• Authors:
    • Clay, D. E.
    • Carlson, C. G.
    • Clay, S. A.
    • Reicks, G.
    • Kim, K.
    • Mamani-Pati, F.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 6
  • Year: 2010
  • Summary: The harvesting of plant biomass in excess of the soil organic carbon (SOC) maintenance requirement can produce short-term economic benefits at the cost of long-term sustainability. The objective of this study was to assess the impact of corn ( Zea mays L.) harvesting approach, N rate, and simulated landscape positions on estimated long-term SOC maintenance, profitability, and the energy efficiency of no-till corn grown in eastern South Dakota. The 3-yr experiment (2002-2004) contained four N rates (0, 56, 112, and 168 kg N ha -1), two simulated landscape positions (shoulder and backslope), and two harvesting methods (grain with 100% stover returned or grain+40% corn stover returned). No-tillage was used at the site. Energy gains (out-input), for a cropping system where corn grain or corn grain plus stover was sold for ethanol production, were calculated. Profitability was estimated and SOC turnover was simulated using the annual time-step model, SOC t=SOC t-1+k NHCNHC-k soc SOC t-1, where SOC t was SOC at time t, SOC t-1 was SOC at the sampling date before time t, k NHC was rate that nonharvested carbon (NHC) was converted to SOC, and k soc was the rate that SOC was converted to CO 2 Tillage impacts on k SOC was estimated with the model k soc [g SOC-C (g SOC year) -1]=0.0115+0.00631(tillage events). When only grain was harvested, the highest and lowest energy gains and financial were associated with the 112 kg N ha -1 (46.6 GJ ha -1 and $427 ha -1) and the 0 kg N per ha -1 (37.5 GJ ha -1 and $192 ha -1) treatments, respectively. Applying more than 112 kg N ha -1 did not increase energy gains or financial returns. Profits were increased by 60% when corn stover was harvested for ethanol production and lower yielding simulated shoulder/summit position had a lower energy gain (59.3 GJ ha -1 and $425 ha -1) and financial return than the backslope position (66.3 GJ ha -1 and $614 ha -1). The SOC sustainability analysis suggests that the ability of a system to maintain SOC depends on many factors including the amount of nonharvested carbon returned to the site, and the amount of carbon contained in the soil.
  • Authors:
    • Wilson, D.
    • Mischler, R.
    • Duiker, S. W.
    • Curran, W. S.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 1
  • Year: 2010
  • Summary: Rolling-crimping to control hairy vetch ( Vicia villosa Roth) may make organic no-till corn ( Zea mays L.) possible. This study investigated how rolling-crimping date and growth stage of the cover crop affected hairy vetch control and if a rolled-crimped hairy vetch cover crop could supply weed control for no-till corn. Hairy vetch was planted in late August and was rolled and crimped and planted to corn at four dates ("planting dates") between late May and late June at three Pennsylvania locations. Hairy vetch biomass, measured at each planting date, varied from 2000 to 8000 kg ha -1. Hairy vetch control with the roller-crimper varied through the flowering stage and was consistent after early pod set. The hairy vetch cover crop reduced weed density by at least 50%, with annual weeds being affected more than perennials. Total weed biomass was reduced 31, 93, and 94% in different site-years compared with no-cover plots. As corn planting dates were delayed, greater amounts of vetch mulch and lower weed density helped reduce weed biomass. Corn yields in the organic no-till system with a hairy vetch cover crop ranged from 1.1 Mg ha -1 to 9.6 Mg ha -1. Low yields were attributed to incomplete control of hairy vetch, weed competition, reduced corn plant populations, increased insect pests, and possibly inadequate N supply. This study shows that it is possible to kill hairy vetch with a roller-crimper and provide weed control for organic corn, resulting in reasonable corn yields, but that production risk increases.
  • Authors:
    • Qin, L.
    • Shuang, L.
    • Wenquing, H.
    • Xurong, M.
    • Hoogenboom, G.
    • Changrong, Y.
    • Jiantao, D.
    • Ahmad, M.
    • Nangia, V.
