• Authors:
    • Netland, J.
    • Brandsaeter, L. O.
    • Sjursen, H.
  • Source: Acta Agriculturae Scandinavica, Section B - Soil & Plant Science
  • Volume: 62
  • Issue: 2
  • Year: 2012
  • Summary: Cover crops can be used to reduce leaching and erosion, introduce variability into crop rotation and fix nitrogen (N) for use by the main crops, less is however known about effects on weeds. The effects on weed seed bank, weed growth and grain yield of 4 years of annual undersown clover and ryegrass alone and in combination, and one of the 4 years with clover or clover + grass as green manure, were studied in oat and spring wheat at two experimental sites in south-eastern Norway. These treatments were compared with no undersown crop (control) and with weed harrowing. In contrast to many results in the literature, the undersown clover in this study did not suppress annual weeds, but fertilized the weeds as well as the cereals. Undersown clover resulted in a statistically significant increase of grain yield at the two sites to 116% and 121% of control. During the 4-year period relative seed bank and density of emerged weed (dominated by Spergula arvensis) increased significantly about 4.5 and 10 times respectively in the undersown clover plots at Apelsvoll. At Kise both ryegrass alone and ryegrass mixed with clover significantly suppressed the weed biomass to 70% and 74% of control respectively. It is concluded that fertilization effects of undersown clover may have dominated and overriden the competitive effects. One whole-season clover green manure did not increase the mean yield, but resulted in a significant drop in seed bank size the following year, because of limited weed establishment in an established ley. Only a slight increase in average weed biomass was observed at one of the two experimental sites. The weed seed bank and the weed biomass were essentially kept at steady state during the experimental period in harrowed plots, but harrowing decreased grain yield significantly at both sites.
  • Authors:
    • Merckx, R.
    • Vanuytrecht, E.
    • Clymans, W.
    • Langhans, C.
    • Diels, J.
    • Govers, G.
    • Van den Putte, A.
    • Raes, D.
  • Source: Soil & Tillage Research
  • Volume: 122
  • Year: 2012
  • Summary: One of the most frequently used techniques to combat soil erosion on agricultural fields is conservation agriculture (CA). Conservation tillage techniques (CT), together with residue management and rotation are the pillars of CA. Studies have shown that CT can indeed be very effective in combating soil erosion. While several studies have demonstrated how CT may affect (the distribution of) carbon in the soil and documented compaction risks under CT, much less information is available with respect to the potential effects of CT on within-soil water movement and nutrient status. We therefore investigated the effect of superficial (0.15-0.2 m depth) and deep (0.3-0.4 m depth) CT on soil properties of agricultural silt loam soils in Belgium. From 2008 to 2010, we analyzed the effect of CT on water content, hydraulic conductivity, penetration resistance, bulk density, organic carbon and nitrate content of the soil. At the same time the effect of CT on root growth and crop yield was analyzed. We found that soil structural differences between conventional mouldboard ploughing and deep CT tended to be very small and did not have any effect on root growth and/or crop yield. Furthermore, we were not able to detect any significant difference between the different implements used in CT. The application of superficial CT however, led to an increase in penetration resistance in the upper soil layer hindering vertical soil water movement and root growth on one trial field. Crop yield was not affected due to a sufficient water and nutrient supply. Effects of deep CT on water availability and water movement were very limited and suggest that deep CT may slightly improve water availability only during dry summer periods. Total carbon content was not affected by CT, but its distribution through the plough layer changed whereby the carbon content in the upper few centimetres of soil increased while a decrease was noted at greater depths. The reduction of the nitrate content observed in deeper soil layers indicates that reduced tillage did not lead to increased nitrate leaching and may even help to reduce this problem if adequate catch crops are planted. We conclude that, on the Belgian silt loam soils, deep CT can be practiced whereby good soil functioning can be ensured. As crop yields were also similar, deep CT is a viable alternative that may contribute to soil protection. The use of superficial CT cannot be recommended due to a compaction risk. (c) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Satkus, A.
