bluuebunny/crossref_metadata_2025 huggingface dataset:
Winter Rye Cover Crop Following Soybean Under Conservation Tillage: Residual Soil Nitrate
Authors: Kessavalou Anabayan , Walters Daniel T.
Published: July 2010

Use of a winter rye (Secale cereale L.) cover crop following soybean [Glycine max (L.) Merr.] has been shown to reduce the soil erosion potential in a corn (Zea mays L.)–soybean rotation system, but little is known about the effect of rye on residual soil NO3–N (RSN). An irrigated field study was conducted for 4 yr on a Sharpsburg silty clay loam (fine, smectitic, mesic Typic Argiudoll) to compare crop rotation and winter rye cover crop following soybean effects on RSN under several tillage practices and N fertilization rates. Treatments each year were (i) tillage: no‐till or disk; (ii) rotation: corn following soybean/rye (Cbr) or soybean/rye following corn (BRc), corn following soybean (Cb) or soybean following corn (Bc), and corn following corn (Cc); and (iii) N rate: 0, 100, and 300 kg N ha−1 (applied to corn). Rye in the Cbr/BRc rotation was planted in the fall following soybean harvest and chemically killed in the spring of the following year prior to corn planting. Each spring, before tillage and N application, RSN was determined to a depth of 1.5 m, at 30‐cm intervals. The net spring‐to‐spring change in RSN between subsequent spring seasons was computed for each plot, and annual aboveground N uptake for rye, corn, and soybean were determined. Rye, rotation, N rate, and tillage significantly influenced RSN in the top 1.5 m of soil. The presence of rye (BRc) reduced total spring RSN between 18 and 33% prior to corn planting in 2 of the 3 yr, compared with the no‐rye system (Bc), as rye immobilized from 42 to 48 kg N ha−1 in aboveground dry matter. Recycling of N in high‐yielding rye cover crop residues led to an increase in RSN accumulation after corn in the succeeding spring. Up to 277 kg RSN ha−1 accumulated at high rates of N following corn in the Cbr rotation, compared with 67 kg RSN ha−1 in the no‐rye system (Cb) in 1992. Regardless of the presence of rye, significant accumulation of RSN occurred following corn in the rotation sequence, while RSN declined following soybean. Less RSN was found in the top 1.5 m of soil under continuous than rotation corn, and disking tended to increase NO−3 accumulation in rotation systems at high rates of N application. Although RSN declines following a rye cover crop, the ready release of this immobilized N suggests that some N credit should be given, reducing N recommendation for corn following winter rye cover, to minimize potential NO−3 leaching under corn–soybean/rye rotations.
Soil Nitrogen Amendment Effects on Nitrogen Uptake and Grain Yield of Maize
Authors: Ma B. L. , Dwyer Lianne M. , Gregorich Edward G.
Published: July 2010

Efficient use of soil N amendments in maize (Zea maysL.) production is necessary to maximize producer's economic returns and to maintain soil and water quality. A 5‐year field experiment was conducted on a Brandon loam soil (fine loamy, mixed, mesic Typic Endoaquoll) (Orthic Humic Gleysol) with the objective of measuring N uptake and grain yield of two maize hybrids under different N amendments [no amendment, NH4NO3at 100 and 200 kg N ha−1, and stockpiled and rotted dairy manure at 50 and 100 Mg ha−1(wet wt.)] to determine differences in N use efficiency (NUE) and its components, N uptake efficiency and N utilization efficiency. The N amendments increased the grain yield (by an average of 20%) and NUE (by an average of 17.5%) of a modern hybrid (Pioneer ‘3902’) more than that of an old hybrid (‘Pride 5’). The difference method that was used to estimate N recovery indicated that, over the course of the study, Pioneer 3902 took up 48% of inorganic fertilizer N and 20% of the manure N, compared with 42 and 16%, respectively, for Pride 5. Manure application resulted in total N uptake comparable to the 200 kg N ha−1treatment. Grain yields of manure treatments in 1993 and 1994 were generally lower (5–15%) than the 200 kg N ha−1treatment. During the latter periods (1995 and 1996) of the study with repeated application under continuous maize, all manure treatments produced grain yields equal to or slightly greater (6–13%) than the fertilizer treatment. Dairy manure application increased N uptake and grain yield of maize. The NUE, based on added mineral N levels, for all manure treatments was greater than for the 200 kg N ha−1treatment.
Response of Selected and Unselected Bahiagrass Populations to Defoliation
Authors: Gates Roger N. , Hill Gary M. , Burton Glenn W.
Published: July 2010

Recurrent restricted phenotypic selection (RRPS) has increased spaced‐plant yield of ‘Pensacola’ bahiagrass (Paspalum notatum Flügge var. saurae Parodi) and led to higher‐yielding, more erect genotypes. Response to defoliation was examined in three entries: selection Cycle 0, Pensacola; Cycle 9, ‘Tifton 9’, and Cycle 14. In a 3‐yr plot study, two cutting heights (15 or 100 mm) in combination with three regrowth intervals (2, 4, or 8 wk) were imposed throughout 24 wk. A split‐split plot arrangement of regrowth interval (whole plot), cutting height (subplot) and entry (sub‐subplot) was used, with six replications. In a 2‐yr grazing study, response of the same entries to defoliation from continuous stocking was evaluated. In the plot study, yield (7030 kg ha−1) was maximized by low cutting height and 8‐wk regrowth interval during the first year. In Year 2, a 4‐wk regrowth interval and low cutting height produced the highest yield (11220 kg ha−1). Mean yields of Tifton 9 (7650 kg ha−1) and RRPS cycle 14 (7320 kg ha−1) were greater than Pensacola (6500 kg ha−1), but response of entries to cutting height and regrowth interval varied among years. In the grazing study, herbage mass was greater for Tifton 9 (1670 kg ha−1) and RRPS Cycle 14 (2000 kg ha−1) than for Pensacola (1420 kg ha−1). Carrying capacity of Tifton 9 (935 d ha−1) was greater than Pensacola (855 d ha−1). Daily gains were similar (0.34 kg) for all germplasms. Bahiagrass stand declined rapidly for RRPS Cycle 14. Continuous stocking at high grazing pressure was not suitable for RRPS Cycle 14.
Productivity and Nutritive Value of ‘Florakirk’ Bermudagrass as Affected by Grazing Management
Authors: Pedreira Carlos G. S. , Sollenberger Lynn E. , Mislevy Paul
Published: July 2010