  • Source: International Journal of Agricultural and Biological Engineering
  • Volume: 3
  • Issue: 2
  • Year: 2010
  • Summary: In the dryland regions of North China, water is the limiting factor for rainfed crop production. Conservation agriculture (featuring reduced or zero tillage, mulching, crop rotations and cover crops) has been proposed to improve soil and water conservation and enhance yields in these areas. Conservation agriculture systems typically result in increased crop water availability and agro-ecosystem productivity, and reduced soil erosion. To evaluate the potential of conservation agriculture to improve soil water balance and agricultural productivity, the DSSAT crop model was calibrated using the data of a field experiment in Shouyang County in the semi-arid northeastern part of the Yellow River Basin. The average annual precipitation at the site is 472 mm, 75% of which falls during the growing season. The site had a maize-fallow-maize rotation, data from two crop seasons (2005 and 2006) and four treatments for calibration and analysis were used. The treatments were: conventional tillage (CT), no-till with straw mulching (NTSM), all-straw incorporated (ASRT) and one-third residue left on the surface with no-till (RRT). The calibration results gave satisfactory agreement between field observed and model predicted values for crop yield for all treatments except RRT treatment, and for soil water content of different layers in the 150 cm soil profile for all treatments. The difference between observed and predicted values was in the range of 3%-25% for maize yield and RMSE was in the range of 0.03-0.06 cm 3/cm 3 for soil water content measured periodically each cropping season. While these results are encouraging, more rigorous calibration and independent model evaluation are warranted prior to making recommendations based on model simulations. Medium-term simulations (1995-2004) were conducted for three of the treatments using the calibrated model. The NTSM and ASRT treatments had similar or higher yields (by up to 36%), higher crop water productivity by up to 28% and reduced runoff of up to 93% or 43 mm compared to CT treatment.
  • Authors:
    • Newman, J. K.
    • Laflen, J. M.
    • Kaleita, A. L.
  • Source: Journal of Soil and Water Conservation
  • Volume: 65
  • Issue: 4
  • Year: 2010
  • Summary: Corn stover is promoted as a readily available feedstock for cellulosic ethanol fermentation, potentially adding value to Iowa's corn harvest. However, soil productivity and water quality could be adversely affected by poor residue management practices. This paper presents the results of computer simulations of soil erosion by water under various corn stover harvesting and management scenarios applied universally across the state of Iowa. The WEPP (Water Erosion Prediction Project) computer model was used to simulate soil loss in Iowa at 17,848 agricultural point locations of the 1997 National Resources Inventory. Location information at the township level of 9.66 by 9.66 km (6 by 6 mi) for the National Resources Inventory points allows for presentation of results in the form of gridded color-scale maps. The maps indicate corn stover removal risk at the following levels: extreme, high, medium, or low. Risk categories are based on the soil loss tolerance (T) and 1/2 T as constraints. This paper presents simulated impacts of corn stover removal on soil erosion only. Important considerations for maintaining soil organic carbon are reviewed and discussed. The simulation results suggest that the amount of harvestable corn stover is not uniform in Iowa when water erosion control guides management. No-till is necessary to maintain soil loss below permissible levels of T and 1/2T in regions with steeper slopes. Maps and corresponding analyses in this paper help guide policy pertaining to the harvest of corn stover in Iowa.
  • Authors:
    • Encide-Olibone,A. P.
    • Olibone,D.
    • Rosolem,C. A.
  • Source: Soil Use and Management
  • Volume: 26
  • Issue: 4
  • Year: 2010
  • Summary: Crop rotation and the maintenance of plant residues over the soil can increase soil water storage capacity. Root access to water and nutrients depends on soil physical characteristics that may be expressed in the Least Limiting Water Range (LLWR) concept. In this work, the effects of crop rotation and chiselling on the soil LLWR to a depth of 0.1 m and crop yields under no-till were studied on a tropical Alfisol in Sao Paulo state, Brazil, for 3 yr. Soybean and corn were grown in the summer in rotation with pearl millet (Pennisetum glaucum, Linneu, cv. ADR 300), grain sorghum (Sorghum bicolor, L., Moench), congo grass (Brachiaria ruziziensis, Germain et Evrard) and castor bean (Ricinus comunis, Linneu) during fall/winter and spring, under no-till or chiselling. The LLWR was determined right after the desiccation of the cover crops and before soybean planting. Soil physico-hydraulic conditions were improved in the uppermost soil layers by crop rotations under zero tillage, without initial chiselling, from the second year and on, resulting in soil quality similar to that obtained with chiselling. In seasons without severe water shortage, crop yields were not limited by soil compaction, however, in a drier season, the rotation with congo grass alone or intercropped with castor resulted in the greatest cover crop dry matter yield. Soybean yields did not respond to modifications in the LLWR.
  • Authors:
    • Leroux, X.
    • Attard, E.
    • Lemaire, G.
    • Laurent, F.
    • Chabbi, A.
