse‐ and field‐grown cotton before, during, and after shading plants for up to 9 min at photosynthetically active radiation (PAR) levels of <300 μmol quanta m−2 s−1. The three cultivars had the same gas exchange response to shade. With the imposition of a 6‐min shade on greenhouse‐grown plants at 7 weeks after planting (WAP) gs of uppermost fully expanded leaves fell 43%. Two weeks later, a 6‐min shade reduced gs of uppermost fully expanded leaves by 97%. Under field conditions, a 9‐min shade reduced gs by 35% early in the cutout period (cessation of vegetative growth) in 1992 and 42% late in the cutout period in 1994. Under both greenhouse and field growing conditions, the low PAR levels with shade reduced CER to near 0 μmol CO2 m−2 s−1. Recovery of CER to preshade levels after the shade was removed coincided with the rate of recovery of gs. In the greenhouse‐grown plants, recovery of CER to preshade levels following 6 min of shade did not occur until 7 min (at 7 WAP) and 10 min (at 9 WAP) after the shade was removed. Field‐grown leaves needed only 4 min to recover to preshade levels of CER and g2 following 9 min of shade. The results suggest that, following a brief shade period, field‐grown cotton leaves reacclimate within 4 min, while leaves on greenhouse‐grown plants may take longer.
DIALLEL‐SAS: A SAS Program for Griffing's Diallel Analyses
Authors: Zhang Yudong , Kang Manjit S.
Published: July 2010

Diallel mating designs are generally used to obtain estimates of genetic effects for a fixed set of parental lines (fixed effects) or to estimate general combining ability (GCA) and specific combining ability (SCA) variance components from a set of randomly chosen parental lines (random effects) from multiple‐environment experiments. Published computer programs for diallel analyses do not provide a partition of F1 hybrids ✕ environments interaction into GCA ✕ environments, SCA ✕ environments, and reciprocal ✕ environments components for Griffing's Methods 1 and 3, and into GCA ✕ environments and SCA ✕ environments components for Griffing's Methods 2 and 4. Existing programs for Methods 1 and 3 also do not partition reciprocal effects into maternal and nonmaternal effects. This paper reports the development of a comprehensive SAS program (DIALLEL‐SAS) for partitioning interactions between environments (years and/or locations) and F1 hybrids. DIALLEL‐SAS can be run on any microcomputer with SAS, as well as on mainframe computers installed with SAS via UNIX or TSO. The DIALLEL‐SAS output includes (i) mean squares for environments, F1 hybrids, F1 hybrids ✕ environments, GCA, SCA, reciprocal, maternal, nonmaternal, GCA ✕ environments, SCA ✕ environments, reciprocal ✕ environments, maternal ✕ environments, nonmaternal ✕ environments, (ii) estimates of GCA and maternal effects for each parental line, and (iii) estimates of SCA, nonmaternal, and reciprocal effects for each F1 hybrid.
Recovery of Fertilizer Nitrogen Applied to Burley Tobacco
Authors: MacKown Charles T. , Sutton Tommy G.
Published: July 2010

The high cash value of burley tobacco (Nicotiana tabacum L.) may lead to ineffective excess fertilization of the crop. The effects of N management on fertilizer N use efficiency by burley tobacco and recovery of residual fertilizer N by a winter cover crop were determined. Tobacco was grown in 1993 at two locations with 0 to 336 kg N ha−1 broadcast applied before transplanting or 168 kg N ha−1 sidedressed at onset of rapid growth (≈ 5 wk after transplanting). Seasonal recoveries of 15N‐depleted fertilizer N were determined in aboveground tissues of the tobacco crop. The amount of labeled fertilizer N recovered at harvest (29 to 124 kg N ha−1) increased with increasing amounts of N applied, but fertilizer N use efficiency was constant at 36.6 ± 0.9% for broadcast applications. Sidedress N enhanced labeled fertilizer N recovery (43 to 54% of applied N, depending on location), even though total aboveground dry matter was equal to or 12% less than that of plants grown with the same amount of N applied by broadcast. Recovery of residual labeled fertilizer N in the cover crop ranged from 2 to 7% of applied N and was greatest for the highest amount of N applied. Fertilizer N recoveries estimated by the difference method equaled those of the 15N method at 5 wk after transplanting. At 13 wk after transplanting, the difference method, particularly for applications of 84 and 168 kg N ha−1, overestimated fertilizer N recoveries relative to the 15N method, and is unlikely to provide an accurate measure of fertilizer N use by burley tobacco across a wide range of N applications. Reducing the amount of broadcast applied fertilizer to give a 10% decrease in air‐cured leaf yield would decrease the unaccounted fertilizer N by 80 to 115 kg N ha−1, depending on location. As compared with broadcast application of fertilizer N before transplanting, drill banding the N at about 5 wk after transplanting would equal or further decrease unaccounted amounts of fertilizer N.
Subsoil Nitrate Uptake by Grain Pearl Millet
Authors: Menezes Romulo S. C. , Gascho Gary J. , Hanna Wayne W. , Cabrera Miguel L. , Hook James E.
Published: July 2010

