• Authors:
    • Stewart,B. A.
    • Blaser,B. C.
    • Mohammed,S.
  • Source: Journal of Crop Improvement
  • Volume: 26
  • Issue: 1
  • Year: 2012
  • Summary: Water for dryland grain production in the Texas panhandle is limited. Agronomic practices such as reduction in plant population or change in sowing time may help increase maize ( Zea mays L.) yield potential. Tiller formation under dryland conditions leads to more vegetative growth and reduced yield. We hypothesized that clump planting dryland maize would reduce environmental stress, tillering, and vegetative growth, and increase harvest index by having more soil water available during grain filling. Clump planting was studied during 2008 at Bushland, Texas. Two plant populations - 30,000 and 40,000 plants ha -1 - and three plant geometries - clumps of three or four plants (3 PPC or 4 PPC) and equally spaced single plants (ESP) - were grown in 75 cm rows. Growing season precipitation was 209 mm. Harvest index (HI) 200-seed mass and harvested ears were higher in 3 PPC and 4 PPC compared with ESP. Three PPC planted at 40,000 plants ha -1 had the highest harvest index of 0.46. The ESP produced 27% more unproductive ears compared with 3 PPC and 4 PPC. Leaf area index (LAI) was 14% more in ESP than in 4 PPC. The lower population produced higher HI and seed mass than the higher population, regardless of geometry. Grain yields were not significantly higher for clumps, yet increased number of productive ears, seed mass, and HI values, suggesting clump geometry may be a good strategy for dryland maize production.
  • Authors:
    • Garcia, T. S.
    • Giannico, G. R.
    • Mueller-Warrant, G. W.
    • Griffith, S. M.
    • Whittaker, G. W.
    • Banowetz, G. M.
    • Pfender, W. F.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 3
  • Year: 2012
  • Summary: Agricultural practices, including tillage, fertilization, and residue management, can affect surface runoff, soil erosion, and nutrient cycling. These processes, in turn, may adversely affect (1) quality of aquatic resources as habitat for amphibians, fish, and invertebrates, (2) costs of treating surface and ground water to meet drinking water standards, and (3) large-scale biogeochemistry. This study characterized the surface water sources of nitrogen (N) (total, nitrate [NO 3-], ammonium [NH 4+], and dissolved organic N) and sediment active within 40 subbasins of the Calapooia River Basin in western Oregon in monthly samples over three cropping years. The subbasins included both independent and nested drainages, with wide ranges in tree cover, agricultural practices, slopes, and soils. Sediment and N form concentrations were tested against weather and agricultural practice variables. Subbasin land use ranged from 96% forest to 100% agriculture. Average slopes varied from 1.3% to 18.9%, and surface water quality ranged from 0.5 to 43 mg L -1 (ppm) total N maxima and 29 to 249 mg L -1 suspended sediment maxima. Total N during the winter was positively related to percentage landcover of seven common agricultural crops (nongrass seed summer annuals, established seed crops of perennial ryegrass [ Lolium perenne L.], tall fescue [ Schedonorus phoenix {Scop.} Holub], orchardgrass [ Dactylis glomerata L.], clover [ Trifolium spp.], and newly planted stands of perennial ryegrass and clover) and negatively related to cover by trees and one seed crop, Italian (annual) ryegrass ( Lolium multiflorum). Results for NO 3- and total N were highly similar. Sediment concentrations were most strongly related to rainfall totals during periods of 4 and 14 days prior to sampling, with smaller effects of soil disturbance. Fourier analysis of total N over time identified four prominent groups of subbasins: those with (1) low, (2) medium, and (3) high impacts of N (up to 2, 8, and 21 mg L -1, respectively) and a strong cyclical signal peaking in December and (4) those with very high impact of N (up to 43 mg L -1) and a weak time series signal. Preponderance of N in streams draining agriculturally dominated subbasins was in the form of the NO 3- ion, implying mineralization of N that had been incorporated within plant tissue following its initial application in the spring as urea-based fertilizer. Since mineralization is driven by seasonal rainfall and temperature patterns, changes in agronomic practices designed to reduce prompt runoff of fertilizer are unlikely to achieve to more than ~24% reduction in N export to streams.
  • Authors:
    • Lauenroth,W. K.
    • Munson,S. M.
    • Burke,I. C.
