• Authors:
    • Hellin, J.
    • Wall, P.
    • Sayre, K.
    • Erenstein, O.
    • Dixon, J.
  • Source: Journal of Sustainable Agriculture
  • Volume: 36
  • Issue: 1-2
  • Year: 2012
  • Summary: Conservation agriculture's underlying principles-minimal soil disturbance, soil cover and crop rotation-are increasingly recognized as essential for sustainable agriculture. This article summarizes three contrasting cases of adapting conservation agriculture (CA) to smallholder conditions in the (sub)tropics: a) irrigated rice-wheat systems in South Asia; b) rainfed maize/wheat and irrigated wheat systems in Mexico; and c) rainfed maize in Southern Africa. In the South Asia case, farm surveys show rapid and widespread adoption of zero tillage wheat-primarily due to a substantial cost saving (15-16%). In the other cases, uptake so far has been limited-although long-term trials show continuously higher and more stable yields both for maize and wheat. Under marginal conditions CA can generate substantial yield increases-averaging some 50% over conventional smallholder maize yields of 1 ton per ha over 6 years in on-farm trails in Southern Africa. The diverse experiences attest to the wide adaptability of CA systems, which can generate clear economic and potentially enormous environmental benefits. The case studies and wider literature however also reiterate the substantial challenges in terms of targeting, adapting and adopting CA-particularly for smallholders in the (sub)tropics. CA systems are best developed in situ through a multi-stakeholder adaptive learning process to create viable CA-based options that are technically sound, economically attractive, and socially acceptable.
  • Authors:
    • Soomro, B. A.
    • Markhand, G. S.
    • Soomro, M. H.
  • Source: Pakistan Journal of Botany
  • Volume: 44
  • Issue: 1
  • Year: 2012
  • Summary: The drought is one of the biggest abiotic stresses for crop production in arid and semi-arid agriculture. Thus it is a challenge for plant scientists to screen and develop the drought tolerant cotton lines. In this study, 31 cotton genotypes/cultivars were evaluated under two irrigation regimes i.e., seven irrigations (Control) and two irrigations (Stress), using split plot design with four replications. The crop growth, yield and some physiological parameters were studied. There were high inter-varietal differences for all the parameters under control as well as drought stress. Although all the varieties for all parameters were significantly affected by drought but however, CRIS-9, MARVI, CRIS-134, CRIS-126, CRIS-337, CRIS-355 and CRIS-377 maintained highest performance for all the parameters studied under high drought conditions.
  • Authors:
    • Kabat, P.
    • Wolf, J.
    • Wit, A. J. W. de
    • Diepen, C. A. van
    • Supit, I.
    • Baruth, B.
    • Ludwig, F.
  • Source: Agricultural and Forest Meteorology
  • Volume: 164
  • Year: 2012
  • Summary: Climate change impacts on potential and rainfed crop yields on the European continent were studied using output of three General Circulation Models and the Crop Growth Monitoring System in combination with a weather generator. Climate change impacts differ per crop type and per CO 2 emission scenario. Crops planted in autumn and winter (winter wheat) may benefit from the increasing CO 2 concentration. Rainfall is sufficient and if the CO 2 concentration increase is high, yields may increase up to 2090. If the CO 2 increase is less, increasing temperatures result in declining or stagnating yields after 2050. Crops planted in spring (potato, sugar beet) initially benefit from the CO 2 increase, however as time progresses the increasing temperatures reduce these positive effects. By the end of the century yields decline in southern Europe and production may only be possible if enough irrigation water is available. In northern Europe depending on the temperature and CO 2 concentration increase, yields either stagnate or decline. However in some of the cooler regions yield increase is still possible. Crops planted in late spring and summer (maize) may suffer from droughts and high temperature in summer. By the end of the century, depending on the temperature rise, crop yields decline almost everywhere. If the temperature increase is less only in north western Europe yields remain stable.
  • Authors:
    • Tchoundjeu, Z.
    • Kalinganire, A.
    • Coe, R.
    • Sileshi, G. W.
    • Bayala, J.
    • Sinclair, F.
    • Garrity, D.