    • Nicolardot, B.
    • Poly, F.
    • Recous, S.
  • Source: Proceedings of the 19th World Congress of Soil Science: Soil solutions for a changing world, Brisbane, Australia
  • Year: 2010
  • Summary: The COSMOS-Flux project aimed at studying two situations that have important environmental impacts at a larger scale : the conversion tillage no tillage where different tillage systems have been applied for 14 years at the start of experiment; the conversion grassland annual crop where the introduction of temporary grassland into rotations is studied. The characterization of upper layers of soil for C and N pools, mineralization, immobilization and nitrification of N, along with characteristics of the nitrifying and denitrifying bacterial communities (activity, size and structure) were followed during 18 to 36 months after conversion. We observed that the tillage of soils untilled for 14 years, or the ploughing of the 5-year old grassland were major disturbances for the soils, which led to a very fast evolution of soil organic matter pools, N fluxes and microbial activities towards the characteristics observed for tilled and arable situations. Conversely, the shifts from till to no-till, and the establishment of grassland on soil previously cropped with annual species did not change significantly their soil characteristics at the time scale of the study. Among soil environmental variables, soil organic carbon appeared as a key driver of the observed responses.
  • Authors:
    • Rensburg, L. D. van
  • Source: South African Journal of Plant and Soil
  • Volume: 27
  • Issue: 1
  • Year: 2010
  • Summary: This is the third soil physics review to be published in South African Journal of Plant and Soil. In the previous reviews the focus was broad and covered almost every aspect of the subject, providing a comprehensive list of contributions in soil physics. For the 25th year anniversary celebration of South African Journal of Plant and Soil, I have chosen to narrow the scope and focus on advances in soil physics in relation to irrigation and dryland agriculture. From a bio-physical viewpoint, South African researchers have made a major contribution to the body of scientific knowledge about irrigation and its application, expressed mainly in the form of irrigation or crop models such as PUTU, SWB and BEWAB. Attention was also given to modern ways of irrigation scheduling based on continuous soil water monitoring. Several irrigation scheduling service providers have adapted their businesses accordingly, with the result that South Africa is probably the leading country in Africa with respect to soil water monitoring and associated communication technology. In contrast, the review has shown that at farm and irrigation scheme level, salt management requires urgent attention. This is necessary as a precautionary measure to protect our natural resources. In the second part of the review the contribution of soil physics in relation to tillage practices is explored, and in particular how these have modified the field water balance components in order to enhance yield and rain water productivity. Based on the results of field experiments, new relationships were established, viz. rainfall and maize yield; water storage and yield; runoff and surface coverage by crop residue mulches; tillage depth, texture and yield relationships. Lastly, the review also showed how the water balance on clay and duplex soils in semi-arid zones can be modified through in-field rainwater harvesting to increase their rain water productivity. This technology has enhanced the livelihoods of many communal families who have applied the technique in their homesteads.
  • Authors:
    • Huon, S.
    • Soulileuth, B.
    • Jouquet, P.
    • Pierret, A.
    • Ribolzi, O.
    • Valentin, C.
    • Bourdon, E.
    • Chantharath, B.
    • Rouw, A. de
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 136
  • Issue: 1-2
  • Year: 2010
  • Summary: There is limited information, particularly in the tropics, of farming systems that loose or accumulate carbon in their soils. We compared no-till with a mulch-providing cover crop with conventional tillage without cover crop. Side effects were also investigated, weeds, surface crusting, soil macrofauna, infiltration, porosity and roots. The study site was a flat sandy clay loam. Treatments were maintained over five years; within this period, the time between the first and last soil sampling was exactly four years. Both times the same profile locations and exactly the same depths were sampled thereby greatly reducing inherent soil variability. Soil was sampled at five increments from 0 to 40 cm depth. The biomass contributions of maize, cover crop and weeds were measured. The main findings were: (1) The cover crop that was alleged to supply extra inputs to the no-till system failed to do so because the weeds in the tillage treatment became as efficient in accumulating biomass as the planted cover crop. (2) With equal organic inputs over four years (43.0 Mg dry weight ha -1 incorporated into the soil under conventional tillage, and 44.2 Mg dry weight ha -1 remaining on the soil surface as mulch under no-till), the tillage system stored (0-40 cm) significantly soil carbon (+590 g C m -2), whereas the no-till lost carbon (-133 g C m -2). The difference between the systems was significant. Carbon accumulated just below the plough layer. Nitrogen stocks remained unchanged. A very significant lowering of the C:N ratio occurred under no-till. The process of transforming the available biomass on the soil surface into organic matter is apparently too slow to avoid direct losses under no-till. Alternatively, ploughing plant residues into the soil enables to capture some of what would otherwise be lost as CO 2 through decay, thereby increasing soil carbon. (3) In the last three years of the experiment, maize grain yields and crop residues stabilized at a lower level but were significantly higher under no-till, 16% and 34%, respectively. Higher yields were attributed to more soil water under no-till due to improved soil structure, though bulk density was not affected. The mulch layer protecting the soil surface favoured infiltration by keeping it crust-free. Water availability was further promoted by a better connectivity of pores and more macrofauna. However, the no-till system depended heavily on fertilizers and herbicides. The lack of effectiveness of herbicides against shifting weed communities threatens the continuation of the system.
