• Authors:
    • Navarrete, L.
    • Kozak, M.
    • Hernandez Plaza, E.
    • Gonzalez-Andujar, J. L.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 140
  • Issue: 1-2
  • Year: 2011
  • Summary: This study investigated whether the choice of a tillage system (no-tillage, minimum tillage or traditional tillage) affected weed diversity in a 23 years cereal-leguminous rotation system in Spain. Weed diversity was assessed using common diversity indices: species richness, Shannon's index and Pielouis evenness. Linear mixed-effects models were employed to compare the tillage systems. It was found that after 23 years no large differences between tillage systems have arisen related to weed diversity. Only minimum tillage appeared to support, on average, more species than the two other tillage systems. Richness, Shannon diversity index and evenness varied largely through the years in all tillage systems but this variation was not related to type of crop sown (cereal or leguminous). Our results highlight that conservation tillage practices did not represent any concern for weed diversity conservation in cereal-leguminous rotations in the conditions of central Spain.
  • Authors:
    • Stevenson, F. C.
    • Legere, A.
    • Benoit, D. L.
  • Source: Weed Science
  • Volume: 59
  • Issue: 1
  • Year: 2011
  • Summary: A conservation tillage study provided the opportunity to test whether tillage effects on the germinable weed seedbank would be consistent across different crop rotations and to investigate the potential residual effects of herbicide treatments terminated 12 yr earlier. Our objective was to measure the effects of tillage (moldboard plow [MP] vs. chisel plow [CP] vs. no-till [NT]), crop rotation (2-yr barley-red clover followed by 4-yr barley-canola-wheat-soybean rotation, compared to a cereal monoculture), and of a prior weed management factor (three intensity levels of herbicide use) on the density, diversity, and community structure of weed seedbanks. Species richness, evenness (Shannon's E), and diversity (Shannon's H′) of spring seedbanks varied little across treatments and over time. Total seedbank density generally increased as tillage was reduced, with some variations due to weed management in 1993 and crop rotation in 2006. Crop rotations generally had smaller seedbanks with fewer species than the monoculture. In 1993, seedbanks with minimum weed management were twice as dense as those with intensive or moderate weed management (approximately 6,000 vs. 3,000 seed m -2). By 2006, seed density averaged 6,838 seed m -2 across intensive and moderate weed management regardless of tillage, but was nearly twice as large in NT (12,188 seed m -2) compared to MP (4,770 seed m -2) and CP (7,117 seed m -2) with minimum weed management (LSD 0.005=4488). Species with abundant seedbanks responded differently to treatments. Barnyardgrass and green foxtail had larger seedbanks in the monoculture than in the rotation. Common lambsquarters and pigweed species had large seedbanks in tilled treatments in the rotation, whereas yellow foxtail and field pennycress contributed to the large seedbanks observed in NT treatments. The latter two species were also associated with residual effects of weed management treatments (terminated 12 yr earlier) in NT. The differential seedbank response of weed species, attributed in part to contrasting weed emergence patterns and agronomic practice effects on seed rain, explained some of the weak treatment effects observed for total seedbank density and diversity. The large weed seedbanks observed in NT plots after 18 yr confirms the importance of seed rain and seedbank management for the sustainability of NT systems.
  • Authors:
    • Officer, S. J.
    • Kelly, K.
    • Kearney, G. A.
    • Graham, J. F.
  • Source: Annual Meeting of the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
  • Year: 2011
  • Authors:
    • Kiese, R.
    • Butterbach-Bahl, K.
    • Reeves, S. H.
    • Dalal, R. C.
    • Wang, W.
  • Source: Global Change Biology
  • Volume: 17
  • Issue: 10
  • Year: 2011
  • Authors:
    • Alvarez, C. R.
    • Costantini, A. O.
    • Bono, A.
    • Taboada, M. A.
    • Boem, F. H. G.
    • Fernandez, P. L.
    • Prystupa, P.
  • Source: Revista Brasileira de Ciência do Solo
  • Volume: 35
  • Issue: 6
  • Year: 2011
  • Summary: One of the expected benefits of no-tillage systems is a higher rate of soil C sequestration. However, higher C retention in soil is not always apparent when notillage is applied, due e.g., to substantial differences in soil type and initial C content. The main purpose of this study was to evaluate the potential of no-tillage management to increase the stock of total organic C in soils of the Pampas region in Argentina. Forty crop fields under no-tillage and conventional tillage systems and seven undisturbed soils were sampled. Total organic C, total N, their fractions and stratification ratios and the C storage capacity of the soils under different managements were assessed in samples to a depth of 30 cm, in three layers (0–5, 5– 15 and 15–30 cm). The differences between the C pools of the undisturbed and cultivated soils were significant (p < 0.05) and most pronounced in the top (0– 5 cm) soil layer, with more active C near the soil surface (undisturbed > no-tillage > conventional tillage). Based on the stratification ratio of the labile C pool(0–5/5– 15 cm), the untilled were separated from conventionally tilled areas. Much of the variation in potentially mineralizable C was explained by this active C fraction (R2 = 0.61) and by total organic C (R2 = 0.67). No-till soils did not accumulate more organic C than conventionally tilled soils in the 0–30 cm layer, but there was substantial stratification of total and active C pools at no till sites. If the C stratification ratio is really an indicator of soil quality, then the C storage potential of no-tillage would be greater than in conventional tillage, at least in the surface layers. Particulate organic C and potentially mineralizable C may be useful to evaluate variations in topsoil organic matter.
  • Authors:
    • Abreu, S. L.