  • Source: Journal of Arid Environments
  • Volume: 79
  • Year: 2012
  • Summary: Cropping practices in the Great Plains of the U.S. have led to large losses in soil organic carbon (SOC) and nitrogen (N). Land converted to perennial vegetation through the Conservation Reserve Program (CRP) has the potential to recover these losses and sequester anthropogenic carbon. We studied 18 years of SOC and N recovery in CRP fields seeded with native and non-native perennial grasses in the driest portion of the Great Plains. SOC and N under native perennial grasses in the surface soil increased by as much as 200 g C m -2 and 14 g N m -2 in 9 years. However, low plant basal cover in CRP fields limited SOC and N recovery at the field scale to 2 g C m -2 y -1 and 0.02 g N m -2 y -1. After 18 years of recovery, CRP fields seeded with native perennial grasses had 60% of the total SOC and 67% of the total soil N in undisturbed shortgrass steppe, and fields seeded with non-native perennial grasses recovered less. Belowground plant inputs to SOC reached 70-85% under native and 50% under non-native perennial grasses within 18 years. Our results suggest low potential for CRP fields to offset anthropogenic C emissions in semiarid regions under current management practices, but this potential could be enhanced by lengthening CRP contracts or promoting the establishment of perennial vegetation with high basal cover.
  • Authors:
    • Mukhwana, E. J.
    • Norton, U.
    • Norton, J. B.
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 2
  • Year: 2012
  • Summary: Soils typically show 20 to 40% decline in soil organic carbon (SOC) due to cultivation, most of it in the first 10 yr, but studies on SOC depletion may actually underestimate losses of the original SOC. Starting 40 to 50 yr ago, expanding use of non-inversion tillage, fertilizers, and herbicides lead to reduced disturbance and increased residue production that undoubtedly began recovery of SOC depleted during previous decades when farmers used only intensive tillage to control weeds and stimulate release of nutrients from crop residues. We measured SOC and total N stocks, density fractions, and labile C and N at 10 study sites in two rain-fed production areas in southeastern Wyoming. Systems evaluated include historic inversion-tillage-based winter wheat ( Triticum aestivum L.)-fallow with no inputs, conventional winter wheat-fallow, minimum- and no-till continuous rotations and permanent grass cover. Results were then compared to SOC under nearby native grasslands. Soils beneath historic wheat-fallow were the most depleted in SOC, with 13.8 and 17.6 Mg C ha -1 in the upper 30 cm at the two study areas, or 37% of the SOC under the two native sites. Soil OC contents were statistically similar across conventional, minimum-till, and no-till systems, ranging from 64 to 78% of native SOC levels, and significantly higher under permanent grass, with both sites having 90% of native SOC levels. Free light fraction organic carbon (LFOC) contents were lowest beneath the historic system, but increased in systems with fewer disturbances. When normalized by SOC and total N, the labile C and N pools generally increased with increasing disturbance, especially microbial biomass carbon (MBC) and dissolved organic carbon (DOC). Soil OC contents under the historic, inversion tillage system were much lower relative to native grasslands than found in other studies, which, together with other findings, suggest that SOC levels have begun to recover under the modern conventional system. Free LFOC and labile pool C and N contents indicate that conservation tillage systems in place for a relatively short time are facilitating further recovery of SOC.
  • Authors:
    • Paustian, K.
    • Ogle, S. M.
    • Swan, A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 149
  • Year: 2012
  • Summary: The efficacy of no-till agriculture for increasing C in soils has been questioned in recent studies. This is a serious issue after many publications and reports during the last two decades have recommended no-till as a practice to mitigate greenhouse gas emissions through soil C sequestration. Our objective was to investigate the possibility that the lack of C increase in some no-till systems may be due to changes in crop productivity and subsequent C input to soils. A meta-analysis of 74 published studies was conducted to determine if crop production varies between no-till and full tillage management. The results were used to estimate the change in C input due to no-till adoption and the influence on soil organic C stocks at steady-state using the Century model. We found that crop productivity can be reduced with adoption of no-till, particularly in cooler and/or wetter climatic conditions. The influence varies, however, and crop productivity can even increase in some regions following adoption of no-till. In cases where crop production and C inputs decreased due to no-till, the potential reduction in soil organic C stocks was offset by a decrease in soil C decomposition rates, except in cases where C inputs declined by 15% or more. Challenges still remain for understanding the full impact of no-till adoption on soil organic C stocks, such as changes on C inputs in deeper subsurface horizons, the influence of variation in NT seeding methods on soil disturbance, and changes in SOM stabilization due to saturation limits in mineral soil fractions, which may further modify net C storage in soils.
