• Authors:
    • Tetu, T.
    • Lea, P. J.
    • Dubois, F.
    • Hirel, B.
  • Source: Sustainability
  • Volume: 3
  • Issue: 9
  • Year: 2011
  • Summary: In this review, we present the recent developments and future prospects of improving nitrogen use efficiency (NUE) in crops using various complementary approaches. These include conventional breeding and molecular genetics, in addition to alternative farming techniques based on no-till continuous cover cropping cultures and/or organic nitrogen (N) nutrition. Whatever the mode of N fertilization, an increased knowledge of the mechanisms controlling plant N economy is essential for improving NUE and for reducing excessive input of fertilizers, while maintaining an acceptable yield and sufficient profit margin for the farmers. Using plants grown under agronomic conditions, with different tillage conditions, in pure or associated cultures, at low and high N mineral fertilizer input, or using organic fertilization, it is now possible to develop further whole plant agronomic and physiological studies. These can be combined with gene, protein and metabolite profiling to build up a comprehensive picture depicting the different steps of N uptake, assimilation and recycling to produce either biomass in vegetative organs or proteins in storage organs. We provide a critical overview as to how our understanding of the agro-ecophysiological, physiological and molecular controls of N assimilation in crops, under varying environmental conditions, has been improved. We have used combined approaches, based on agronomic studies, whole plant physiology, quantitative genetics, forward and reverse genetics and the emerging systems biology. Long-term sustainability may require a gradual transition from synthetic N inputs to legume-based crop rotation, including continuous cover cropping systems, where these may be possible in certain areas of the world, depending on climatic conditions. Current knowledge and prospects for future agronomic development and application for breeding crops adapted to lower mineral fertilizer input and to alternative farming techniques are explored, whilst taking into account the constraints of both the current world economic situation and the environment.
  • Authors:
    • Kutcher, H. R.
    • Johnston, A. M.
    • Bailey, K. L.
    • Malhi, S. S.
  • Source: Field Crops Research
  • Volume: 124
  • Issue: 2
  • Year: 2011
  • Summary: The impact of tillage system, rotation sequence and foliar fungicides on diseases and seed yield and quality of wheat, barley, pea, canola and flax was determined in the second cycle of three, 4-year rotations from 1998 to 2001 on a Black Chernozem (Udic Boroll) at Melfort, Saskatchewan, Canada. The objective of the study was to evaluate the impact of reduced-tillage production systems, broadleaf cropping intensity and fungicide use on cereal, oilseed and pulse crops in northeastern Saskatchewan, a sub-humid region of the northern Great Plains. A split-split plot design was used with three tillage systems (conventional, minimum and no-till) as main plots, three rotations of increasing broadleaf crop intensity (1. canola-wheat-barley-barley; 2. canola-barley-pea-wheat; and 3. canola-pea-flax-barley) as sub-plots, and fungicide treatments (treated or untreated) as sub-sub-plots. Fungicides appropriate for the diseases of concern were applied at recommended crop development stages and application rates, followed by assessment of diseases. Tillage system had little impact on diseases of any crop, although seed yield was usually greater under no-till for most crops under dry conditions. Rotation was not a major factor in disease severity of most of the crops, except barley in the rotation where it was grown for two consecutive years. Under dry conditions, barley yield was reduced when it followed flax compared with other crops, most likely due to less available soil moisture after flax. Fungicide application had the greatest impact on disease control and seed yield increase, although results varied among crops and years. In conclusion, the findings indicate that tillage system had little effect on disease severity, rotation contributed to greater disease severity only when a crop was grown intensively, such as on its own stubble, and fungicide application had variable effects on both disease control and seed yield.
  • Authors:
    • Lal, R.
  • Source: Food Policy
  • Volume: 36
  • Issue: S1
  • Year: 2011
  • Summary: Soils of the world's agroecosystems (croplands, grazing lands, rangelands) are depleted of their soil organic carbon (SOC) pool by 25-75% depending on climate, soil type, and historic management. The magnitude of loss may be 10 to 50 tons C/ha. Soils with severe depletion of their SOC pool have low agronomic yield and low use efficiency of added input. Conversion to a restorative land use and adoption of recommended management practices, can enhance the SOC pool, improve soil quality, increase agronomic productivity, advance global food security, enhance soil resilience to adapt to extreme climatic events, and mitigate climate change by off-setting fossil fuel emissions. The technical potential of carbon (C) sequestration in soils of the agroecosystems is 1.2-3.1 billion tons C/yr. Improvement in soil quality, by increase in the SOC pool of 1 ton C/ha/yr in the root zone, can increase annual food production in developing countries by 24-32 million tons of food grains and 6-10 million tons of roots and tubers. The strategy is to create positive soil C and nutrient budgets through adoption of no-till farming with mulch, use of cover crops, integrated nutrient management including biofertilizers, water conservation, and harvesting, and improving soil structure and tilth.
  • Authors:
    • Lewis, D. B.
    • Kaye, J. P.
    • Jabbour, R.