  • Source: Journal of Arid Environments
  • Volume: 78
  • Year: 2012
  • Summary: To address the decline in crop productivity in the drylands of West Africa, many initiatives have focused on combating soil degradation. Various practices including (1) parkland trees associated with crops, (2) coppicing trees, (3) green manure, (4) mulching. (5) crop rotation and intercropping, and (6) traditional soil/water conservation have been tested. The present study attempts to provide a comprehensive, quantitative synthesis of existing reports on the effect of conservation agriculture (CA) practices on crop yield response in Burkina Faso, Mali, Niger and Senegal. Out of a total of 155 reports found, 63 fulfilled all the appropriate criteria to be included in the meta-analysis of the effect of various conservation agriculture practices on the yield response of maize, millet and sorghum. The study revealed significant variability in cereal yield response (and hence risk) with all the practices examined. Despite the variability, the mean effects of the six CA practices on crop yield were more positive than negative except with parkland trees. However, for this last practice, species like Faidherbia albida exerts more positive impact on crop yield. Yield increases relative to the control were higher with green manure and mulching than with coppicing trees and parklands. Increases in yield in the six CA practices were higher on low to medium productivity sites for maize, millet and sorghum. Coppicing trees and rotations improved yields when the rainfall is >800 mm whereas the opposite happens with parkland and soil-water conservation measures. Mulching performed better when the rainfall is
  • Authors:
    • Hensley, M.
    • Bennie, A. T. P.
    • Botha, J. J.
    • Rensburg, L. D. van
  • Source: Water SA
  • Volume: 37
  • Issue: 5
  • Year: 2011
  • Summary: This review provides an overview of Water Research Commission (WRC)-funded research over the past 36 years. A total of 28 WRC reports have been consulted, 13 of these compiled by the University of the Free State, 4 by the University of Fort Hare, and the remainder mainly by the ARC-Institute for Soil Climate and Water. This work has resulted in extensive capacity building in this field - numerous technical assistants and 58 researchers have been involved, of which 23 are still active in research. The focus on the water flow processes in the soil-plant-atmosphere continuum (SPAC), with particular emphasis on processes in the soil, has greatly enhanced understanding of the system, thereby enabling the formulation of a quantitative model relating the water supply from a layered soil profile to water demand; the formulation of logical quantitative definitions for crop-ecotope specific upper and lower limits of available water; the identification of the harmful rootzone development effects of compacted layers in fine sandy soils caused by cultivation, and amelioration procedures to prevent these effects; and management strategies to combat excessive water losses by deep drainage. The explanation of the way in which SPAC is expressed in the landscape in the form of the ecotope has been beneficial with regard to the extrapolation of studies on particular SPACs to the large number of ecotopes where detailed studies have not been possible. Valuable results are reported regarding rainfall and runoff management strategies. Longer fallow periods and deficit irrigation on certain crop ecotopes improved rainfall use efficiency. On semi-arid ecotopes with high-drought-risk clay and duplex soils and high runoff losses, in-field rainwater harvesting (IRWH), designed specifically for subsistence farmers, resulted in maize and sunflower yield increases of between 30% and 50% compared to yields obtained with conventional tillage. An indication of the level of understanding of the relevant processes that has been achieved is demonstrated by their quantitative description in mathematical and empirical models: BEWAB for irrigation, SWAMP mainly for dryland cropping, and CYP-SA for IRWH. Five important related research and development needs are identified. The WRC has played, and continues to play, an important role in commissioning and funding research on water utilisation in agriculture and has clearly made an excellent contribution to the progress made in addressing the needs and requirements of subsistence, emergent and dryland farmers in South Africa.
  • Authors:
    • Kihara, J.
    • Bationo, A.
    • Mugendi, D. N.
    • Martius, C.