    • Velykis, A.
  • Source: Žemdirbystė (Agriculture)
  • Volume: 99
  • Issue: 1
  • Year: 2012
  • Summary: Research was done at the Joniskelis Experimental Station of the Lithuanian Research Centre for Agriculture and Forestry on a clay loam Endocalcari-Endohypogleyic Cambisol (CMg-n-w-can). The objective of this study was to determine the effects of reduced (shallow ploughing and ploughless tillage) tillage as well as its combinations with supplementary agronomic practices, improving soil conditions - incorporation of lime sludge, cover crop (mixture of white mustard and oilseed radish) for green manure and mulch on the emergence, growth and development of field pea (Pisum sativum L.) crop. Data revealed that shallow ploughing caused the worst field pea emergence in 2008. Ploughless tillage in combination with lime sludge incorporation resulted in a significantly higher soil water content in seedbed layer (0-5 cm) directly after field pea sowing in 2009, better field pea germination within the prolonged droughty post-sowing periods (18 and 20 days respectively in 2008 and 2009) and higher grain yield in 2008 as compared to deep ploughing. Due to the ploughless tillage together with incorporation of the cover crop biomass for the green manure late in autumn, significantly higher soil water content was registered in the seedbed directly after sowing in 2010 and at 5-15 cm depth according to the average data of 2008-2010; however the emergence and growth of field pea under droughty conditions were worse, and yield decreased in 2009 and 2010. Application of ploughless tillage with no supplementary practices resulted in significantly higher soil water content in seedbed directly after field pea sowing in 2010; however, in field pea yield decreased in 2009. Cover crop winter mulch without tillage in autumn led to a significantly higher soil water content in the seedbed directly after sowing in 2010, while the soil water content after field pea emergence at 5-15 cm depth in 2008 and at 15-25 cm depth according to the average data of 2008-2010 was lower, seedbed structure was mostly worse, field pea growth and development were poor and crop yield was lower in all years of study as compared to deep ploughing. Rapid capillary water movement, characteristic of clay loam with predominant silty fractions, could lead to a higher drying of soil layers unloosened in the autumn. Field pea yield was influenced by the amount of rainfall during one month after sowing in a droughty year 2008 and by the soil structure in a seedbed in 2009.
  • Authors:
    • Nichols ,R. L.
    • Webster, T. M.
  • Source: Weed Science
  • Volume: 60
  • Issue: 2
  • Year: 2012
  • Summary: Changes in the weed flora of cropping systems reflect the impacts of factors that create safe sites for weed establishment and facilitate the influx and losses to and from the soil seedbank. This analysis of the annual surveys of the Southern Weed Science Society documents changes in the weed flora of the 14 contiguous southern states since the advent of transgenic, herbicide-resistant crops. In 1994 and 2009, the top five weeds in corn were morningglories, Texas millet, broadleaf signalgrass, johnsongrass, and sicklepod; in this same period Palmer amaranth, smartweeds, and goosegrass had the greatest increases in importance in corn. In cotton, morningglories and nutsedges were among the top five most troublesome weeds in 1995 and 2009. Palmer amaranth, pigweeds, and Florida pusley were also among the five most troublesome species in 2009; the weeds with the largest increases in importance in cotton were common ragweed and two species with tolerance to glyphosate, Benghal dayflower and Florida pusley. In soybean, morningglories, nutsedges, and sicklepod were among the top five weed species in 1995 and 2009. Two species with glyphosate resistance, Palmer amaranth and horseweed, were the second and fourth most troublesome weeds of soybean in 2009. In wheat, the top four weeds in 2008 were the same as those in 1994 and included Italian ryegrass, wild garlic, wild radish, and henbit. Crop production in the southern region is a mosaic of various crop rotations, soil types, and types of tillage. During the interval between the