‘Florakirk’ bermudagrass [Cynodon dactylon (L.) Pers.] is a recently released cultivar for the lower southeastern USA, but its evaluation under grazing has been limited to southern Florida. Herbage accumulation, crude protein (CP), and in vitro digestible organic matter (IVDOM) responses of Florakirk to grazing management were studied in 1993 and 1994 on a sandy, siliceous, hyperthermic Ultic Haplaquod in northern Florida. Treatments were replicated twice in a randomized block design and consisted of all combinations of three lengths of grazing cycle (GC) (7, 21, and 35 d) and three postgraze stubble heights (SH) (8, 16, and 24 cm). Actual grazing periods were from 1 to 12 h. Herbage accumulation ranged from 6.9 to 17 Mg ha−1 and was maximized when pastures were grazed to a 24‐cm SH every 7 d in 1993, and to 24 cm every 35 d in 1994. Lowest herbage accumulation occurred when pastures were grazed to an 8‐cm SH every 21 d. Treatment combinations involving GC 7 were associated with high herbage accumulation in both years of the study. Nutritive value varied relatively little across the range of treatments imposed. Crude protein concentration ranged from 96 to 113 g kg−1 in 1993 and from 121 to 134 g kg−1 in 1994. Lower CP was associated with longer GCs in both years. In vitro digestible organic matter concentration was greatest at short SHs for all but the shortest GCs in 1993 and was greatest at intermediate GCs in 1994. Florakirk herbage accumulation was affected primarily by SH, and nutritive value was affected primarily by GC. Grazing to a SH of approximately 20 cm every 14 d is predicted by regression models to result in near maximum levels of both herbage accumulation and nutritive value.
Soil Nitrogen Amendment Effects on Seasonal Nitrogen Mineralization and Nitrogen Cycling in Maize Production
Authors: Ma B. L. , Dwyer Lianne M. , Gregorich Edward G.
Published: July 2010

Nitrogen use efficiency (NUE) is a measure of the extent to which a crop transforms available N to economic yield. Seasonal N mineralization of organic amendments increases available N and, depending on the timing of mineralization and crop requirements for N, may improve NUE while reducing soil N losses. A two‐year study was conducted in an ongoing five‐year field experiment (1992–1996) on a Brandon loam soil (fine‐loamy, mixed, mesic Typic Endoaquoll) (Orthic Humic Gleysol) at the Central Experimental Farm, Ottawa, ON, Canada (45°23′ N, 75°43′ W). Our objectives were to (i) quantify the effects of inorganic N fertilizer, stockpiled (SM), and rotted manure (RM) application on seasonal N mineralization and (ii) monitor the mineral N balance in the soil–plant system. Application of manure at the highest rate having a mineral N (NH+4plus NO−3) of ≈100 kg N ha−1and up to 800 kg N ha−1of total N resulted in up to 120 kg ha−1of net N mineralized. The potential loss of this mineralized N was minimized during the growing season compared with inorganic fertilizer application because of the synchronization of soil N release and uptake by maize (Zea maysL.). In soil receiving 200 kg inorganic N ha−1, the amount of net N mineralized over the season was between 130 and 170 kg ha−1, but large losses of mineral N from the rooting zone occurred during the same period. The amount of net N mineralized over the season accounted for up to half of the plant N uptake in all treatments; for example, the amount of net N mineralized in manured soils represented about 30 to 60% of total plant N. It appears that a priming effect on soil mineral N occurred in all treatments during the vegetative period. This resulted in a curvilinear relationship between net N mineralization rate and soil mineral N levels at pre‐planting that reached a plateau at ≈140 kg N ha−1. The rate of N mineralization during the grain‐filling period was approximately the same at both levels of inorganic N fertilizer, but was, on average, three times higher under manure treatments. Compared with N mineralization under the 200 kg N ha−1fertilizer treatment, all manure treatments resulted in higher rates of net N mineralization during the grain‐filling period.
Cover Crops and Nutrient Retention for Subsequent Sweet Corn Production
Authors: Isse A. A. , MacKenzie Angus F. , Stewart Katrine , Cloutier Daniel C. , Smith Donald L.
Published: July 2010