    • Barbercheck, M. E.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 26
  • Issue: 4
  • Year: 2011
  • Summary: Weed management is one of the primary challenges for producers transitioning from conventional to organic agriculture. Tillage and the use of cover crops are two weed control tactics available to farmers transitioning to organic management, but little is known about their interactive effects on soil quality during the transition period. We investigated the response of soils to tillage and initial cover crop during the 3-year transition to organic in a cover crop-soybean ( Glycine max)-maize ( Zea mays) rotation in the Mid-Atlantic region of the USA. The tillage treatment contrasted full, inversion tillage with moldboard plowing (FT) versus reduced tillage with chisel plowing (RT). The cover crop treatment contrasted annual versus mostly perennial species during the first year of the rotation. The experiment was initiated twice (Start 1 and Start 2), in consecutive years in adjacent fields. By the end of the experiment, labile carbon, electrical conductivity, pH and soil moisture were all greater under RT than under FT in both starts. Soil organic matter and several other soil attributes were greater under RT than under FT in Start 1, but not in Start 2, perhaps owing to differences between starts in initial field conditions and realized weather. Soil attributes did not differ between the two cover crop treatments. Combining our soils results with agronomic and economic analyses on these plots suggests that using RT during the organic transition can increase soil quality without compromising yield and profitability.
  • Authors:
    • Liu, K.
    • Wiatrak, P.
  • Source: International Journal of Plant Production
  • Volume: 5
  • Issue: 4
  • Year: 2011
  • Summary: Nitrogen (N) application management needs to be refined for low yielding environments under dryland conditions. This 3-yr study examined nitrogen fertilization management effects on corn ( Zea mays L.) plant characteristics and grain yield in rain fed environment under conventional tillage system. Nitrogen fertilization management consisted of two timing methods of N application [all N at planting and as split with 35 kg N ha -1 applied at planting and remaining N applied at vegetative (V) 6 growth stage] and five N rates (0, 45, 90, 135, and 180 kg N ha -1). Insufficient rainfall at reproductive stage in 2008 and 2009 likely resulted in significant reduction of grain yield compared with grain yield in 2007, average 2.9 vs. 5.9 Mg ha -1. Grain yield increased with N application up to 45 kg ha -1; however, no further increase in N application resulted in increased yields. Plant height, ear height, relative chlorophyll (SPAD) content, and normalized difference vegetation index (NDVI) at reproductive (R 1) stage increased with increasing N rate up to 90, 90, 135, and 90 kg N ha -1, respectively. Corn grain yield significantly correlated with plant height at R 1, SPAD at V 8, NDVI and LAI at V 8 and R 1 stage. The combination of plant height, NDVI, and LAI of R 1 stage explained most of the variability of grain yield (r-square=0.71). The fertilization timing had no effect on corn grain yield and plant characteristics. These observations showed that applying more than 45 kg N ha -1 to corn under dryland conditions with insufficient rainfall, especially during corn pollination, may not significantly increase grain yields.
  • Authors:
    • Pozo, A. del
    • Martinez G.,I.
    • Prat, C.
    • Uribe, H.
    • Valderrama V., N.
    • Zagal, E.
    • Sandoval, M.
    • Fernandez, F.
    • Ovalle, C.
  • Source: Chilean Journal of Agricultural Research
  • Volume: 71
  • Issue: 4
  • Year: 2011
  • Summary: Chilean dryland areas of the Mediterranean climate region are characterized by highly degraded and compacted soils, which require the use of conservation tillage systems to mitigate water erosion as well as to improve soil water storage. An oat ( Avena sativa L. cv. Supernova-INIA) - wheat ( Triticum aestivum L. cv. Pandora-INIA) crop rotation was established under the following conservation systems: no tillage (Nt), Nt+contour plowing (Nt+Cp), Nt+barrier hedge (Nt+Bh), and Nt+subsoiling (Nt+Sb), compared to conventional tillage (Ct) to evaluate their influence on soil water content (SWC) in the profile (10 to 110 cm depth), the soil compaction and their interaction with the crop yield. Experimental plots were established in 2007 and lasted 3 yr till 2009 in a compacted Alfisol. At the end of the growing seasons, SWC was reduced by 44 to 51% in conservation tillage systems and 60% in Ct. Soil water content had a significant (p<0.05) interaction with tillage system and depth; Nt+Sb showed lower SWC between 10 to 30 cm, but higher and similar to the rest between 50 to 110 cm except for Ct. Although, SWC was higher in conservation tillage systems, the high values on soil compaction affected yield. No tillage+subsoiling reduced soil compaction and had a significant increment of grain yield (similar to Ct in seasons 2008 and 2009). These findings show us that the choice of conservation tillage in compacted soils of the Mediterranean region needs to improve soil structure to obtain higher yields and increment SWC.
  • Authors:
    • Wood,C. W.
    • Price,A. J.
    • Mulvaney,M. J.