    • Vlek, P. L. G.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 90
  • Issue: 2
  • Year: 2011
  • Summary: Smallholder land productivity in drylands can be increased by optimizing locally available resources, through nutrient enhancement and water conservation. In this study, we investigated the effect of tillage system, organic resource and chemical nitrogen fertilizer application on maize productivity in a sandy soil in eastern Kenya over four seasons. The objectives were to (1) determine effects of different tillage-organic resource combinations on soil structure and crop yield, (2) determine optimum organic-inorganic nutrient combinations for arid and semi-arid environments in Kenya and, (3) assess partial nutrient budgets of different soil, water and nutrient management practices using nutrient inflows and outflows. This experiment, initiated in the short rainy season of 2005, was a split plot design with 7 treatments involving combinations of tillage (tied-ridges, conventional tillage and no-till) and organic resource (1 t ha -1 manure + 1 t ha -1 crop residue and; 2 t ha -1 of manure (no crop residue) in the main plots). Chemical nitrogen fertilizer at 0 and 60 kg N ha -1 was used in sub-plots. Although average yield in no-till was by 30-65% lower than in conventional and tied-ridges during the initial two seasons, it achieved 7-40% higher yields than these tillage systems by season four. Combined application of 1 t ha -1 of crop residue and 1 t ha -1 of manure increased maize yield over sole application of manure at 2 t ha -1 by between 17 and 51% depending on the tillage system, for treatments without inorganic N fertilizer. Cumulative nutrients in harvested maize in the four seasons ranged from 77 to 196 kg N ha -1, 12 to 27 kg P ha -1 and 102 to 191 kg K ha -1, representing 23 and 62% of applied N in treatments with and without mineral fertilizer N respectively, 10% of applied P and 35% of applied K. Chemical nitrogen fertilizer application increased maize yields by 17-94%; the increases were significant in the first 3 seasons ( P2 mm) and micro-aggregates fractions (53 m: P tied-ridges > conventional tillage. Also, combining crop residue and manure increased large macro-aggregates by 1.4-4.0 g 100 g -1 soil above manure only treatments. We conclude that even with modest organic resource application, and depending on the number of seasons of use, conservation tillage systems such as tied-ridges and no-till can be effective in improving crop yield, nutrient uptake and soil structure and that farmers are better off applying 1 t ha -1 each of crop residue and manure rather than sole manure.
  • Authors:
    • Kocyigit, R.
    • Rice ,C. W.
  • Source: Bulgarian Journal of Agricultural Science
  • Volume: 17
  • Issue: 4
  • Year: 2011
  • Summary: The soil surface CO 2 flux is the second largest flux in the terrestrial carbon budget after photosynthesis. Plant root and microbial respiration produce CO 2 in soils, which are important components of the global C cycle. This study determined the amount of CO 2 released during spring wheat ( Triticum aestivum L.) growth under no-till (NT) and conventional tillage (CT) systems. This experiment was conducted at Kansas State University North Agronomy Farm, Manhattan, KS, on a Kennebec silt loam. This study site was previously under dry land continuous corn production with NT and CT for more than 10 years. Spring wheat ( Triticum aestivum L.) was planted with two tillage systems (NT and CT) as four replicates in March. Surface CO 2 flux was measured weekly during plant growth. Soil water content at the surface (5 cm) tended to be greater in NT and decreased from planting to harvest. Soil microbial activity at the surface was usually higher in NT and decreased from planting to harvest, while activity was constant in the deeper depths. The higher microbial activity at the surface of NT occurred after 60 days of planting where soil water content was the most limiting factor on microbial activity. Soil CO 2 flux varied in response to changes in soil water content and the variation and magnitude of the increase was greater at higher soil water contents. Conventional tillage released 20% more CO 2 to the atmosphere compare to NT after 10 years in the North American Great Plains Regions.
  • Authors:
    • Liu, K. S.
    • Wiatrak, P.
  • Source: American Journal of Agricultural and Biological Sciences
  • Volume: 6
  • Issue: 1
  • Year: 2011
  • Summary: Problem statement: Nitrogen application timing and Nitrogen (N) rate are two important factors to influence corn production in No-Tillage (NT) system, but N recommendations may need to be revised due to insufficient rainfall in dryland rain-fed environment. Approach: This study was to determine the effects of two N application timing (planting and split application at planting and V6 corn growth stage) and five N rates (0, 45, 90, 135 and 180 kg N ha -1) on corn plant characteristics and grain yield under rain-fed and low corn yield environment. Plant characteristics included the measurement of plant height, ear height, relative chlorophyll content (SPAD) and normalized Difference Vegetation Index (NDVI). Results: Plant height and ear height at R1 stage, SPAD at R1 and NDVI at V8 and R1 increased significantly with increasing N rates, while N application timing had no effect on measured canopy characteristics. Grain yield increased from 2.2-3.8 Mg ha -1 as N rate changed from 0-180 kg ha -1. However, applying more than 90 kg N ha -1 did not significantly increase grain yields. The N application timing did not influence yield. Strong correlations were observed among corn plant characteristics and between plant NDVI at V8 and R1 stages and grain yields. Conclusion: These results indicate that N application timing was not important factor to affect corn plant characteristics and grain yield under rain-fed and low corn yield dryland conditions and we may not expect a significant grain yield increase with application exceeding 90 kg N ha -1 under these conditions. Plant NDVI at V8 and R1 stage could be a good indicator to predict corn grain yield.
  • Authors:
    • Melero, S.
