• Authors:
    • Nelson, K. A.
    • Udawatta, R. P.
    • Motavalli, P. P.
    • Bailey, N. J.
  • Source: Agroforestry Systems
  • Volume: 77
  • Issue: 2
  • Year: 2009
  • Summary: The potential for agricultural soils to act as a sink and sequester carbon (C) or a source and emit carbon dioxide (CO2) is largely dependent upon the agricultural management system. The establishment of permanent vegetation, such as trees and grass contour buffer strips, may cause accumulation of above- and below-ground C over time, thereby acting as a sink for tropospheric CO2. However, the effects of contour grass strips and grass-tree strips (agroforestry) on soil CO2 emissions have not been extensively studied in row-crop watersheds in the temperate regions. The objective of this study was to determine the effects of agroforestry and grass contour buffer strips and landscape position on soil surface efflux rate of CO2 in three adjacent agricultural watersheds with claypan soils in northeast Missouri. The three watersheds were in a corn-soybean rotation, and contained (1) cropped only (CR), (2) cropped with grass contour strips (GR), or (3) cropped with tree-grass contour strips (AF) management systems. Soil surface CO2 efflux was measured throughout the 2004 growing season at the upper (UBS), middle (MBS), and lower (LBS) backslope landscape positions within the three watersheds. The cumulative soil CO2 production was lowest in the CR (0.9 kg CO2-C m-2) compared to the AF (1.5 kg CO2-C m-2) and GR watersheds (1.5 kg CO2-C m-2). The lower backslope position (1.6 kg CO2-C m-2) across all three watersheds produced 32 and 40% greater cumulative soil CO2 than the upper and middle backslope positions, respectively. A 72-day incubation study determined the effects of 40, 60, 80, and 100% soil water-filled pore space (WFPS) and N rate (0 and 1.39 g KNO3 kg soil-1) on soil CO2 efflux from bulk soil collected under each management system. The cumulative CO2 production was highest in the grass soil (1,279 mg CO2-C kg soil-1) compared to the agroforestry (661 mg CO2-C kg soil-1) and cropped (483 mg CO2-C kg soil-1) soils regardless of WFPS and N rate. The highest cumulative CO2 production for the grass soil (1,279 mg CO2-C kg soil-1) occurred at 80% WFPS, and was approximately 2 to 2.6 times greater than the agroforestry and cropped soils at 80% WFPS. The results of this study indicate that conservation management practices, such as grass and grass-tree contour buffer strips, and landscape position affect soil surface CO2 production and accumulation of soil organic C that may influence soil C sequestration.
  • Authors:
    • Benbrook, C.
  • Source: Critical Issue Report: The First Thirteen Years
  • Year: 2009
  • Summary: Th is report explores the impact of the adoption of genetically engineered (GE) corn, soybean, and cotton on pesticide use in the United States, drawing principally on data from the United States Department of Agriculture. Th e most striking finding is that GE crops have been responsible for an increase of 383 million pounds of herbicide use in the U.S. over the first 13 years of commercial use of GE crops (1996-2008).
  • Authors:
    • Lal, R.
    • Blanco-Canqui, H.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 2
  • Year: 2009
  • Summary: Franzluebbers (2009) is right about the need for a more intensive soil sampling, "repeated sampling with time,"and "stratified sampling" as well as for the use of multiple fields and collection of larger number of pseudoreplicates to overcome the high field variability in soil organic carbon (SOC) pools within each Major Land Resource Area (MLRA). The selected fields were representative of each MLRA in terms of soil type, slope, and management, but it is correct that a single soil would not capture all the variability in soil and management for the whole MLRA. This study was not intended to relate the data from the single soil to the whole MLRA but rather to emphasize the differences in SOC sequestration rates among the three management systems within each soil.
  • Authors:
    • McNeill, A.
    • Sommer, R.
    • Ibrikci, H.
    • Ryan, J.