The use of high rates of N fertilizer in intensive sweet corn (Zea maysL.) production may result in leaching losses and contamination of adjacent waterways and ground water. Cover crops planted after sweet corn harvest could absorb residual soil N and minimize losses of fertilizer in gravitational water. Field experiments were conducted on a Ste. Rosalie heavy clay (fine, mixed, frigid, Typic Humaquept) and a St. Bernard sandy clay loam (fine loamy, mixed, nonacid, frigid Typic Eutrochrept). Cover crop effects on nutrient uptake, subsequent N release, loss of N, P, and K in leaching water, and denitrification rates were measured. Fertilizer N rates were 0, 75, and 150 kg ha−1Cover crops were red clover (Trifolium pratenseL.), crimson clover (Trifolium incarnatumL.), forage radish (Raphanus sativusL.), canola (Brassica rapaL.), barley (Hordeum vulgareL.), and annual ryegrass (Lolium multiflorumL.). A control treatment with no cover crop was also included. Three replicates were used in a split‐plot arrangement of a randomized complete block design. Fall residual soil NO−3–N levels were higher in control plots than cover crop plots. Gravitational water NO−3–N was greater in control plots and ranged from 17 to 76 kg N yr−1N, compared with cover crop plot values of 1 to 55 kg N yr−1. Cover crops had no effect on denitrification rates, or on NH+4–N, P, or K concentrations in gravitational water. Forage radish, canola, and barley were effective cover crops in reducing soil NO−3–N. Cover crop effects on subsequent sweet corn were found only in grain N uptake.
Spring Wheat Response to Tillage System and Nitrogen Fertilization within a Crop–Fallow System
Authors: Halvorson Ardell D. , Black Alfred L. , Krupinsky Joseph M. , Merrill Steven D. , Wienhold Brian J. , Tanaka Donald L.
Published: July 2010

Spring wheat (Triticum aestivum L.) production in the northern Great Plains generally utilizes conventional tillage systems. A 12‐yr study evaluated the effects of tillage system [conventional‐till (CT), minimum‐till (MT), and no‐till (NT)], N fertilizer rate (0, 22, and 45 kg N ha−1), and cultivar (Butte86 and Stoa) on spring wheat grain yields in a dryland spring wheat–fallow rotation (SW–F). Butte86 yields with CT exceeded NT yields in five out of 12 years with 0 and 22 kg N ha−1 applied, and four years with 45 kg N ha−1 applied. Stoa yields with CT exceeded NT yields in three out of 12 years with no N applied, four years with 22 kg N ha−1 applied, and only one year with 45 kg N ha−1 applied. Yields with NT exceeded those with CT in one year. Most years, yields with MT equaled those with CT. Responses to N tended to be greatest in years when spring soil NO3–N was lowest. Positive yield responses to N fertilization with CT occurred in three years with Butte86 and two years with Stoa; with MT, four years with Butte86 and two years with Stoa; and with NT, five years with Butte86 and three years with Stoa. Cultivars were not consistent in their response to tillage and N fertilization. These results indicate that farmers in the northern Great Plains can successfully produce spring wheat in a SW–F system using MT and NT systems, but yields may be slightly reduced when compared with CT systems some years.
Preplant Slow‐Release Nitrogen Fertilizers Produce Similar Bell Pepper Yields as Split Applications of Soluble Fertilizer
Authors: Guertal Elizabeth A.
Published: July 2010

Slow‐release N materials are used to reduce N leaching losses from sandy soils and extend N availability over a growing season. The objective of this research was to examine the effectiveness of preplant sulfur‐coated urea (SCU) and polyolefin resin‐coated urea (PCU) N fertilizers compared to split applications of soluble fertilizer on green bell pepper (Capsicum annuumL.) yield and quality. The 3‐yr experiment consisted of green bell peppers grown on 15‐cm raised beds utilizing plastic mulch and drip irrigation. Treatments were N source (preplant SCU, preplant PCU, and fertigated ammonium nitrate) and N rate (90, 135, 180, or 225 kg N ha−1). Ammonium nitrate (AN) was applied as a split application, with 20% preplant and 80% applied every‐other week in five equal applications. Other N sources were applied 100% preplant. A zero N control was also included. Collected data included plant height, leaf N content, and fruit yield and quality. In two of three years pepper yield was maximized at or near the Alabama recommended rate of 135 kg N ha−1. Nitrogen source rarely affected the partitioning of harvested peppers into grade groups. Adding N from any N source decreased percent nonmarketable yield (cull) and increased the percentage of marketable yield that was large (U.S. 1) peppers. There were few consistent differences in pepper yield or quality due to N source. Given cost considerations of drip application and N sources, slow‐release N materials may be a viable option for small‐scale growers not using drip application systems.
Reversal of Rice Yield Decline in a Long‐Term Continuous Cropping Experiment
Authors: Dobermann Achim , Dawe David , Roetter Reimund P. , Cassman Kenneth G.
Published: July 2010

In a long‐term continuous cropping experiment at Los Baños, Philippines, three rice (Oryza sativaL.) crops were grown each year with the goals of maximum annual grain production and high N use efficiency. Our objective was to identify the factors responsible for the restoration of yields occurring after 1991. From 1968 to 1991, grain yields declined at an annual rate of 1.4 to 2.0%. From 1991 to 1995, dry season (DS) yields in the highest N treatment increased to within 80 to 100% of the simulated yield potential; yields in the unfertilized control did not increase. Increased solar radiation, increased N rate, and improved timing of N applications accounted for the restoration of yields in the DS. Wet season yields increased in fertilized and unfertilized plots due to greater solar radiation, improved timing of N applications, and increased soil N supply due to dry fallow periods in three years. Residual benefits of soil aeration were short‐term. Reducing preplant N fertilizer and increasing the number of split applications had a greater effect on increasing yield than the increase in the amount of N applied. Our results provide evidence that N deficiency caused the yield decline before 1991. However, the actual processes that caused a decline in soil N supply or plant N uptake remain to be determined. It is possible to sustain high yields and high N use efficiency if fertilizer regimes are updated regularly to maintain the congruence between crop N demand and the N supply from soil and fertilizer.
Corn Production with Kura Clover as a Living Mulch
Authors: Zemenchik Robert A. , Albrecht Kenneth A. , Boerboom Chris M. , Lauer Joseph G.
Published: July 2010