  • Authors:
    • Moriasi, D.
    • Steiner, J. L.
    • Starks, P. J.
    • Saleh, A.
    • Osei, E.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 2
  • Year: 2012
  • Summary: No-till farming has been identified as an important conservation practice with potential to improve soil quality and protect water quality. However, adoption of new tillage and production practices is determined by numerous economic and noneconomic factors in addition to land stewardship. The objective of this study was to assess the effects of fuel costs and crop yield on farm-level economics in no-till systems in comparison with other tillage systems for wheat production in southwestern Oklahoma. The Farm-level Economic Model, an annual economic simulation model, was used in conjunction with survey data from the Fort Cobb Reservoir Watershed in southwestern Oklahoma to determine impacts of alternative tillage practices on farm profits. Sensitivity analysis was performed using plausible ranges in diesel prices, winter wheat grain yields, herbicide costs, labor wages, and farm size. The results indicate that if winter wheat grain yields are not significantly impacted by tillage systems, no-till would be more profitable than conventional tillage or the current mix of tillage practices in the watershed. Only when there is a significant wheat yield penalty associated with no-till (10% or greater) might no-till be less profitable than conventional tillage or the status quo at reasonably high fuel prices. In general, for each 1% improvement in wheat yields under no-till relative to conventional tillage, no-till farm profits improve by US$7 ha -1 (US$3 ac -1) on farms that produce only winter wheat and an average of US$2.50 ha -1 (US$1 ac -1) if averaged across all farms in the Fort Cobb Reservoir Watershed, including those that do not produce winter wheat. The study also finds that higher diesel prices, higher labor wages, lower herbicide costs, and smaller farm sizes are all relatively advantageous to no-till.
  • Authors:
    • Kremer, R. J.
    • Anderson, S. H.
    • Paudel, B. R.
    • Udawatta, R. P.
  • Source: Agroforestry Systems
  • Volume: 84
  • Issue: 2
  • Year: 2012
  • Summary: Soil enzyme activities and water stable aggregates have been identified as sensitive soil quality indicators, but few studies exist comparing those parameters within buffers, grazed pastures and row-crop systems. Our objective was to examine the effects of these land uses on the activities of selected enzymes (beta-glucosidase, beta-glucosaminidase, fluorescein diacetate (FDA) hydrolase, and dehydrogenase), proportion of water stable aggregates (WSA), soil organic carbon and total nitrogen content. Four management treatments [grazed pasture (GP), agroforestry buffer (AgB), grass buffer (GB) and row crop (RC)] were sampled in 2009 and 2010 at two depths (0 to 10- and 10 to 20-cm) and analyzed. Most of the soil quality indicators were significantly greater under perennial vegetation when compared to row crop treatments. Although there were numerical variations, soil quality response trends were consistent between years. The beta-glucosaminidase activity increased slightly from 156 to 177 g PNP g -1 dry soil while beta-glucosidase activity slightly decreased from 248 to 237 g PNP g -1 dry soil in GB treatment during 2 years. The surface (0-10 cm depth) had greater enzyme activities and WSA than sub-surface (10-20 cm) samples. WSA increased from 178 to 314 g kg -1 in row crop areas while all other treatments had similar values during the 2 year study. The treatment by depth interaction was significant ( P<0.05) for beta-glucosidase and beta-glucosaminidase enzymes in 2009 and for dehydrogenase and beta-glucosaminidase in 2010. Soil enzyme activities were significantly correlated with soil organic carbon content ( r≥0.94, P<0.0001). This is important because soil enzyme activities and microbial biomass can be enhanced by perennial vegetation and thus improve several other soil quality parameters. These results also support the hypothesis that positive interactions among management practices, soil biota and subsequent environmental quality effects are of great agricultural and ecological importance.
  • Authors:
    • Way, T. R.
    • Kleinman, P. J. A.
    • Moore, P. A.
    • Pote, D. H.