  • Source: Advances in Agronomy
  • Volume: 104
  • Year: 2009
  • Summary: This review examines the varied aspects of N in the soils and cropping systems as reflected by research at The International Center for Agricultural Research in the Dry Areas (ICARDA) in Syria in collaboration with other countries of the West Asia-North Africa region, especially in Morocco and other countries north and south of the Mediterranean. The synthesis, therefore, reflects a broad overview of conditions that impinge an N nutrition of crops and the evolution of N research achievements since the advent of commercial fertilization over three decades ago. With few exceptions, the soils of the Mediterranean region are low in organic matter and consequently in the reserves of total N, thus posing a limit of growing crops without fertilizer N or biological N fixation (BNF) through legumes. Soil calibration studies established the value of the soil nitrate test as a predictor of crop response with field trials to establish application rates for the main crops. Applicability is influenced by depth of sampling and the extent of mineralization. Dryland crop responses to N varied widely throughout the region from 30 to 150 kg N ha -1, being dependent on soil N status and seasonal rainfall as the major determinant of yields. Splitting the N application was only advantageous in higher rainfall areas. Residual N from BNF by food and forage legumes influenced soil N supply for cereals and relative responses to N fertilizer. The contribution of rhizobia fixation to all the major legumes was quantified using 15N along with management factors that influenced BNF by legumes. Where legumes were newly introduced to a region, rhizobial inoculation was considered necessary. With cereal responses to fertilizer N, differences between varieties were highlighted. Where urea or ammonium-N fertilizers were used, volatilization was the main loss mechanisms rather than leaching or denitrification. Considerable work was done on N use within crop rotation systems and components of the N cycle defined along with inputs from urine and feces from grazing animals. Forage legumes were shown to enhance total soil N and both labile and biomass N, with the least influence from fallow. These N forms were shown to fluctuate during the year as moisture and temperature conditions changed. Fertilizer N use had a positive effect on grain quality with increased protein, as well as soil organic matter (SOM) and thus soil quality. The significant change of the gradual introduction of supplemental irrigation in traditional rainfed cropping areas and its implications for use of models to describe the complex nature of N in dryland cropping systems was described. With the likelihood of a continuation of intensification of the dryland cropping systems in the Mediterranean region, N fertilizer use will inevitably increase and along with it the need for greater use efficiency in the interest of production economics and the environment. While limited use has been made of modeling of N, this approach is likely to be of more significance in integrating the varied facets of N under Mediterranean cropping conditions.
  • Authors:
    • Gentry, T.
    • Aitkenhead-Peterson, J.
    • Gonzalez-Chavez, M.
    • Zuberer, D.
    • Hons, F.
    • Loeppert, R.
  • Source: Soil & Tillage Research
  • Volume: 106
  • Issue: 2
  • Year: 2009
  • Summary: Tillage and crop rotation/intensity can influence soil biological properties and relevant soil processes including C sequestration. This study determined the effects of long-term (25 years) no till (NT) and conventional tillage (CT) management and cropping sequence [continuous wheat (CW; Triticum aestivum L.) and a rotation of sorghum ( Sorghum bicolor L. Moench), wheat and soybean (RW; Glycine max L. Merr)] on soil microbial community structure and labile and recalcitrant microbial bio-products in central Texas. Fatty acid methyl ester (FAME) profiles, microbial biomass (MB-C, -N and -P), hot water extractable soil carbohydrates (HWE-SC) and easily extracted- (EE-) and total-glomalin-related soil proteins (T-GRSP) were analyzed. Principal component analysis of the FAME data indicated that crop management modified and selected microbial populations. In general, NT-RW resulted in the greatest richness and biodiversity of the total microbial community, soil organic C, MB-P, HWE-SC, EE- and T-GRSP. No tillage increased labile and more recalcitrant bio-products, soil organic C and total N compared to CT. The soil microbial biomass C:N:P ratio, an indicator of ecosystem nutrient limitation, suggested that the CT-RW treatment may have a soil P limitation, which was not observed in the other treatments. The treatments preferentially selected for different microbial communities, which generated microbial products that significantly influenced soil C and N retention. Our results suggested that NT in conjunction with crop rotation (RW) can be recommended for increased soil C sequestration.