Cropping systems that improve soil conservation are needed for mixed grain and forage enterprises in the upper Midwest. Our objective was to determine whether established kura clover (Trifolium ambiguumM. Bieb.) stands could serve as a living mulch for no‐till corn (Zea maysL.) production, followed by a return to clover without replanting. Treatments included corn sown into established kura clover that was: (1) killed and sidedressed with N, (2) killed, (3) band‐killed, leaving 15 cm of untreated kura clover between rows, (4) suppressed and sidedressed with N, and (5) suppressed and (6) untreated kura clover without corn. Corn whole‐plant yield in 1996 ranged from 14.0 to 15.7 Mg ha−1and was greatest in Treatments 2 and 4 and least in Treatment 5. Corn whole‐plant yield in 1997 ranged from 9.5 to16.9 Mg ha−1and was greatest in Treatments 1 and 2 and least in Treatment 5. Grain yields in 1996 were not different among treatments, while in 1997 yields ranged from 7.2 to 11.1 Mg ha−1and were greatest in Treatments 1 and 2 and least in Treatment 5. Clover yield in 1997 following 1996 corn production was greatest in the untreated control, but there was no clover yield difference in 1998 following either 1996 or 1997 corn production. Kura clover can be managed as a living mulch in corn with little or no corn whole‐plant or grain yield reduction and clover will recover to full production within 12 mo without replanting.
Agronomic Changes from 58 Years of Genetic Improvement of Short‐Season Soybean Cultivars in Canada
Authors: Morrison Malcolm J. , Voldeng Harvey D. , Cober Elroy R.
Published: July 2010

Yield progress of short‐season soybean [Glycine max (L.) Merr.] cultivars in Canada has been approximately 0.5% per year since the early 1930s. Our objective was to identify changes in agronomic traits associated with yield increase within a selection of historical cultivars. Where applicable, we measured phenotypic stability of these traits. At Ottawa, ON, we grew 14 cultivars, representing seven decades of breeding and selection (1934–1992), in a randomized complete block design with four replicates, across 6 yr. Data were collected on seed yield, seed weight, plant height, plant population, lodging susceptibility, and foliar disease symptoms. Seed number per plant was calculated from yield, seed weight, and plant population. Seed protein and oil concentration were measured. The increase in seed yield with year of release was associated with a significant increase in the number of seeds produced per plant. There was no relationship between seed yield and seed weight. A significant decrease in seed protein concentration with year of release was offset by a significant increase in seed oil concentration. Newer cultivars were more phenotypically stable for plant height than older cultivars. Modern cultivars were more efficient at establishing, supporting, and filling seeds on a per‐plant basis than older cultivars.
Tillage, Cover Cropping, and Poultry Litter Effects on Cotton: II. Growth and Yield Parameters
Authors: Nyakatawa Ermson Z. , Reddy K.Chandra , Mays David A.
Published: July 2010

The development of conservation tillage systems for cotton (Gossypium hirsutumL.), capable of reducing soil erosion and improving soil quality while increasing yields and profits, remains a challenge in the southeastern USA. Poor emergence and growth, delayed maturity, and reduced yield are some of the problems that have been encountered in the use of conservation tillage on cotton. The objectives of this study was to evaluate the effects of tillage (no‐till, mulch‐till, conventional till), cropping system [cotton–winter fallow, cotton–winter rye (Secale cerealeL.) cover crop] and N source (poultry litter, ammonium nitrate) on growth and yield of cotton from 1996 to 1998 in northern Alabama. In 1997, cotton lint yield under no‐till (NT) was 24 and 18% greater than that under conventional till (CT) and mulch‐till (MT) systems, respectively. In 1998, cotton lint yield under the NT system was 7% greater than that under CT. Poultry litter (PL) at 100 kg N ha−1gave similar lint yield to ammonium nitrate (AN), whereas at 200 kg N ha−1, lint yields were significantly greater. No‐till, cotton–winter rye cropping, and surface application of 200 kg N ha−1in form of PL conserved soil moisture in the top 7 cm of the soil. This resulted in early seedling emergence, high seedling vigor, good plant growth, and high lint yield of cotton. These treatments would be appropriate for use in the southeastern USA where soil erosion is a problem and plenty of PL is available each year from the poultry industry.
Timing and Frequency of Between‐Row Mowing and Band‐Applied Herbicide for Annual Weed Control in Soybean
Authors: Donald William W.
Published: July 2010

Alternative ways are needed to control weeds in field crops that reduce or prevent both herbicide contamination of surface and ground water and soil erosion. A new weed management system, which consisted of band‐applied herbicides over the soybean [Glycine max (L.) Merr., ‘Morsoy 9137’] row and two or more between‐row (BR) mowings, was optimized in a soybean field near Columbia, MO. Between‐row mowing very close to the soil surface twice with a mower killed or suppressed annual grass and broadleaf weeds, chiefly giant foxtail (Setaria faberi R. Herrm.), common ragweed (Ambrosia artemisiifolia L.), and waterhemp species (Amaranthus spp.), when properly timed. When band‐applied herbicide controlled weeds within the crop row, annual weeds between rows could be mowed once when the tallest weeds were 8 to 24 cm tall and again just before crop canopy closure, without yield loss. No more than two BR mowings were needed to control annual weeds. Shading by crop canopy closure contributed to weed suppression in this BR‐mowing weed management system. Soybean yield in the BR‐mowing weed management system could not be statistically distinguished from hoed, weed‐free check plots or broadcast‐herbicide treatments and was greater than the weedy check plots. Herbicide use was reduced 50% by banding because only 50% of the field area was sprayed. The BR‐mowing weed management system may have use in environmentally sensitive areas to help reduce soil erosion and/or water contamination by herbicides.
Mixture of Time Scales in Evaporation: Desorption and Self‐Similarity of Energy Fluxes
Authors: Porté‐Agel Fernando , Parlange Marc B. , Cahill Anthony T. , Gruber Alexander
Published: July 2010