Pearl millet [Pennisetum glaucum (R.) Br.] is a high‐quality grain crop that can that can be grown without irrigation during hot, dry summers in the southeastern United States. The N rate required for optimum pearl millet grain yield varies widely in published studies, possibly because of variability in residual soil N from the subsoil. Field studies were conducted in the southern Coastal Plain at Tifton, GA, on a Tifton loamy sand (fine‐loamy, siliceous, thermic Plinthic Kandiudult) with nitrate accumulations near subsoil plinthite. The objective was to determine if pearl millet can extract N from acidic, relatively impermeable subsoils. Nitrate N (1 M KCl‐extractable) was 4 mg kg−1 in the surface 0.6 m, 1 mg kg−1 in the next 0.6 m, and 6 mg kg−1 from 1.2 to 1.5 m. We fertilized pearl millet field plots with two levels of N (0 and 168 kg ha−1) and studied root development during the growing seasons in 1993 and 1994. Soil cores were taken 40 d after planting to a depth of 1.2 m, separated into 0.3‐m depth segments, and root length density was measured. Roots were found in the deepest segments. Nitrogen fertilization increased the proportion of the root length density found in the surface soil in one year. We also injected 15N as 60% atom l5N‐enriched KNO3 at a depth of 1 m at 30 and 40 d after planting. At physiological maturity, atom % 15N abundance in the plants ranged from 10.1 to 12.0 where 15N was injected and was near natural abundance where no 15N was injected. These results indicate that pearl millet can extract N from 1 to 1.2 m in an acidic and impermeable subsoil.
Modeling a Rye Cover Crop and Subsequent Soybean Yield
Authors: Wagner‐Riddle Claudia , Gillespie Terry J. , Hunt Leslie A. , Swanton Clarence J.
Published: July 2010

Soybean [Glycine max (L.) Merr.] can be no‐till seeded in the spring following a killed rye (Secale cereale L.) cover crop. A shortage of rain can affect soybean yields, depending on the timing of killing and the amount of mulch produced. Our main objective was to incorporate the effect of a rye mulch on soil water content into a soybean growth model (SOYGRO). The use of a wheat (Triticum aestivum L.) growth model (CERES‐Wheat) for rye mulch production calculations and SOYGRO for predicting yields under no‐mulch and mulch conditions were evaluated. The water balance subroutine of SOYGRO was modified to account for the effect of a rye mulch on soil water content due to mulch albedo, rain interception, and transmissivity of solar radiation. Data from previous experiments at Delhi (Psammentic Hapludalf soil), and Woodstock (Typic Hapludalf) in Ontario, Canada, were used to evaluate these modifications and yield predictions. Mulch production was described well by CERES‐Wheat (r2 = 0.96). The modified SOYGRO model improved soil water content calculations relative to the original model (r2 = 0.67 vs. 0.58, root mean square error = 0.028 vs. 0.064 m3 m−3). Simulated soybean yields were within 1 SD of measured values. In agreement with field measurements, the simulated effect of mulch did not increase soybean yields, and modification of SOYGRO to include mulch effects did not change yield predictions (r2 = 0.83 vs. 0.81) when no prolonged drought occurred. The simple mulch model incorporated into SOYGRO was adequate to model the effect of rye mulch on soybean growth. The use of CERES‐Wheat and the modified SOYGRO model in sequence under hypothetical drier weather conditions was demonstrated.
Cropping and Tillage Systems for Dryland Grain Production in the Southern High Plains
Authors: Jones Ordie R. , Popham Thomas W.
Published: July 2010