    • Godsey, C. B.
    • Edwards, J. T.
    • Warren, J. G.
  • Source: Soil & Tillage Research
  • Volume: 117
  • Year: 2011
  • Summary: Intensive tillage during the last century has greatly reduced organic carbon contents of Oklahoma cropland. Increased public interest in carbon sequestration and the potential for carbon storage in no-till soils to offset CO2 emissions has brought about the need for accurate estimates of carbon sequestration in Oklahoma. Eight locations across Oklahoma were soil sampled to determine the impact of no-till farming practices on soil carbon storage. Locations consisted of side by side no-till and tilled fields sampled at four sites in each field. Samples were divided into 0–10, 10–20, 20–40, 40–70, and 70–110 cm depths and analyzed for organic carbon (OC) and total nitrogen (TN). Averaged across locations and depth, the concentration of organic carbon (OC) was 0.7 g kg−1 greater in no-till compared to tilled fields. As expected, differences between no-till and conventional till were dependent on length of time in no-till and annual precipitation. The greater the time in no-till management and the higher the annual precipitation, the greater the carbon stocks compared to conventional till fields. Despite the high degree of variation among sample locations, the mass of OC was significantly (p = 0.07), greater in the NT compared to that found in the CT fields, with the average difference being 8.6 Mg ha−1. The highest OC accumulation was observed in Miami with an average of 3.5 Mg ha−1 year−1, while at Lahoma 2 and Goodwell no accumulation of OC was observed. Eliminating tillage operations can increase OC accumulation with the presence of adequate rainfall and an extended period of time.
  • Authors:
    • Cockfield, G.
    • Maraseni, T. N.
  • Source: Agricultural Systems
  • Volume: 104
  • Issue: 6
  • Year: 2011
  • Authors:
    • Booker, J.
    • Lascano, R.
    • Acosta-Martinez, V.
    • Calderon, F.
    • Zobeck, T.
    • Upchurch, D.
  • Source: Biology and Fertility of Soils
  • Volume: 47
  • Issue: 6
  • Year: 2011
  • Summary: In dryland agriculture in semiarid regions, crop establishment is not always possible because precipitation may not be sufficient. Modification of soil properties can improve the soil quality and functioning including soil water capture and storage capacity for crop production in dryland conditions. ARS scientists established a study near Lubbock, Texas in 2003 to compare the soil properties under different dryland cropping systems and tillage management. After only 3 years, this study detected increases in soil microbial community size and enzyme activities important for nutrient cycling under rotations with a winter cover crop such as cotton-rye-sorghum and haygrazer-rye compared to continuous cotton or sorghum-cotton at 0-10 cm soil depth. After 5 years, higher soil total C was found under Hay-Rye compared to the other systems. In addition, microbial properties were already impacted in all alternative systems (haygrazer-rye, cotton-rye-sorghum and cotton-sorghum) studied compared to continuous cotton. Several microbial properties indicative of increased soil water availability were also higher under the alternative rotations to continuous cotton. However, continuation of this study is vitally important for the long-term evaluation and confirmation of these trends, and their implications in water management, soil quality and crop productivity in dryland.
  • Authors:
    • Abdellaoui, Z.
    • Teskrat, H.
    • Belhadj, A.
    • Zaghouane, O.
  • Source: Options Mediterranennes
  • Issue: 96
  • Year: 2011
  • Summary: The comparative study of reduced tillage, zero tillage and conventional tillage conducted during 5 years in the sub-humid zone of Algeria showed a difference of the development of durum wheat and changes of some soil characteristics. In the first year experiment, the yield was higher in the conventional tillage compared with reduced tillage and no-tillage. After the 3rd year, better yields were obtained with no-till with a 10 q/ha rise compared with conventional tillage. This confirms that the production of wheat under no till is improved year by year. However, after the 5th year of experiment, the high soil moisture at the seeding has generated lower yields. The different tillage practices have generated differences in soil characteristics. In fact a better water retention and a better content in organic matter in the three studied layers, were observed with no till. The bulk density shows a clear variation at the surface layer (0-8 cm) with the highest density in the conventional tillage.
  • Authors:
    • Raman, A.
    • Ladha, J. K.
    • Kumar, V.
    • Sharma, S.
    • Piepho, H. P.
  • Source: Field Crops Research
  • Volume: 121
  • Issue: 3
  • Year: 2011
  • Summary: Normally, the data generated from farmer participatory trials (FPT) are highly unbalanced due to variation in the number of replicates of different treatments, the use of different varieties, farmers’ management of the trials, and their preferences for testing different treatments. The incomplete nature of the data makes mixed models the preferred class of models for the analysis. When assessing the relative performances of technologies, stability over a range of environments is an important attribute to consider. Most of the common models for stability may be fitted in a mixed-model framework where environments are a random factor and treatments are fixed. Data from on-farm trials conducted in the Indo-Gangetic Plain (IGP) of South Asia under the umbrella of Rice–Wheat Consortium (RWC) were analyzed for grain yield stability using different stability models. The objective was to compare improved resource management technologies with farmers’ practice. The variance components of an appropriate mixed model serve as measures of stability. Stability models were compared allowing for (i) heterogeneity of error variances and (ii) heterogeneity of variances between environments for farmers-within-environment effects. Mean comparisons of the treatments were made on the basis of the best fitting stability model. Reduced-till (non-puddled) transplanted rice (RT-TPR) and reduced-till drill-seeded wheat using a power tiller – operated seeder with integrated crop and resource management RTDSW(PTOS)ICRM ranked first in terms of both adjusted mean yield and stability.