• Authors:
    • Li, J.
    • Xu, Y.
    • Yang, J.
    • Liu, J.
    • Wang, J.
    • Zhou, S.
  • Source: Hydrological Processes
  • Volume: 26
  • Issue: 8
  • Year: 2012
  • Summary: Eddy covariance flux measurements were performed at a cotton crop site of an oasis in northern Xinjiang, northwest China from 2008 to 2010 in order to study ecosystem evapotranspiration (ET). The soil surface area was approximately 80% covered by plastic film mulch and a cotton crop was grown with a mean population density of around 24 plants m-2 under drip irrigation. The total annual ET was measured to be 560 mm, which was 350 mm more than the average annual mean precipitation for the time period 19632006. Due to the low vapor pressure deficit associated with low temperatures, the ET was low from November to March. The ET totaled 538 mm during the cotton crop growing season, generally from early-April through mid-October. Mean daily ecosystem ET was 1.41.6 mm day-1 in April and May, 3.44.7 mm day-1 from June through August, 1.82.3 mm day-1 in September and 0.70.8 mm day-1 in October. The diurnal variations of ET in all months were consistent with those of net radiation, although the leaf area index (LAI) and climate conditions changed substantially. Soil water content was not a limiting factor for ET during the period from April through September, as the crop was regularly irrigated. Therefore, ET was mainly controlled by the available energy in April and May, and by leaf area from June through September. Due to a complete lack of irrigation, ET was constrained by soil water in October. These results of ET variability are helpful for improved allocation of water resources and agricultural water use practices in the region. Copyright (c) 2011 John Wiley & Sons, Ltd.
  • 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:
    • Higginbotham, R. W.
    • Jones, S. S.
    • Carter, A. H.
  • Source: Sustainability
  • Volume: 3
  • Issue: 8
  • Year: 2011
  • Summary: In Washington, over fifty percent of the wheat produced under rainfed conditions receives less than 300 mm of annual precipitation. Hence, a winter wheat-summer fallow cropping system has been adopted to obtain adequate moisture for winter wheat production. Current tilled fallow systems are exposed to significant soil degradation from wind and water erosion. As a result, late-planted no-till fallow systems are being evaluated to mitigate erosion concerns. The objective of this study was to evaluate current cultivars under late-planted no-till fallow systems to identify whether current breeding schemes in tilled fallow systems could select productive cultivars in late-planted no-till fallow systems. Thirty cultivars were planted in a split-plot design with fallow type as the main plot and genotype as the sub-plot. Fallow types evaluated were a tilled fallow system and a late planted no-till fallow system. Data were collected on heading date, plant height, grain volume weight, grain yield, and grain protein content. Analysis of variance was conducted on data across locations. Results were significant for all traits except for grain protein content. The late-planted no-till fallow system headed 16 days later was 5 cm shorter, yielded 36% less, and had a grain volume weight 3% less than the tilled fallow system. The lower yield and grain volume weight potential is hypothesized to be due to the 16 day delay in heading date leading to warmer temperatures during grain fill and a shorter duration. In order to breed wheat to be highly productive under a late-planted no-till fallow system, directly selecting in this system for early spring growth and earlier heading dates will be essential.
  • Authors:
    • Mehrabi,P.
    • Daliri,M. S.
    • Homayoun,H.
  • Source: Middle-East Journal of Scientific Research
  • Volume: 9
  • Issue: 3
  • Year: 2011
  • Summary: To measure the relationship between chlorophyll stress resistances in experimental maize cultivars Using 5 Maize genotypes in four replications and with two irrigation and dry farming conditions in a randomized complete block design in the 2010-2011 agricultural years in Ardabil region was carried out. To calculate the amount of stress tolerance of genotypes has been used of Fernandez stress tolerance indexes. And the chlorophyll content of leaves with the CCI-200 device was measured. The results showed that stress-resistant genotypes with higher potential yield and chlorophyll content were more than half resistant cultivars. According to the results of genotypes BC678 and BC404 have a highest chlorophyll index and the amount of yield and the most resistant genotypes to the drought.