Low precipitation and high evaporative potential limit yields of dryland crops in the semiarid Southern High Plains. Improved residue management can reduce evaporation and improve water conservation. We compared no‐tillage (NT) and stubble mulch (SM) residue management effects from 1984 to 1993 on leveled minibenches at Bushland, TX, using winter wheat (Triticum aestivum L.)‐fallow (WF), continuous wheat (CW), wheat‐sorghum [Sorghum bicolor (L.) Moench]‐fallow (WSF), and continuous sorghum (CS) systems. The soil was a Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll). Our objective was to quantify and compare soil water storage, crop water use, and grain production in order to identify the most water‐efficient production system. Relative to SM management, NT management of wheat residues increased average soil water contents at planting of the next crop by 22 mm with WSF, 15 mm with WF, and 29 mm with CW; it was not as effective with sorghum residues. Mean grain yields were not affected by residue management on any cropping system, because the additional water stored with NT management was slight in relation to seasonal evapotranspiration. Cropping systems had major effects on grain yield and production. Fallow systems (WSF, WF) normally resulted in higher yields than the corresponding annual cropping system (CW, CS). However, when grain production was adjusted to an annual basis including fallow time, the CS system was most efficient at using precipitation, producing 92% more grain than WSF, 240% more than CW, and 320% more than WF. Grain production was more than twice as great with sorghum than with wheat, due to greater biomass production and a 33% greater harvest index. Although wheat is the major dryland crop in the Southern High Plains, sorghum seems much better adapted to the region's predominant pattern of late spring‐summer rainfall.
Grain Yield is Reduced More by Weed Interference in an Old than in a New Maize Hybrid
Authors: Tollenaar Matthijs , Aguilera Alberto , Nissanka Sarath P.
Published: July 2010

Grain yield improvement of maize (Zea mays L.) hybrids in Ontario has been associated with increased stress tolerance of newer hybrids. This study was conducted to assess the effect of low soil N, weed interference, and soil water deficit on dry matter accumulation and grain yield of an older and a more recent hybrid. Studies were carried out at the Elora Research Station in 1992, 1993, and 1994 on a London loam (Aquic Hapludalf) that had been tile drained. The experiment was arranged in a split‐split‐split‐plot design with four replications. Treatments consisted of two soil‐N levels (70 and 225 kg ha−1), weedfree all season and weedy from the 3‐ to 4‐leaf stage of maize, irrigation and no irrigation, and the hybrids ‘Pioneer 3902’ (new) and ‘Pride 5’ (old). Maize phenology, dry matter accumulation, grain yield, stomatal conductance, leaf chlorophyll fluorescence, and leaf chlorophyll content were measured. Irrigation generally did not influence the measured parameters. Silking date and stomatal conductance during the grain‐filling period were affected less by low soil N and weed interference in Pioneer 3902 than in Pride 5. Aboveground dry matter at silking and maturity was reduced about 20% by single stresses of low soil N and weed interference and about 55% by the combination of both stresses. Hybrid × stress treatment interactions for dry matter were not significant. The reduction in grain yield due to weed interference was 21% greater in Pride 5 than in Pioneer 3902. The hybrid × N interaction for grain yield was not significant, because a smaller reduction in harvest index due to N stress in the new than in the old hybrid was offset by a larger reduction in dry matter accumulation during the grain‐filling period. The differential response of the two hybrids to stress was greatest during the silking period, as indicated by the greater reduction in harvest index and kernel number in the old than in the new hybrid due to stress.
Fallow Management Effects on Soil Water Storage and Wheat Yields in the Pacific Northwest
Authors: Pannkuk Chris D. , Papendick Robert I. , Saxton Keith E.
Published: July 2010