surveys, the predominant change in weed management practices in the region and the nation was the onset and rapid dominance of the use of glyphosate in herbicide-resistant cultivars of corn, cotton, and soybean. Because of the correspondence between the effects of glyphosate on the respective weed species and the observed changes in the weed flora of the crops, it is likely the very broad use of glyphosate was a key component shaping the changes in weed flora. Only eight of the top 15 most troublesome weeds of cotton and soybean, the crops with the greatest use of glyphosate, were the same in 1995 and 2009. In contrast, in corn and wheat where adoption of glyphosate-resistant cultivars lags or is absent, 12 of the 15 most troublesome weeds were the same in 1994 and 2008. These findings show on a regional scale that weeds adapt to recurrent selection from herbicides, currently the predominant weed management tool. Future research should seek methods to hinder the rapid spread of herbicide-tolerant and evolution of herbicide-resistant weed species. As new tools are developed, research should focus on ways to preserve the efficacy of those tools through improved stewardship. Nomenclature: annual bluegrass, Poa annua L. POAAN; Benghal dayflower, Commelina benghalensis L. COMBE; broadleaf signalgrass, Urochloa platyphylla (Nash) R.D. Webster BRAPP; common ragweed, Ambrosia artemisiifolia L. AMBEL; Florida pusley Richardia scabra L. RCHSC; goosegrass Eleusine indica (L.) Gaertn. ELEIN; groundcherries, Physalis spp.; henbit, Lamium amplexicaule L. LAMAM; horseweed, Conyza canadensis (L.) Cronq. ERICA; Italian ryegrass, Lolium perenne L. ssp. multiflorum (Lam.) Husnot LOLMU; johnsongrass, Sorghum halepense (L.) Pers. SORHA; morningglories, Ipomoea spp.; nutsedges, Cyperus spp.; Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA; pigweed, Amaranthus spp.; sicklepod, Senna obtusifolia (L.) H.S. Irwin & Barneby CASOB; smartweeds, Polygonum spp.; Texas millet, Urochloa texana (Buckl.) R. Webster PANTE; wild garlic, Allium vineale L. ALLVI; wild radish, Raphanus raphanistrum L. RAPRA; corn, Zea mays L.; cotton, Gossypium hirsutum L.; soybean Glycine max. (L.) Merr.; wheat, Triticum aestivum L.
  • Authors:
    • Zhang, X. Y.
    • Studdert, G.
    • Morras, H.
    • Huffman, T.
    • Duran, A.
    • Kravchenko, Y. S.
    • Burras, C. L.
    • Liu, X. B.
    • Cruse, R. M.
    • Yuan, X. H.
  • Source: Canadian Soil Science
  • Volume: 92
  • Issue: 3
  • Year: 2012
  • Summary: Mollisols - a.k.a., Black Soils or Prairie Soils - make up about 916 million ha, which is 7% of the world's ice-free land surface. Their distribution strongly correlates with native prairie ecosystems, but is not limited to them. They are most prevalent in the mid-latitudes of North America, Eurasia, and South America. In North America, they cover 200 million ha of the United States, more than 40 million ha of Canada and 50 million ha of Mexico. Across Eurasia they cover around 450 million ha, extending from the western 148 million ha in southern Russia and 34 million ha in Ukraine to the eastern 35 million ha in northeast China. They are common to South America's Argentina and Uruguay, covering about 89 million and 13 million ha, respectively. Mollisols are often recognized as inherently productive and fertile soils. They are extensively and intensively farmed, and increasingly dedicated to cereals production, which needs significant inputs of fertilizers and tillage. Mollisols are also important soils in pasture, range and forage systems. Thus, it is not surprising that these soils are prone to soil erosion, dehumification (loss of stable aggregates and organic matter) and are suffering from anthropogenic soil acidity. Therefore, soil scientists from all of the world's Mollisols regions are concerned about the sustainability of some of current trends in land use and agricultural practices. These same scientists recommend increasing the acreage under minimum or restricted tillage, returning plant residues and adding organic amendments such as animal manure to maintain or increase soil organic matter content, and more systematic use of chemical amendments such as agricultural limestone to replenish soil calcium reserves.