  • Authors:
    • Kondratieff, B. C.
    • Booher, M. R.
    • Goldhamer, D. A.
    • Hurisso, T. T.
    • Davis, J. G.
    • Brummer, J. E.
    • Stromberger, M. E.
    • Stonaker, F. H.
  • Source: Applied Soil Ecology
  • Volume: 48
  • Issue: 2
  • Year: 2011
  • Summary: We evaluated the effects of soil amendments on earthworm communities in organic annual forage and perennial pasture systems in northern Colorado. In the annual forage study (1) an annual warm season grass teff ( Eragrostis tef) and (2) bare fallow were main plot treatments and received one of three soil amendments: (1) composted dairy manure (CDM), (2) raw dairy manure (RDM), and (3) no amendment as control. For the perennial pasture study, CDM was topdressed onto a grass mixture consisting of orchardgrass, smooth and meadow bromegrass at rates ranging from 0 to 44.8 Mg ha -1. At both sites, earthworm and soil samples were collected in July 2009. The earthworms identified from both systems were composed of endogeic species Aporrectodea rosea (Savigny), A. tuberculata (Eisen), and A. turgida (Eisen), the first being found only in the perennial pasture. In the annual forage study, earthworm total abundance did not differ between teff and bare fallow treatments. However, within bare fallow treatment, earthworm total abundance was significantly affected by soil amendment, with CDM averaging approximately 1.4 and 5.4 times greater earthworm total abundance than RDM and the control, respectively. Earthworm total abundance was found to be positively correlated with soil Cu ( R=0.51, P=0.03) and K ( R=0.58, P=0.01). In the perennial pasture, earthworm total abundance tended to increase with an increase in the CDM rate to 33.6 Mg ha -1. However, no further increase was observed when the CDM rate was increased to 44.8 Mg ha -1. At this site, earthworm total abundance was negatively correlated with EC ( R=-0.37, P=0.02). Our results suggest that high quality (low C/N ratio) dairy manure is important for maintaining a high earthworm population. Larger CDM application rates appear to discourage earthworm populations probably due to salinity stress. Further study is necessary to elucidate the exact effects of manure quality and quantity on earthworm populations in annual forages and perennial pastures.
  • 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:
    • Machado, S.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 1
  • Year: 2011
  • Summary: Use of crop residues for biofuel production raises concerns on how removal will impact soil organic carbon (SOC). Information on the effects on SOC is limited and requires long-term experimentation. Fortunately, Pendleton long-term experiments (LTEs), dating to the 1930s, provide some answers. This study compared crop residue inputs and SOC balance in conventional tillage (CT) winter wheat ( Triticum aestivum L.)-summer fallow (WW-SF) systems with annual rotation of WW and spring pea ( Pisum sativum L.). The WW-SF consisted of crop residue (CR-LTE) (0-90 N ha -1 yr -1, 11.2 Mg ha -1 yr -1 of steer ( Bos taurus) manure and 1.1 Mg ha -1 yr -1) of pea vines additions, residue burning, and tillage fertility (TF-LTE) (tillage-plow, disc, sweep, and N (0-180 kg ha -1)). Winter wheat-pea (WP-LTE) rotation treatments included maxi-till (MT-disc/chisel), fall plow (FP), spring plow (SP), and no-till (NT). Soils were sampled (0-60-cm depth) at 10-yr intervals, and grain yield and residue data collected every year. In WW-SF systems, SOC was maintained only by manure addition and depleted at a rate of 0.22 to 0.42 Mg ha -1 yr -1 in other treatments. In WP-LTE, MT, FP, SP, and NT treatments increased SOC at the rate of 0.10, 0.11, 0.02, and 0.89 Mg ha -1 yr -1, respectively. Minimum straw biomass to maintain soil organic carbon (MSB) in the CR-LTE, TF-LTE, and WP-LTE was 7.8, 5.8, and 5.2 Mg ha -1 yr -1, respectively. Winter wheat-SF straw production was lower than MSB, therefore residue removal exacerbated SOC decline. Harvesting straw residues under NT continuous cropping systems is possible when MSB and conservation requirements are exceeded.