The time evolution of evaporation from a bare soil, over a 9‐d period following irrigation, is described by a combination of daily and hourly drying patterns. From the second day, the daily evaporation shows a second stage of drying that can be described as a desorptive process (evaporation proportional to (t − to)−1/2, where t is time in days and to is the day when the second stage starts). The short time (hourly) evaporation rate can be modeled on the basis of a type of self‐similarity in the energy balance components. Combining the evaporative flux behavior at the two time scales, desorption at the daily timescale and self‐similarity for the diurnal variations, a robust description of evaporation for drying land surfaces is obtained. This approach is tested using accurate measurements of the different components of the energy balance at the soil surface, obtained at 20‐min intervals. The model accurately describes the time evolution of the evaporative flux and could be used for the disaggregation of daily or weekly evaporation into hourly values.
Swine Manure Application to Nodulating and Nonnodulating Soybean
Authors: Schmidt John P. , Schmitt Michael A. , Randall Gyles W. , Lamb John A. , Orf James H. , Gollany Hero T.
Published: July 2010

Manure has traditionally been applied to corn (Zea maysL.), but as livestock operations expand, there are not always sufficient corn acres to minimize the environmental impact of the manure load. Our objective was to evaluate soybean [Glycine max(L.) Merr.] as a reasonable alternative crop to receive manure applications. Impact of manure applications on soybean was measured by evaluating seed yield, N accumulation, and soil NO3–N at six locations in southern Minnesota in 1996 and 1997. Whole‐plot treatments included a control, five liquid swine (Sus scrofa) manure rates (100, 200, 300, 400, and 500 kg N ha−1), and four NH4NO3rates (84, 168, 252, and 336 kg N ha−1). Split‐plot treatments were two soybean isolines (a segregating row of an Altona × Chippewa withrj1gene cross), one nodulating and one nonnodulating isoline. Maximum seed yield (2.3 Mg ha−1) was obtained for the nodulating isoline regardless of manure or fertilizer treatment. Average N accumulation in the nodulating isoline with manure treatment was about 202 kg N ha−1. This was about 11 kg N ha−1greater than the nodulating isoline with fertilizer treatment. There were no adverse agronomic effects of applying manure to soybean. At N applications greater than plant N accumulation, postharvest soil NO3–N (0–120 cm) ranged from 80 to 158 kg N ha−1. Manure applied to soybean at available N rates equal to or less than the amount of N accumulated in the crop appeared to be agronomically and environmentally sound.
Maize Response to Time of Nitrogen Application as Affected by Level of Nitrogen Deficiency
Authors: Binder Darren L. , Sander Donald H. , Walters Daniel T.
Published: July 2010

Fine tuning current best nitrogen management practices, such as delayed N application to maize (Zea mays L.), is needed to improve fertilizer recommendations. This study was conducted to determine the relationship between relative maize N deficiency and time of N application. Levels of N deficiency were established by applying different rates of N fertilizer. Additional N was applied to each level of N deficiency at eight growth stages ranging from early vegetative growth to late reproductive growth. Chlorophyll meter readings were taken before each N application as a measure of maize N deficiency. A N sufficiency index (SI) was calculated based on the relationship between N‐deficient and non‐N‐deficient maize. Delaying N application to the six‐leaf stage resulted in nearly a 12% decrease from maximum grain yield when the SI was below 0.90, indicating N deficiency can be severe enough to prevent full recovery when N is side dressed. The greater the N deficiency, the earlier N had to be applied to obtain maximum grain production. Grain yield was increased from N application as late as R3 stage for extremely N‐deficient maize, but maximum yield was not obtained. Grain yield was depressed when N was applied at R3 for slightly N‐deficient maize. The potential benefit of late season N application depends on the degree of N deficiency. A predictive function was developed in order to determine if N fertilizer application would be warranted given the SI and time of N application.
Relationships between Biomass and Phenolic Production in Grain Sorghum Grown under Different Conditions
Authors: Sène Maniével , Doré Thierry , Gallet Christiane
Published: July 2010

The total phenol pool (kg ha−1) of the aerial parts and roots of sorghum (Sorghum bicolorL. cv. CE145−66) crops and their relationships to dry matter and total phenol concentrations (g kg−1) were studied in four different data sets (2 sites × 2 yr for a total of 52 smallholder fields) in Senegal. The total phenol pool size varied from 4 to 156 kg ha−1in the aerial parts and from 1 to 16 kg ha−1in the roots. The phenol pool size was closely correlated with the amount of dry matter in both the aerial parts (r= 0.95,P<0.001) and the roots (r= 0.91,P<0.001). In contrast, the phenol concentrations varied less between fields than the dry matter content, and therefore had less impact on the phenol pool size. Using a N nutrition index (NNI) to assess the N nutrition of the sorghum crops, both phenol the pool and concentration were higher when N nutrition was better. Grain yield and the phenol pool of aerial parts were also positively correlated. The data indicate that the environmental factors that promote growth and grain yield also enhance the total phenol synthesis in sorghum vegetative parts.
Rust‐Enhanced Allelopathy of Perennial Ryegrass against White Clover
Authors: Mattner Scott W. , Parbery Douglas G.
Published: July 2010

Perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) are important pasture components in the higher rainfall areas of southeastern Australia. Crown rust (Puccinia coronata Corda f.sp. lolii Brown) is the most serious ryegrass pathogen in these areas. In a preliminary investigation, rust reduced ryegrass biomass by 56%. Yet, interference from rusted ryegrass suppressed the yield of neighboring clover plants more than interference from healthy ryegrass. The role of allelopathy in this relationship was investigated in a greenhouse study using two bioassays. Soil previously growing rusted ryegrass suppressed clover biomass by 36% compared with soil previously growing healthy ryegrass. Similarly, leachate from soil surrounding rusted ryegrass suppressed clover biomass by 27% compared with that from healthy ryegrass. This is the first demonstration that a pathogen may influence allelopathy between plants and that rust may enhance ryegrass allelopathy against clover. Possible implications of this in pasture ecology and the evolution of mutualism are discussed.
Grass and Legume Cover Crop Effects on Dry Matter and Nitrogen Accumulation
Authors: Odhiambo Jude J. O. , Bomke Arthur A.
Published: July 2010

Careful cover crop management during the spring growth period may allow farmers to maximize dry matter (DM) yield and N accumulation for the subsequent crop. A 2‐yr study was conducted to determine the effect of grass and legume cover crops on spring DM production and N accumulation. Each year, cover crops were planted in late August and late September on a loamy, mixed, mesic Humaquept in the Fraser River Delta. Wheat (Triticum aestivumL.), rye (Secale cerealeL.), and ryegrass (Lolium multiflorumL.) were planted in monoculture and in mixtures with crimson clover (Trifolium incarnatumL.). Other treatments included pure stand of crimson clover and wheat–hairy vetch (Vicia villosaRoth.) mixture. Cover crop biomass was sampled three times in 1995 and four times in 1996 during the spring growth period. Dry matter accumulation of early planted cover crops increased by 26 to 269% during the spring growth period, ranging between 0.6 Mg ha−1for clover and 10 Mg ha−1for wheat, wheat–clover, and wheat–vetch treatments. Late‐planted cover crops produced between 15 and 75% lower DM yield compared with early planted cover crops. Nitrogen accumulation increased by 3 to 74 kg ha−1for early planted crops and by 3 to 47 kg ha−1for late‐planted crops. Nitrogen accumulation at final spring sampling ranged from 44 to 144 kg ha−1for early planted crops and from 10 to 99 kg ha−1for late‐planted crops. The low C/N ratio of wheat–vetch treatment compared with wheat monoculture at final sampling indicated the potential for vetch to increase the N content of the mixture.
Soybean Varietal Response to Liquid Swine Manure Application
Authors: Schmidt John P. , Lamb John A. , Schmitt Michael A. , Randall Gyles W. , Orf James H. , Gollany Hero T.
Published: July 2010

Applying manure to soybean [Glycine max(L.) Merr.] as a routine management practice requires additional information about cultivar‐dependent responses. Our objective was to determine seed yield, dry matter accumulation, N accumulation, and lodging responses for a cross‐section of adapted public and private soybean cultivars when liquid swine (Sus scrofa) manure was applied. Field studies were conducted at seven locations in southern Minnesota during 1996 and 1997. Whole‐plot treatments included three swine manure rates (zero, low, and high) injected with sweeps to a soil depth of 13 cm before planting. Split‐plot treatments consisted of 12 public and private soybean cultivars. Average seed yield for all cultivars at three of seven locations was generally positive, increasing on average 1.4 kg kg−1of applied available N. A significant manure rate × cultivar interaction was observed for lodging scores, but increased lodging was not related to any change in yield. Seed yield decreased with increasing manure rates at a seventh location, where there was a history of white mold [Sclerotinia sclerotiorum(lib.) d. By.] incidence. At this location, seed yield for the control was 0.20 Mg ha−1greater than seed yield from either manure rate, and response to manure application was not the same for every cultivar. Except for this latter site, seed yield response to increasing manure rate was either favorable or innocuous, despite increased lodging. Manure application to soybean appears to be an acceptable management practice regardless of cultivar, except when the application exacerbated an already present disease pressure.
Extraction of Subsoil Nitrogen by Alfalfa, Alfalfa–Wheat, and Perennial Grass Systems
Authors: Entz Martin H. , Bullied W. John , Forster David A. , Gulden Robert , Vessey J. Kevin
Published: July 2010

The role of alfalfa (Medicago sativaL.) in extracting NO3–N from deep soils of areas with cold, short growing seasons, such as western Canada, is not well understood. A study was established in 1990 to determine NO3–N extraction ability to 300 cm; initial soil NO3–N concentrations were high (>8 mg kg−1). Systems included continuous alfalfa; annual rotations of spring wheat (Triticum aestivumL.), field pea (Pisum sativumL.), and barley (Hordeum vulgareL.); a native‐grass system [big bluestem (Andropogon gerardiVitman) and western wheatgrass (Agropyron smithiiRydb.)]; and continuous fallow. The annual rotation effectively lowered NO3–N to <2.3 mg kg−1in the 30‐ to 90‐cm depth. By the 4th yr, alfalfa had reduced NO3–N concentrations to <3.8 mg kg−1for the 30‐ to 240‐cm increment. The greatest NO3–N extraction benefits of alfalfa were realized in the 4th yr at a maximum soil depth of 270 cm. Subsoil NO3–N concentration increased in the continuous alfalfa between the 4th and 6th yr. Greater NO3–N extraction occurred with the native‐grass treatment compared with continuous alfalfa in the 0‐ to 120‐cm soil depth; however, similar extraction patterns existed below 120 cm. A system involving 4 yr of alfalfa followed by two wheat crops resulted in the lowest subsoil NO3–N concentration, even lower than the continuous alfalfa and native‐grass systems. It was concluded that subsoil NO3–N extraction with alfalfa was maximized when alfalfa was rotated with annual crops.
Economics of Fall Tillage for Early and Conventional Soybean Plantings in the Midsouthern USA
Authors: Heatherly Larry G. , Spurlock Stan R.
Published: July 2010