  • Authors:
    • Karayel, D.
  • Source: Soil & Tillage Research
  • Volume: 104
  • Issue: 1
  • Year: 2009
  • Summary: The purpose of this research was to examine the performance of a modified precision vacuum seeder for no-till sowing of maize ( Zea mays L.) and soybean ( Glycine max L.) following wheat ( Triticum aestivum). A wavy-edged disc and side gauge wheels were fabricated and mounted to each unit of a common precision vacuum seeder (with a hoe opener on one row unit and a double disc-type opener on another row unit) and used to sow at three forward speeds (1.0, 1.5 and 2.0 m s -1). Multiple index, miss index, quality of feed index and precision of the distribution of the seeds along the length of the row, sowing depth uniformity, mean emergence time and percent emergence were determined. Sowing depth uniformity, mean emergence time and percent emergence of both maize and soybean seeds were decreased and precision of the distribution of the seeds along the length of the row was increased as a result of increasing forward speed. The distribution of the seeds along the length of the row, sowing depth uniformity and percent emergence of the seeder equipped with the double disc-type opener was better than the seeder equipped with the hoe-type opener. The precision of the distribution of the seeds along the length of the row for forward speeds of 1.0 and 1.5 m s -1 experienced in this study was well below 29%, and therefore is acceptable for both maize and soybean seeds. The modified precision vacuum seeder generally performed best using the double disc-type furrow opener at the forward speed of 1.0 m s -1, based on the distribution of the seeds along the length of the row, sowing depth uniformity, and percent emergence.
  • Authors:
    • Mastrorilli, M.
    • Katerji, N.
  • Source: European Journal of Agronomy
  • Volume: 30
  • Issue: 2
  • Year: 2009
  • Summary: The effect of soil texture on water use efficiency (WUE) was analyzed for six crops cultivated on loam and clay soils. Results were obtained after a long-term study, carried out in a lysimetric set-up, in conditions of experimental neutrality (climate, agro-techniques, and variety were the same for each crop) with the sole exception of the soil texture, which was the variable to be studied. In the case of potato, corn, sunflower, and sugar beet, WUE was reduced significantly when crops were grown in clay soil. The reductions ranged from 22% to 25%. The decrease of WUE in clay soil was coupled with significant reductions in yield and in ET, except in the case of the corn crop. The reduction in WUE in corn depended solely on the yield decrease. A 10% decrease in WUE values was also observed for the soy-bean and tomato grown in clay soil, but it was not statistically significant. Different causes which may reduce the WUE values observed in the clay soil are discussed. It seems coherent to hypothesize that, during the active growing phase, a deficit in water uptake occurs in the plants growing in the clay soil. This hypothesis is consistent with the observations of stomatal conductance, daily evapotranspiration, and leaf surface. In conclusion, the operative development of this study is outlined.
  • Authors:
    • Bergtold, J. S.
    • Raper, R. L.
    • Price, A. J.
    • Kornecki, T. S.
  • Source: Applied Engineering in Agriculture
  • Volume: 25
  • Issue: 6
  • Year: 2009
  • Summary: In a weed-free field with ideal weather conditions, a cash crop can be planted 3 weeks after rolling a mature cereal rye winter cover crop without using herbicides. However, cloudy and wet weather can delay the rolling and/or desiccation of rye, thereby delaying cash crop planting which can negatively impact yield. One effective way to reduce the time between rolling and planting is to spray herbicide while rolling. However, a continuous spray may not be required if a roller/crimper is used due to the additive effect of the roller. Two different methods of applying glyphosate (Roundup (TM)) to rolled rye were compared. First, a felt strip saturated with herbicide was attached to the roller's crimping bar to provide glyphosate application with every crimp. The second method consisted of a boom (five nozzles controlled by solenoid valves) mounted on the roller applying a spray continuously, and intermittent spray every second crimp, or every fourth crimp. The average results over three growing seasons showed that 7 days after rolling, rye termination rates for all rolled/glyphosate treatments surpassed 90% (91% for glyphosate saturated felt strip and 98% for continuous spray), exceeding the termination rates for rye recommended to planting cash crops into rye residue cover. For the roller/crimper alone and the non-treated check (standing rye), termination rates were 82% and 54%, respectively. Since spraying glyphosate every fourth crimp provided a 93% termination rate one week after rolling, this method may facilitate planting the cash crop in a timely fashion while reducing input costs. Economic savings of $12.63 to $36.87 ha(1) may be attained by incorporating herbicide applications with rolling activities. One and two weeks after the rolling treatment, volumetric soil moisture content for all rolled rye/chemical treatments were significantly higher than the non-treated check.