  • Authors:
    • Du Preez, C. C.
    • Kotze, E.
    • Loke, P. F.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 94
  • Issue: 1
  • Year: 2012
  • Summary: Soil organic matter (SOM) degradation is common in semi-arid regions due to frequent and intensive cultivation, removal of crop residues after harvesting and warmer environmental conditions. Therefore, we evaluated the effects of long-term wheat production management practices on organic matter content of a Plinthosol in semi-arid South Africa. The treatments included two methods of straw management (unburned and burned), three methods of tillage (no-tillage, stubble mulch and ploughing) and two methods of weeding (chemical and mechanical). Soil samples were collected in 2010 at various depths and analysed for soil organic carbon (SOC), soil total nitrogen (STN) and soil total sulfur (STS) as organic matter indices. Treatments where straw was not burned had greater STN and STS, but lower SOC levels than those where straw was burned. No-tillage had higher SOC levels than the stubble mulch and ploughing treatments only in the 0-50 mm soil layer. Below 100 mm soil depth, higher SOC levels were recorded in the ploughed plots. No-tillage and stubble mulch enhanced STN throughout the soil profile compared to ploughing. Ploughing and stubble mulch treatments had greater STS levels than no-tillage treatments in the upper 250 mm soil layer, and STS in the 0-450 mm soil layer was higher in mechanically weeded plots than in chemically weeded plots. Treatment combinations also showed some significant interactions on these indices, but lack of consistency made it difficult to single out the combination that was superior to others. However, to maintain or improve SOM of this Plinthosol priority should be given to no-tillage and stubble mulch management practices. Wheat grain yields over the 32 years trial period were significantly influenced by straw management and tillage methods, but not by weeding methods.
  • Authors:
    • Goulding, K. W. T.
    • Macdonald, A. J.
    • Coleman, K.
    • Chambers, B. J.
    • Bhogal, A.
    • Powlson, D. S.
    • Whitmore, A. P.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 146
  • Issue: 1
  • Year: 2012
  • Summary: Results from the UK were reviewed to quantify the impact on climate change mitigation of soil organic carbon (SOC) stocks as a result of (1) a change from conventional to less intensive tillage and (2) addition of organic materials including farm manures, digested biosolids, cereal straw, green manure and paper crumble. The average annual increase in SOC deriving from reduced tillage was 310 kg C180 kg C ha -1 yr -1. Even this accumulation of C is unlikely to be achieved in the UK and northwest Europe because farmers practice rotational tillage. N 2O emissions may increase under reduced tillage, counteracting increases in SOC. Addition of biosolids increased SOC (in kg C ha -1 yr -1 t -1 dry solids added) by on average 6020 (farm manures), 18024 (digested biosolids), 5015 (cereal straw), 6010 (green compost) and an estimated 60 (paper crumble). SOC accumulation declines in long-term experiments (>50 yr) with farm manure applications as a new equilibrium is approached. Biosolids are typically already applied to soil, so increases in SOC cannot be regarded as mitigation. Large increases in SOC were deduced for paper crumble (>6 t C ha -1 yr -1) but outweighed by N 2O emissions deriving from additional fertiliser. Compost offers genuine potential for mitigation because application replaces disposal to landfill; it also decreases N 2O emission.
  • Authors:
    • Saia, S.
    • Frenda, A. S.
    • Miceli, G. di
    • Giambalvo, D.
    • Ruisi, P.