Conventional soybean [Glycine max (L.) Merr.] production in the midsouthern USA has involved planting Maturity Group (MG) V and later cultivars in May and later months in a seedbed that has been shallow‐tilled in the fall or spring just before planting. Moisture deficits that frequently occur from April through September reduce yield of soybean cultivars used in this traditional production system. Field experiments using MG IV ‘DP 3478’ and MG V ‘Hutcheson’ were conducted at Stoneville, MS (33°26′ N lat) on Sharkey clay (very fine, smectitic, thermic chromic Epiaquert) in 1995, 1996, and 1998. The objective was to compare yields and economic returns from April and May or later plantings of MG IV and V soybean cultivars grown without irrigation on clay soil following shallow (ST) and deep (DT) fall tillage. Net returns were calculated as the difference between income and all direct and indirect costs, excluding those for land, management, and general farm overhead. Costs for the DT treatment were $22 to $27 ha−1 greater than those for ST. Yields and net returns resulting from DT were greater than those from ST in 1 yr. Yields and net returns from April plantings were greater than those from May or later plantings in 2 of the 3 yr. These results indicate that April plantings will result in greater yields and net returns over the long term, but increased profits from DT are infrequent.
Interpreting Treatment × Environment Interaction in Agronomy Trials
Authors: Vargas Mateo , Crossa Jose , Van Eeuwijk Fred , Sayre Kenneth D. , Reynolds Matthew P.
Published: July 2010

Multienvironment trials are important in agronomy because the effects of agronomic treatments can change differentially in relation to environmental changes, producing a treatment × environment interaction (T × E). The aim of this study was to find a parsimonious description of the T × E existing in the 24 agronomic treatments evaluated during 10 consecutive years by (i) investigating the factorial structure of the treatments to reduce the number of treatment terms in the interaction and (ii) using quantitative year covariables to replace the qualitative variable year. Multiple factorial regression (MFR) for specific T × E terms was performed using standard forward selection procedures for finding year covariables that could replace the factor year in those T × E terms. Subsequently, we compared the results of the final MFR with those of a partial least squares based analysis to achieve extra insight in both the T × E and final MFR model. The MFR model with a stepwise procedure used in this study for describing the T × E showed that the most important interaction with year was that due to different N fertilizer levels and the most important environmental variables that explained year × N interaction were minimum temperatures in January, February, and March and maximum temperature in April. Evaporation in December and April were important covariables for describing year × tillage and year × summer crop interactions, whereas precipitation in December and sun hours in February were important for explaining the year × manure interaction. We also discuss the parallels with extended additive main effect and multiplicative interaction analysis. Biological interpretation of the results are provided.
Estimating Ammonia Loss from Sprinkler‐Applied Swine Effluent
Authors: Al‐Kaisi Mahdi M. , Waskom Reagan M.
Published: July 2010

Volatilization of NH3 from sprinkler‐applied effluent is a major N loss pathway in the Great Plains region, but there is disagreement as to how much of the total NH4–N applied in effluent is lost. The objectives of the study were to determine NH3 loss during sprinkler application and from soil and to determine the amount of mineral N available to the crop over a series of swine effluent application rates, effluent sources, and field conditions. A 3‐yr study was conducted on fields near swine (Sus scrofa) production operations. A mass balance method was used to estimate N loss during and after effluent application at rates of 1.3, 1.9, and 2.5 cm. Change in inorganic N concentration in effluent captured below the sprinkler was used to estimate volatilization during application, and the change in inorganic N concentration in soil (before and 72 h after application) was used to estimate N loss from soil. Ammonia loss during application ranged from 8 to 27% of the total NH4–N in the effluent due to drift and volatilization. The range of estimated N loss from the soil varied from 24 to 56% of the NH4–N in the applied effluent. The total N loss from both the sprinkler application and the soil ranged from 32 to 83%, with an average loss of approximately 58%. Effluent N concentration did not significantly impact the percent of N lost, while air temperature and wind speed were significant variables in the percent of N lost.
Row Width and Weed Management Systems for Early Soybean Production System Plantings in the Midsouthern USA
Authors: Heatherly Larry G. , Spurlock Stan R. , Elmore C. Dennis
Published: July 2010