  • Authors:
    • Kremer, R. J.
    • Kussman, R.
  • Source: Agroforestry comes of age: putting science into practice. Proceedings of the 11th North American Agroforestry Conference, Columbia, Missouri, USA, 31 May - 3 June, 2009
  • Year: 2009
  • Summary: Intercropping alleys of agroforestry systems provides an income source until the tree crop produces harvestable yields. However, cultivation of annual crops soil organic matter and increases soil erosion, especially on sloping landscapes. Perennial crops maintain a continuous soil cover, maximize water infiltration, minimize soil erosion, and improve overall soil quality. The objective of this on-farm study was to assess the effects of a perennial legume, kura clover ( Trifolium ambiguum), on various soil quality parameters in a recently established pecan ( Carya illinoinensis) orchard. The pecan-kura clover agroforestry system was established on deep loess soils of the Missouri River hills. These silt loams are on 3 to 10% slopes and can be highly erosive. Kura clover, intercropped eight years after pecan planting, was selected based on its perennial growth habit, nitrogen-fixing ability, winter hardiness, high forage quality, and soil conservation properties. Kura clover was seeded in 2002 and harvested for hay annually beginning 2003. During this period soil organic matter and activities of selected soil enzymes have steadily increased compared with cultivated and grass pasture control soils. Water-stable aggregation improved by 50%. Results illustrate that kura clover as the interplanted component improved soil fertility and biological activity through increased organic matter and improved soil structure, and yielded high quality forage valuable for the cattle-feeding operation. Pecan trees thrive in this system partly because soil quality is maintained or improved and, unlike other "living mulch" systems in which cover crops may suppress the main crop, kura clover does not compete with tree growth.
  • Authors:
    • Bernards, M. L.
    • Wilson, R. G.
    • Jordan, D. L.
    • Wilcut, J. W.
    • Shaw, D. R.
    • Owen, M. D. K.
    • Weller, S. C.
    • Johnson, W. G.
    • Kruger, G. R.
    • Young, B. G.
  • Source: Weed Technology
  • Volume: 23
  • Issue: 1
  • Year: 2009
  • Summary: Corn and soybean growers in Illinois, Indiana, Iowa, Mississippi, Nebraska, and North Carolina, as well as cotton growers in Mississippi and North Carolina, were surveyed about their views on changes in problematic weeds and weed pressure in cropping systems based on a glyphosate-resistant (GR) crop. No growers using a GR cropping system for more than 5 yr reported heavy weed pressure. Over all cropping systems investigated (continuous GR soybean, continuous GR cotton, GR corn/GR soybean, GR soybean/non-GR crop, and GR corn/non-GR crop), 0 to 7% of survey respondents reported greater weed pressure after implementing rotations using GR crops, whereas 31 to 57% felt weed pressure was similar and 36 to 70% indicated that weed pressure was less. Pigweed, morningglory, johnsongrass, ragweed, foxtail, and velvetleaf were mentioned as their most problematic weeds, depending on the state and cropping system. Systems using GR crops improved weed management compared with the technologies used before the adoption of GR crops. However, the long-term success of managing problematic weeds in GR cropping systems will require the development of multifaceted integrated weed management programs that include glyphosate as well as other weed management tactics.