    • Panettieri, M.
    • Madejon, E.
    • Gomez Macpherson, H.
    • Moreno, F.
    • Murillo, J. M.
  • Source: Soil & Tillage Research
  • Volume: 112
  • Issue: 2
  • Year: 2011
  • Summary: Long-term no-till practices (NT) have a positive effect on recovery and improving soil fertility and decreasing soil erosion. Nevertheless, long term no-till practices may also cause some inconveniences, such as soil compaction, water infiltration and problems in seed germination. Thus, in the present work we assess the effects of the implementation (October 2008) of a traditional tillage (mouldboard ploughing) (TT) and reduced tillage (chiselling) (RT) on soil quality in a dryland calcareous soil (Leptic Typic Xerorthent) after 8 years of soil no-till management (NT) in SW Spain. The results were compared to those found under no-till. We hypothesised that C fractions and biological properties would be adequate indicators of soil quality changes. To test the hypothesis soil samples were collected at three depths (0-5, 5-10 and 10-25 cm) and in three sampling periods, after tillage and sowing (January 2009) after harvesting (June 2009) a vetch crop ( Vicia sativa, L) and after tillage and sowing (January 2010) of a wheat crop ( Triticum aestivum, L). Total organic carbon (TOC) and carbon labile fractions (active carbon (AC) and water soluble carbon (WSC)) were determined. Biological status was evaluated by the analysis of soil microbial biomass carbon and nitrogen (MBC and MBN) and enzymatic activities [dehydrogenase activity (DHA), and beta-glucosidase activity (Glu)]. The implementation of chiselling did not cause depletion in most of the studied soil properties compared to no-till in the first 5 cm of soil. However, the application of traditional tillage reduced 23% of TOC, 27% of WSC, 12% of AC, 19% of MBC, 44% of MBN, 37% of DHA and 51% of Glu in the upper layer of the soil (0-5 cm depth) with respect to no-till. Soil organic carbon and microbial parameter values decreased as depth increased, particularly in conservation tillage systems (RT and NT) in all sampling periods. Under our conditions, dryland Mediterranean areas, the mouldboard ploughing is not considered a suitable soil tillage system since it showed an early negative effect on soil organic fractions and biochemical quality. Although further studies would be necessary, the use of chiselling could be a solution in case of problems related to no-till.
  • Authors:
    • Nielsen, D. C.
  • Source: Field Crops Research
  • Volume: 124
  • Issue: 3
  • Year: 2011
  • Summary: Forages could be used to diversify reduced and no-till dryland cropping systems from the traditional wheat ( Triticum aestivum L.)-fallow system in the semiarid central Great Plains. Forages present an attractive alternative to grain and seed crops because of greater water use efficiency and less susceptibility to potentially devastating yield reductions due to severe water stress during critical growth stages. However, farmers need a simple tool to evaluate forage productivity under widely varying precipitation conditions. The objectives of this study were to (1) quantify the relationship between crop water use and dry matter (DM) yield for soybean ( Glycine max L. Merrill), (2) evaluate changes in forage quality that occur as harvest date is delayed, and (3) determine the range and distribution of expected DM yields in the central Great Plains based on historical precipitation records. Forage soybean was grown under a line-source gradient irrigation system to impose a range of water availability conditions at Akron, CO. Dry matter production was linearly correlated with water use resulting in a production function slope of 21.2 kg ha -1 mm -1. The slope was much lower than previously reported for forage production functions for triticale ( X Triticosecale Wittmack) and millet ( Setaria italic L. Beauv.), and only slightly lower than slopes previously reported for corn ( Zea mays L.) and pea ( Pisum sativa L.) forage. Forage quality was relatively stable during the last four weeks of growth, with small declines in crude protein (CP) concentration. Values of CP concentration and relative feed value indicated that forage soybean was of sufficient quality to be used for dairy feed. A standard seed variety of maturity group VII was found to be similar (in both productivity and quality) to a variety designated as a forage type. The probability of obtaining a break-even yield of at least 4256 kg ha -1 was 90% as determined from long-term precipitation records used with the production function. The average estimated DM yield was 5890 kg ha -1 and ranged from 2437 to 9432 kg ha -1. Regional estimates of mean forage soybean DM yield ranged from 4770 kg ha -1 at Fort Morgan, CO to 6911 kg ha -1 at Colby, KS. Forage soybean should be considered a viable alternative crop for dryland cropping systems in the central Great Plains.