  • Authors:
    • Sandor, M.
    • Domuta, C.
    • Vuscan, A.
    • Domuta, C.
    • Samuel, A.
  • Source: Research Journal of Agricultural Science
  • Volume: 42
  • Issue: 3
  • Year: 2010
  • Summary: The importance of phosphatase for plant nutrition has repeatedly been pointed out. In most soils, the organically bound P-fraction is higher than the inorganic. Phosphorus uptake by plants requires mineralization of the organic P-component by phosphatases to orthophosphate. Phosphatases are inducible enzymes that are produced predominantly under conditions of low phosphorus availability. Phosphatases are excreted by plant roots and by microorganisms. Microbial phosphatases dominate in soils. The phosphomonoesterases, so-called phosphatases differ in their substrate specificity and their pH optimum. One can thus differentiate between acid and alkaline phosphatases in the soil. Phosphatase activities were determined in the 0-20-, 20-40- and 40-60-cm layers of a preluvosoil submitted to a complex tillage (no-till and conventional tillage), crop rotation (2- and 3-crop rotations) and fertilisation [mineral(NP) fertilisation and farmyard-manuring] experiment. It was found that the activities decreased in the order: acid phosphatase activity > alkaline phosphatase activity. Each activity decreased with increasing sampling depth. No-till-in comparison with conventional tillage - resulted in significantly higher soil phosphatase activities in the 0-20-cm layer and in significantly lower activities in the deeper layers. The soil under maize or wheat was more phosphatase-active in the 3- than in the 2-crop rotation. In the 2-crop rotation higher soil phosphatase activities were recorded under wheat than under maize. Farmyard-manuring of maize - in comparison with its mineral fertilisation - led to a significant increase in each activity.
  • Authors:
    • Sandhya, V.
    • Ali, S. Z.
    • Grover, M.
    • Reddy, G.
    • Venkateswarlu, B.
  • Source: Plant Growth Regulation
  • Volume: 62
  • Issue: 1
  • Year: 2010
  • Summary: Drought is one of the major abiotic stresses affecting yield of dryland crops. Rhizobacterial populations of stressed soils are adapted and tolerant to stress and can be screened for isolation of efficient stress adaptive/tolerant, plant growth promoting rhizobacterial (PGPR) strains that can be used as inoculants for crops grown in stressed ecosystems. The effect of inoculation of five drought tolerant plant growth promoting Pseudomonas spp. strains namely P. entomophila strain BV-P13, P. stutzeri strain GRFHAP-P14, P. putida strain GAP-P45, P. syringae strain GRFHYTP52, and P. monteilli strain WAPP53 on growth, osmoregulation and antioxidant status of maize seedlings under drought stress conditions was investigated. Drought stress induced by withholding irrigation had drastic effects on growth of maize seedlings. However seed bacterization of maize with Pseudomonas spp. strains improved plant biomass, relative water content, leaf water potential, root adhering soil/root tissue ratio, aggregate stability and mean weight diameter and decreased leaf water loss. The inoculated plants showed higher levels of proline, sugars, free amino acids under drought stress. However protein and starch content was reduced under drought stress conditions. Inoculation decreased electrolyte leakage compared to uninoculated seedlings under drought stress. As compared to uninoculated seedlings, inoculated seedlings showed significantly lower activities of antioxidant enzymes, ascorbate peroxidase (APX), catalase (CAT), glutathione peroxidase (GPX) under drought stress, indicating that inoculated seedlings felt less stress as compared to uninoculated seedlings. The strain GAP-P45 was found to be the best in terms of influencing growth and biochemical and physiological status of the seedlings under drought stress. The study reports the potential of rhizobacteria in alleviating drought stress effects in maize.