Management inputs that maximize economic return from the early soybean [Glycine max (L.) Merr.] production system (ESPS) in the midsouthern USA have not been evaluated fully. Field studies were conducted at Stoneville, MS (33°26′ N lat) to determine effect of weed management on yield and net return from maturity group (MG) IV and MG V cultivars grown in the ESPS in narrow rows (NRs; 50‐cm width) and wide rows (WRs; 100‐cm width) in nonirrigated (NI) and irrigated (IRR) environments. Use of NRs vs. WRs resulted in less weed cover at soybean maturity, but this was associated with greater weed management costs in NRs. In NI, choice of MG for ESPS plantings and choice of row width for MG V cultivars was arbitrary, but the MG IV cultivar did best in NR. Use of both pre‐emergent (PRE) and postemergent (POST) broadleaf weed management in both NRs and WRs resulted in lower net returns. In IRR, NRs outyielded WRs, the MG IV cultivar yield equaled or exceeded the MG V yield in NRs, and the MG V cultivar outyielded the MG IV cultivar in WRs in both years. Differences in net returns followed yield differences. Use of POST‐only broadleaf and grass weed management resulted in the highest net returns across the 2 yr. Thus, a MG IV cultivar planted in NRs with POST weed management appears to be the most profitable option in IRR‐ESPS plantings. If WRs are required for management reasons in the ESPS, a MG V cultivar should be used.
Soybean Yield as Affected by Biomass and Nitrogen Uptake of Cereal Rye in Winter Cover Crop Rotations
Authors: Ruffo Matías L. , Bullock Donald G. , Bollero Germán A.
Published: July 2010

The inclusion of cereal rye (Secale cerealeL.) as winter cover crop (WCC) following corn (Zea maysL.) has been suggested as a valuable nutrient management tool in the typical corn–soybean [Glycine max(L.) Merr.] rotation of the U.S. Midwest. However, little information is available on the effects of rye WCC on the soybean crop. The objectives of this study were to quantify biomass and nitrogen (N) uptake of rye WCC and to evaluate the effect of rye WCC on soybean yield. The effects of four rotations (corn/soybean, hairy vetch–corn/rye–soybean, rye–corn/rye–soybean, and hairy vetch + rye biculture–corn/rye–soybean) on soil residual NO3–N content, rye biomass, N content, and C/N ratio, soil residue cover, soybean light interception, and grain yield were investigated at Urbana and Brownstown, IL. Rye N content was highly correlated with soil residual NO3–N content (r= 0.64,p< 0.0001). Rotations that only included hairy vetch (Vicia villosaL.) reached maximum N content at lower corn N rates compared with rotations with rye. Soybean light interception at R1, R4, and R6 growth stages and grain yield were not affected by the treatments. Rye WCC planted after corn appears to take up a significant proportion of residual NO3–N without affecting soybean grain yield, providing an environmental service to the agroecosystem.
Supplemental Nitrogen Effect on Broiler‐Litter–Fertilized Cotton
Authors: Sistani K. R. , Rowe D. E. , Johnson J. , Tewolde H.
Published: July 2010

Nitrogen nutrition plays a critical role in cotton (Gossypium hirsutum L.) production. However, increasing N fertilization may not always be desirable because production problems occur when N supply exceeds the crop requirement. A field experiment was conducted during 2000–2002 to study the optimal quantity of N needed from litter or combination of litter N and supplemental inorganic N for optimum cotton yield production. Poultry litter (2.24 Mg ha−1 equivalent to 1 ton acre−1) has been applied to the site annually for the past 20 yr. The experiment included four inorganic N rates (0, 34, 67, and 101 kg N ha−1) as sidedress in addition to litter application. The smallest overall average cotton lint yield of 562 kg ha−1 was obtained during 2000 (an exceptionally dry year) followed by 1551 kg ha−1 in 2001 and 880 kg ha−1 in 2002. The supplemental N application did not impact the cotton yield in 2 out of 3 yr. In the 2000 growing season, cotton yield was significantly greater for 0 and 34 than 67 and 101 kg N ha−1 rates. This indicates the negative effect of excess N application on cotton yield under drought conditions. However, under more favorable soil moisture conditions, no significant yield differences were observed by increasing the supplemental N rate up to 101 kg N ha−1. The 2.24 Mg ha−1 broiler litter application to all plots before planting each year provided approximately 80 kg N ha−1, which proved to be adequate in three consecutive years for optimum cotton production under a no‐till system.
Agroecosystem Performance during Transition to Certified Organic Grain Production
Authors: Delate Kathleen , Cambardella Cynthia A.
Published: July 2010

The 2002 U.S. Farm Bill offers incentives to support the transition from conventional to certified organic production. Research‐based recommendations must be developed for suitable crop rotations that provide high yields, grain quality, and adequate soil fertility during the transition. We compared replicated conventional and organic systems, using identical crop varieties, during the 3‐yr transition period and the fourth year following a full rotation of organic corn (Zea maysL.)–soybean [Glycine max(L.) Merr.]–oat (Avena sativaL.)–alfalfa (Medicago sativaL.) to determine which rotation was associated with the lowest risk during transition. Organic feed corn yields at the Neely–Kinyon long‐term agroecological research (LTAR) site in Greenfield, IA, were equivalent to conventional yields in the transition years, and in the fourth year, the organic corn yield of 8.1 Mg ha−1in the longest rotation was greater than the conventional corn yield of 7.1 Mg ha−1in the conventional corn–soybean rotation. Organic and conventional soybean yields were similar in the 3 yr of transition. Organic soybean yield of 3.0 Mg ha−1exceeded the conventional yield of 2.7 Mg ha−1in the fourth year of organic production. Pre‐ and postharvest soil fertility values were responsive to manure application, but few differences between systems were observed. Grass and broadleaf weed populations varied between the organic and conventional systems each year, but the impact on yield was considered negligible. Corn borer (Ostrinia nubilalis) and bean leaf beetle (Ceratoma trifurcata) populations were similar between systems, with no effect on yield. We conclude that organic grain crops can be successfully produced in the 3 yr of transition to organic, and additional economic benefits can be derived from expanded crop rotations.