Conservation tillage practices are adopted by farmers to control soil erosion and in some cases to reduce production costs. Conventional tillage practices usually rely on extensive tillage to control weeds and conserve water. In other cases, grazing animals may be used to control weeds and utilize crop residues for animal fodder on the fallowed land. These intensive systems leave the soil surface bare and susceptible to erosion. A five‐year study was conducted in the winter wheat (Triticum aestivum)‐fallow area of eastern Washington to evaluate the effects of tillage, weed control, and residue management on soil water storage and wheat yields. Tillage treatments were (i) conventional (early spring sweep and summer cultivation), (ii) delayed spring (late spring sweep and chemical weed control), and (iii) no‐till (chemical fallow). Residue management treatments were (i) all residues removed at the beginning of the 22‐mo fallow, (ii) all residues and vegetation removed after the first winter rainy season, and (iii) residues not removed. Weed control treatments were (i) weeds not controlled during the first winter rainy season but controlled thereafter and (ii) weeds controlled throughout the fallow period. Soil water storage was greater every year where crop residues were not removed, or removed after the first winter of the fallow period, compared with residue removal at the beginning of the 22‐mo fallow. Weedy fallow (weeds allowed to grow during the first winter rainy season) had no effect on fallow efficiency or wheat yields compared with fallow with weed control. Wheat yields were increased in one year out of five by the retention of surface residues and in one year by tillage and, thus, for the most part did not reflect differences in water storage efficiencies. Weedy fallow provided greater residue cover through erosive periods, but did not adversely affect soil water storage and wheat yields compared with fallow with weed control.
Validation of the Soil Temperature Subroutine HEAT in the Cotton Simulation Model GOSSYM
Authors: Khorsandi Farhad , Boone Mariquita Y. L. , Weerakkody Govinda , Whisler Frank D.
Published: July 2010

The empirical soil temperature subroutine of the cotton simulation model GOSSYM did not perform well under bare and cotton‐cropped (Gossypium hirsutum L.) surface conditions in the field. Therefore, it was replaced by a mechanistic soil temperature subroutine called HEAT. The HEAT subroutine was validated against soil temperature data collected in the field under bare and cotton‐cropped surface conditions, and was compared with the empirical TMPSOL subroutine of GOSSYM. Soil temperatures were collected in the field under bare and cotton‐cropped surface conditions at two locations (row and furrow) and four depths (5, 10, 25, and 60 cm) during the growing seasons of 1991 and 1992. Under bare surface conditions, HEAT underpredicted the average daily soil temperatures by 1 to 7°C at all locations and depths. However, under cotton‐cropped surface conditions, HEAT calculated the soil temperature adequately, especially after canopy closure. Under bare surface conditions, the temperatures calculated by TMPSOL were closer to the measured values than those calculated by HEAT, but were still beyond the standard deviations of the measured values. It is recommended that the TMPSOL subroutine in GOSSYM be replaced by the HEAT subroutine.
Kill Date of Vetch, Rye, and a Vetch—Rye Mixture: II. Soil Moisture and Corn Yield
Authors: Clark Andrew J. , Decker Alvin M. , Meisinger John J. , McIntosh Marla S.
Published: July 2010

Spring cover crop kill date effects on N and water availability to subsequent no‐till corn (Zea mays L.) have not been studied. This 2‐yr study was conducted in 1990 and 1991 at Coastal Plain and Piedmont locations in Maryland to evaluate soil moisture and corn responses to three cover crop kill dates, three corn planting dates, and four fertilizer N (FN) rates following cover crops of hairy vetch (Vicia villosa Roth), cereal rye (Secale cereale L.), and vetch‐rye mixture. No‐cover checks were included for each corn planting date. Corn yield ranged from 0.8 to 13.3 Mg ha−1 in 1990, and from 3.9 to 12.6 Mg ha−1 in 1991. Corn grain yield without FN was greatest following vetch or vetch‐rye mixture. Late April or early May kill dates consistently resulted in greater corn yield than earlier kill dates, probably due to differences in N availability and moisture conservation. Cover crops killed late did not deplete surface soil moisture. The economic FN rate reflected N contributions and moisture conservation by each cover crop. At the Coastal Plain location, economic FN rates were 30 to 76 kg ha−1 for corn following vetch, 65 to 193 kg ha−1 following vetch‐rye mixture, 161 to 247 kg ha−1 following rye, and 201 kg ha−1 following no cover crop. Similar rankings were observed for the Piedmont location, but maximum yield was lower following rye, and lower FN rates were required to attain that yield. Summer soil water conservation by cover crop residues was more important than spring moisture depletion by growing cover crops in determining final corn yield.
Turfgrass Response to Slow‐Release Nitrogen Fertilizers
Authors: Carrow Robert N.
Published: July 2010