  • Source: Journal of Agricultural Science
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: Poultry manure provides a rich organic nutrient source to fertilize crops and help neutralize soil acidity. However, the usual practice of broadcasting litter on the surface of pastures and other no-till systems can degrade water quality by allowing nutrients to be transported from fields in surface runoff, while much of the ammonium-N volatilizes and escapes into the atmosphere. In a previous study, we used a subsurface banding technique to move litter from the soil surface into the root zone with minimal disturbance of the grass, thatch, and soil structure; and found that nutrient losses decreased substantially. Because subsurface banding increased retention of nutrients and water in the soil, we conducted follow-up research to compare crop yield and quality from this litter application method to those from the conventional surface broadcasting method. The objectives were to determine effects of subsurface application on perennial forage yield, quality, and temporal yield distribution during the growing season. Field plots were located on silt loam soil (8-10% slopes) with well-established bermudagrass ( Cynodon dactylon L. Pers.). Poultry litter was applied (6.7 Mg ha -1, dry weight) by one of two methods: surface broadcast manually or subsurface banded using a tractor-drawn prototype implement. Each treatment was replicated three times. There were also three control plots that received no litter. Results showed that subsurface application generally increased forage quality and yield, especially in the latter part of the growing season when forage production from surface-applied litter began to decline. Under the growing conditions in this study, subsurface application increased mean forage yield by as much as 40%.
  • Authors:
    • Presley, D. R.
    • Sindelar, A. J.
    • Buckley, M. E.
    • Mengel, D. B.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: Grain sorghum [ Sorghum bicolor (L.) Moench] is an important grain crop grown in both highly productive and marginal areas in the central Great Plains because of the crop's ability to use the erratic precipitation observed in this region. More effective capture and storage of this limited rainfall is needed to improve the productivity and profitability of dryland agriculture. The objective of this study was to determine the effects of long-term tillage and N fertilization on soil physical and hydraulic properties after long-term continuous grain sorghum production. Variables included conventional tillage (CT) and no-till (NT) and four rates of N fertilizer. Selected soil quality indicators included soil organic carbon (SOC), bulk density (BD), wet aggregate stability (WAS), and ponded infiltration. No-till accumulated more SOC in the surface 0 to 5 cm, and was less dense at all depths than CT. When tillage was compared across all N rates, NT contained 30% greater SOC than CT at the 0 to 5 cm. Mean weight diameter (MWD) was larger with increasing N fertilization and eliminating tillage. Ponded infiltration rates were greatest for the high N fertilization rate under NT, and lowest for the 0 kg N ha -1 rate under CT. In this long-term grain sorghum system, increasing N fertilization rate and NT both positively affected soil physical properties. These improvements in hydraulic properties will aid in more effectively capturing unpredictable precipitation, and further underscore the utility of NT management practices for the central Great Plains region.
  • Authors:
    • Kornecki, T. S.
    • Place, G. T.
    • Reberg-Horton, S. C.
    • Grossman, J. M.
    • Meijer, A. D.
    • Price, A. J.
    • Webster, T. M.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: 1
  • Year: 2012
  • Summary: Organic systems in the southeastern USA offer unique challenges and solutions to crop production due to regional soil and climate characterized by highly weathered soil types, high precipitation and the capacity to grow cover crops in the winter. Recently, the interest of producers and researchers in high-residue cover crops and conservation tillage systems has increased. Various designs of the roller-crimper to manage cover crops have been invented and demonstrated to growers in the southeastern region of the USA over the past 17 years. The impacts of high-residue cover crop mulches on the agronomic systems in the region are diverse. Legume cover crops assist with meeting N demand from cash crops though they decompose rapidly and are seldom sufficient for N demanding crops such as corn. Cereal cover crop mulches can have the opposite effect by immobilizing N and have a longer impact on soil moisture and weed dynamics. While undesirable for many crops, N immobilization is one possible mechanism for weed suppression in legume cash crops planted into cereal residues. Other cover crop weed suppression mechanisms include physical impedance, light availability, allelopathy and microclimate effects. Regardless of the cause, successful weed control by mulches is highly dependent on having substantial biomass. The southeastern region is capable of producing cover crop biomass in excess of 9000 kg ha(-1), which is sufficient for weed control in many cash crops, although supplementary weed control is sometimes necessary. Long-term data are needed to predict when farmers should add supplementary weed control. More work is also needed on how much additional N is required for the cash crops and how best to deliver that N in a high-residue environment using organic sources.