    • Amato, G.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 5
  • Year: 2012
  • Summary: The no-tillage (NT) technique represents a valuable alternative to conventional tillage (CT) for many crops, but little research has evaluated the effects of its use on the performance of grain legumes, particularly in Mediterranean regions. The present study assessed the effects of NT compared with CT on the grain yield and N 2 fixation of chickpea ( Cicer arietinum L.), faba bean ( Vicia faba L. variety minor), pea ( Pisum sativum L.), and lentil ( Lens culinaris Medik.). The experiment was performed under rainfed conditions during four growing seasons. Nitrogen fixation was estimated using the 15N isotope dilution technique. The response of the four species to the tillage system varied significantly by year. The grain yield was significantly higher under NT than under CT only for pea and chickpea, but the differences between the two tillage techniques were consistent only when rainfall was very scarce. The percentage of N fixed differed by species in the order faba bean > chickpea > pea > lentil. The effects of tillage on the N 2 fixation process varied significantly by species and year. Nitrogen balance was positive for faba bean and lentil and negative for chickpea and pea, with no differences by tillage. The results indicate that in cereal-dominated Mediterranean agro-ecosystems NT can be a valuable option for producing grain legumes, as it can improve productivity, particularly under conditions of deficient soil moisture.
  • Authors:
    • Cavigelli, M. A.
    • Spargo, J. T.
    • Mirsky, S. B.
    • Teasdale, J. R.
    • Maul, J. E.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: There is interest in developing no-tillage systems for organic farming; however, potential limitations include the inability to control weeds and to provide sufficient crop available N. A 3-yr field experiment was conducted on organically certified land to explore roller-crimper technology for terminating a hairy vetch ( Vicia villosa Roth) cover crop in a reduced-tillage compared to a disk-tillage organic corn ( Zea mays L.) production system in Maryland. Within this tillage comparison, factors including the corn planting date and post-plant cultivation were examined for optimizing reduced-tillage organic corn production. Corn yield in roll-killed hairy vetch treatments where corn was planted by mid-June and that received high-residue cultivation was similar or higher than the best treatments with disk-killed hairy vetch. Delayed corn planting dates had little impact on corn yield in either disk- or roll-killed treatments, a result consistent with the similarity in weed biomass after cultivation, fertility, moisture, and radiation across planting dates. In 2 yr with supplemented weed populations, weed biomass was the major driver determining corn yield, which was reduced by 53 to 68% relative to weed-free control plots in the absence of post-plant cultivation, and by 21 to 28% with post-plant cultivation. In a year with low, natural weed populations, weeds had no significant influence on yield. These results demonstrate that organic corn production in a reduced-tillage roll-killed cover crop system can provide similar yields to those in a traditional tillage-based system, but also highlight the importance of maintaining low weed populations to optimize corn yield.
  • Authors:
    • Meng, F. R.
    • Benoy,G. A.
    • Chow, T. L.
    • Daigle,J. L.
    • Bourque,C. P. A.
    • Yang, Q.
  • Source: JOURNAL OF ENVIRONMENTAL QUALITY
  • Volume: 41
  • Issue: 1
  • Year: 2012
  • Summary: Runoff from crop production in agricultural watersheds can cause widespread soil loss and degradation of surface water quality. Beneficial management practices (BMPs) for soil conservation are often implemented as remedial measures because BMPs can reduce soil erosion and improve water quality. However, the efficacy of BMPs may be unknown because it can be affected by many factors, such as farming practices, land-use, soil type, topography, and climatic conditions. As such, it is difficult to estimate the impacts of BMPs on water quality through field experiments alone. In this research, the Soil and Water Assessment Tool was used to estimate achievable performance targets of water quality indicators (sediment and soluble P loadings) after implementation of combinations of selected BMPs in the Black Brook Watershed in northwestern New Brunswick, Canada. Four commonly used BMPs (flow diversion terraces [FDTs], fertilizer reductions, tillage methods, and crop rotations), were considered individually and in different combinations. At the watershed level, the best achievable sediment loading was 1.9 t ha -1 yr -1 (89% reduction compared with default scenario), with a BMP combination of crop rotation, FDT, and no-till. The best achievable soluble P loading was 0.5 kg ha -1 yr -1 (62% reduction), with a BMP combination of crop rotation and FDT and fertilizer reduction. Targets estimated through nonpoint source water quality modeling can be used to evaluate BMP implementation initiatives and provide milestones for the rehabilitation of streams and rivers in agricultural regions.