New polymer coatings have been developed and used to coat sulfurcoated urea (SCU) and other core N materials. These polymer‐coated S‐coated ureas (PCSCU) and polymer‐coated S‐coated N‐P‐K fertilizers (PCSCF) require evaluation for their N‐release properties turfgrass culture. Also, N carriers from three different classes of N sources were included: polymer‐coated urea (PCU), ureaformaldehyde (UF) reaction products, and natural organics. Initial and longterm N release were determined as demonstrated by visual quality, total shoot growth, and number of mowings of ‘Tifway’ hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davey] grown on an Appling sandy clay loam (clayey, kaolinitic, thermic Typic Kanhapludults). All N carriers were compared within their N class and across all carriers, using urea applied at 98 kg N ha−1 in early summer of 1994 and 1995 as the base of comparison. Other fertilizers were also applied at this rate and timing, except for three urea‐UF reaction products applied in equal, split treatments in early and mid summer. At 0 to 30 d of treatment, PCSCU and PCSCF product performance varied, with 14 to 57% of visual quality ratings equal to or greater than (≥) urea plots; at 61 to 95 d, 14 to 57% of ratings were > urea ratings. Greater long‐term quality response was related to higher S and/or polymer content in the coating of PCSCU and PCU products, but not to larger particle size for PCSCUs. For PCUs, the 0‐ to 30‐d visual quality response ranged from 14 to 43% of ratings ≥ urea, and at 61 to 95 d from 29 to 71% of ratings > urea. Natural organics and UF reaction products also demonstrated wide variation within their class of initial and long‐term N release. Within each N class, the wide diversity of N‐release patterns indicates the need to evaluate each carrier, and shows that placement of a specific N source within an N class provides only very broad implications as to its performance.
Suppression of Junglerice [Echinochloa colona (L.) Link] by Irrigated Rice Cultivars in Latin America
Authors: Fischer Albert , Ramírez Hector V. , Lozano Jaime
Published: July 2010

Continuous rice (Oryza sativa L.) cropping in Latin America and the Caribbean has resulted in serious weed problems and herbicide overuse. Competitive rice cultivars could help reduce herbicide dependence. A study was conducted during 1994 and 1995 at Palmira, Colombia, to (i) assess the competitiveness of semidwarf irrigated rice plant types adapted to Latin America and the Caribbean's direct‐seeding systems, (ii) identify plant traits responsible for such competitiveness, and (iii) detect adverse effects of competitiveness on rice yield potential. Pregerminated seed of 10 and 14 semidwarf rice cultivars was sown on drained puddled soil in 1994 and 1995, respectively. Cultivars were grown weed‐free or with junglerice [Echinochloa colona (L.) Link] (40 viable seeds m−2, broadcast immediately after seeding rice), and were intermittently irrigated to keep the soil near saturation. Rice and junglerice biomass, leaf area index, tiller number, and height were recorded at 20, 40, 60, 90, and 120 days after emergence (DAE). Rice cultivars differed in their competitiveness against junglerice. Average yield losses ranged from 27 to 62% under saturating junglerice infestations of up to 5.9 Mg DM ha−1. Leaf area index, tiller number, and canopy light interception recorded in competition, and not much before 40 DAE, correlated positively with rice competitiveness. Competitive semidwarf cultivars can substantially reduce the number of herbicide applications in systems where suboptimal water control does not allow weed suppression by flooding. Breeding to enhance rice competitiveness appears as a valid objective, since competitive and also highly productive cultivars were identified in this study.
Residue and Fertility Effects on Yield of No‐Till Wheat
Authors: Rasmussen Paul E. , Rickman Ron W. , Kleeper Betty L.
Published: July 2010

High levels of crop residue can adversely affect wheat (Triticum aestivum L.) yield, thereby slowing adoption of conservation tillage practices that effectively control soil erosion. This study was conducted to determine the influence of standing wheat residue and fertilizer application on the yield of no‐till wheat. Winter wheat was grown in even years and spring wheat in odd years on the same site from 1984 through 1988. The soil (a Walla Walla silt loam; coarse silty, mixed mesic Typic Haploxeroll) is considered highly deficient in N and marginally deficient in P and S for annual cereal production. Crop residue was finely chopped in 1984 and burned in 1985 to 1988, to compare with stubble left standing. Fertility treatments consisted of increasing rates of N, P, and S [none (0–0–0 kg N–P–S ha−1), low (56–6–9), moderate (112–11–18), and high (168–17–27)], banded cm below the seed. Grain yield, straw yield, grain protein, head density, kernels per head, and kernel weight were determined at harvest. Standing stubble decreased grain yield of winter wheat 13% and straw yield 15%, compared with chopping or burning; it decreased spring wheat grain and straw yields <5%. Standing residue affected straw and grain yields similarly, but had little effect on grain protein. Fertilizer increased grain and straw yield every year, and more so in winter than in spring wheat. Average grain yields for none, low, moderate, and high fertility were 1.12, 3.02, 4.75, and 5.08 t ha−1, respectively, for winter wheat and 1.17, 2.64, 3.18, and 3.20 t ha−1 for spring wheat. Increasing fertilization increased head numbers, had variable effect on head size, and generally decreased kernel weight. Most of the yield reduction in winter wheat due to standing residue was attributed to lower head numbers, not compensated by increased head size or kernel weight. Fertility × residue interaction did not occur in yield or grain protein responses, but was found in kernel yield and kernel weight. Lack of such interaction suggests that inadequate nutrition was not the cause of reduced yield in no‐till wheat with residue left standing.
Agronomic and Economic Evaluation of Organic and Inorganic Sources of Phosphorus in Western Kenya
Authors: Jama Bashir , Swinkels Rob A. , Buresh Roland J.
Published: July 2010