  • Source: Journal of Sustainable Agriculture
  • Volume: 35
  • Issue: 3
  • Year: 2011
  • Summary: Limited input producers may adopt no-till production if sufficient weed suppression can be achieved. High-biomass producing cover crops used in conjunction with organic mulches may provide sufficient weed control in no-till vegetable production. Our objective was to quantify weed suppression from a forage soybean summer cover crop and three types of organic mulches applied after collard ( Brassica oleracea L.) planting. Forage soybean residue did not suppress weeds, but mulches were generally effective. Broadleaf and sedge weeds decreased in population size over the three-year period, but grass weed management remained problematic until three years after conversion to no-till. Grass suppression was greater when mulches were applied after the first year. Collard yield, averaging 17,863 kg ha -1, was not affected by any cover crop or mulch treatment.
  • Authors:
    • Petersen, S. O.
    • Mutegi, J. K.
    • Hansen, E. M.
    • Munkholm, L. J.
  • Source: Soil Biology and Biochemistry
  • Volume: 43
  • Issue: 7
  • Year: 2011
  • Summary: Conservation tillage practices are widely used to protect against soil erosion and soil C losses, whereas winter cover crops are used mainly to protect against N losses during autumn and winter. For the greenhouse gas balance of a cropping system the effect of reduced tillage and cover crops on N2O emissions may be more important than the effect on soil C. This study monitored emissions of N2O between September 2008 and May 2009 in three tillage treatments, i.e., conventional tillage (CT), reduced tillage (RI) and direct drilling (DD), all with (+CC) or without (-CC) fodder radish as a winter cover crop. Cover crop growth, soil mineral N dynamics, and other soil characteristics were recorded. Furthermore, soil concentrations of N2O were determined eight times during the monitoring period using permanently installed needles. There was little evidence for effects of the cover crop on soil mineral N. Following spring tillage and slurry application soil mineral N was dominated by the input from slurry. Nitrous oxide emissions during autumn, winter and early spring remained low, although higher emissions from +CC treatments were indicated after freezing events. Following spring tillage and slurry application by direct injection N2O emissions were stimulated in all tillage treatments, reaching 250-400 mu g N m(-2) h(-1) except in the CT + CC treatment, where emissions peaked at 900 mu g N M-2 h(-1). Accumulated emissions ranged from 1.6 to 3.9 kg N2O ha(-1). A strong positive interaction between cover crop and tillage was observed. Soil concentration profiles of N2O showed a significant accumulation of N2O in CT relative to RI and DD treatments after spring tillage and slurry application, and a positive interaction between slurry and cover crop residues. A comparison in early May of N2O emissions with flux estimates based on soil concentration profiles indicated that much of the N2O emitted was produced near the soil surface.
  • Authors:
    • Labreuche, J.
    • Richard, G.
    • Roger-Estrade, J.
  • Source: Cahiers Agricultures
  • Volume: 20
  • Issue: 3
  • Year: 2011
  • Summary: In this paper, we present a review of the literature on the effects of no-ploughing on soil structure, porosity and stability. In the second part, we discuss the consequences on soil erosion in a temperate environment. The effect of reduced tillage on soil physical properties has firstly to be evaluated on soil structure. If carbon accumulation on the soil surface improves aggregate stability, no-ploughing also greatly affects soil porosity. Not only does it decrease during the period following adoption of no-ploughing, but it also changes in nature and connectivity due to weathering, roots and biological activity. However, the efficiency of these factors is site-dependent and varies with the duration of no-ploughing and the crop sequence. Under tropical climates, reduced tillage systems have been proposed to prevent soil erosion while in temperate areas the present increase of no-till is motivated firstly by the decrease of production and mechanization costs. However, the efficiency of the numerous no-plough tillage systems on erosion control is not systematic. The soil must be sufficiently covered by crop residues and the infiltration rate has to remain high enough. This note critically assesses the available results on these two aspects of the effect of reduced tillage on soil physics.
  • Authors:
    • Bahrami, H.
    • Roozbeh, M.
    • Sheikhdavoodi, M. J.
    • Almassi, M.
  • Source: African Journal of Agricultural Research
  • Volume: 6
  • Issue: 23
  • Year: 2011
  • Summary: Degradation of agricultural soils and nutrient losses affected by intensive agriculture and tillage is of environmental and agricultural concerns. These concerns lead to emergence and development of conservative technologies such as conservation tillage systems [reduced tillage (RT) and no-till (NT)] and anionic polyacrylamide (PAM). A study was done in order to investigate the interactive effects of three tillage systems and three PAM concentration on sediment loss, runoff nitrate concentration, nitrogen losses from the soil-plant system and nitrogen recovery. The experimental design was a randomized complete block with split-plot arranged in three replications. The anionic polyacrylamide (PAM) were in three levels of zero (P0), 10 (P10) and 20 (P20) mg L -1 as the main plot and different tillage intensities as the subplot including moldboard plowing plus two disk harrow passes (CT1), one stubble cultivator pass (RT) and moldboard plowing plus one power harrow pass (CT2). The RT treatment relative to CT2 led to soil loss reduction by 23.56% during the first irrigation. The P10 and P20 treatments relative to P0, caused sediment concentration reduction by 98.1 and 98.09% and soil loss reduction by 98.7% and 98.8%, respectively. The RT * P20 treatment had a greater impact in reduction runoff nitrate losses than CT1 * P20 and CT2 * P20 treatments. Losses of N in the fertilized plots and recovery of applied N (RAN) was influenced by both tillage system and PAM application.