Many soils in the highlands of East and Central Africa are depleted of soil nutrients, particularly P. Our objective was to compare cattle manure, Calliandra calothyrsus Meissner leaf biomass, and triple superphosphate (TSP) as sources of P for maize (Zea mays L.), both individually and as mixtures of organic (manure or calliandra) and inorganic (TSP + urea) sources. Field experiments were conducted on a Kandiudalf at two sites in western Kenya. Net benefits were computed as the difference between the value of additional maize yield accruing from nutrient inputs and the associated additional costs. Maize grain yield was 0.6 Mg ha−1 for application of urea without P. Application of 10 kg P ha−1 as organic, inorganic, and mixtures of organic and inorganic sources significantly increased maize yield. Grain yield for manure at least equaled and sometimes exceeded (P ≤ 0.05) yield for calliandra and TSP + urea. Net benefits in U.S. dollars (USD) for two seasons were highest for manure spot placed in the planting hole (293 USD ha−1), broadcast manure (255 USD ha−1), and broadcast TSP + 44 kg urea‐N ha−1 (313 USD ha−1 at P = 30 kg ha−1 and 98 USD ha−1 at P = 10 kg ha−1). Net benefits for calliandra leaf biomass were highest (136 USD ha−1) when biomass was valued at cost of production and integrated with TSP, such that it provided all the N for maize and TSP provided the additional P not supplied by calliandra. Calliandra valued at its opportunity cost as a protein supplement for dairy cattle was not an economic source of P. Sensitivity analyses suggest that organic materials most suitable for use as P sources have high P content and low cost of production.
Corn Growth and Nitrogen Uptake with Furrow Irrigation and Fertilizer Bands
Authors: Benjamin Joseph G. , Porter Lynn K. , Duke Harold R. , Ahuja Lajpat R.
Published: July 2010

Furrow irrigation is commonly used to provide supplemental water to row crops. Alternate‐furrow irrigation has been proposed as a method to decrease deep percolation water losses as well as the leaching of fertilizer and pesticides. A study was conducted on a Ulm clay loam (fine, smectitic, mesic Ustic Haplargids) in 1994 and 1995 near Fort Collins, CO. Corn (Zea mays L.) growth and N uptake were measured under alternate‐furrow and every‐furrow irrigation water applications, each with fertilizer bands placed either in the row or in the furrow. Nitrogen‐15‐depleted (NH4)2SO4 fertilizer was used to distinguish plant uptake of fertilizer N from uptake of naturally occurring N. There were no differences in plant response to alternate‐furrow or every‐furrow irrigation water placement for the same amount of water applied. Greater fertilizer‐N uptake occurred with row placement than with furrow placement of N fertilizer. Early in the growing season, fertilizer‐N uptake from row placement was from 2 to 10 times the fertilizer‐N uptake from furrow placement. By the end of the growing season, the average total‐N uptake from row placement was 12% greater than for furrow placement. Placing the fertilizer in the nonirrigated furrow of the alternate‐furrow irrigation treatment decreased N availability by 20% compared with the average of the other treatments. If alternate‐furrow irrigation is used to increase water use efficiency in furrow‐irrigated fields, placing the N fertilizer in the nonirrigated furrow of the alternate‐furrow irrigation system could decrease N availability because of drier soil conditions in the nonirrigated furrow. Row placement of N fertilizer seems to be beneficial in both alternate‐furrow and every‐furrow irrigation applications.