  • Authors:
    • Miyamoto, S.
    • Nesbitt, M.
  • Source: HortTechnology
  • Volume: 21
  • Issue: 5
  • Year: 2011
  • Summary: Soil salinity management is a factor for successful production of pecan ( Carya illinoinensis) in arid southwestern United States. An exploratory study was performed to evaluate the effect of various soil management practices on salt leaching in basin-irrigated orchards developed on alluvial soils (Torrifluvents, Entisols) of the middle Rio Grande Basin. The practices evaluated were ripping, minimum-till chiseling, and soil profile modification. For ripping, parabolic shanks were passed through the center section (4 to 8 ft wide) between each tree row to a depth ranging from 18 to 36 inches. Minimum-till chisels included 7- and 30-inch shanks, equipped with coulters to reduce break up of the ground surface. Soil profile modification consisted of trenching with a backhoe and profile mixing with a large excavator. The effectiveness of these methods was evaluated by measuring soil salinity and moisture in treated and untreated zones at 17 test sites. Both ripping and minimum-till deep chiseling helped improve salt leaching, and the effectiveness of salt leaching increased as working depths approach the thickness of the clayey layer. However, annual ripping of the center section of each tree row space may not provide wide enough zones to alleviate salt stress to the trees. Straight shanks prune but do not lift tree roots, thus appearing to be better suited for chiseling closer to tree rows. Soil profile modification was highly effective in leaching salts. From the view of minimizing soil aggregate destruction and of maintaining a leveled floor, minimum-till deep chiseling, followed by the use of sand-topdressing and minimum-till shallow chisels for maintenance may prove to be more desirable than conventional ripping, especially in soil types consisting of silty clay loam.
  • Authors:
    • Mupangwa, W.
    • Jewitt, G. P. W.
  • Source: Physics and Chemistry of the Earth, Parts A/B/C
  • Volume: 36
  • Issue: 14-15
  • Year: 2011
  • Summary: Crop output from the smallholder farming sector in sub-Saharan Africa is trailing population growth leading to widespread household food insecurity. It is therefore imperative that crop production in semi-arid areas be improved in order to meet the food demand of the ever increasing human population. No-till farming practices have the potential to increase crop productivity in smallholder production systems of sub-Saharan Africa, but rarely do because of the constraints experienced by these farmers. One of the most significant of these is the consumption of mulch by livestock. In the absence of long term on-farm assessment of the no-till system under smallholder conditions, simulation modelling is a tool that provides an insight into the potential benefits and can highlight shortcomings of the system under existing soil, climatic and socio-economic conditions. Thus, this study was designed to better understand the long term impact of no-till system without mulch cover on field water fluxes and maize productivity under a highly variable rainfall pattern typical of semi-arid South Africa. The simulated on-farm experiment consisted of two tillage treatments namely oxen-drawn conventional ploughing (CT) and ripping (NT). The APSIM model was applied for a 95 year period after first being calibrated and validated using measured runoff and maize yield data. The predicted results showed significantly higher surface runoff from the conventional system compared to the no-till system. Predicted deep drainage losses were higher from the NT system compared to the CT system regardless of the rainfall pattern. However, the APSIM model predicted 62% of the annual rainfall being lost through soil evaporation from both tillage systems. The predicted yields from the two systems were within 50 kg ha(-1) difference in 74% of the years used in the simulation. In only 9% of the years, the model predicted higher grain yield in the NT system compared to the CT system. It is suggested that NT systems may have great potential for reducing surface runoff from smallholder fields and that the NT systems may have potential to recharge groundwater resources through increased deep drainage. However, it was also noted that the APSIM model has major shortcomings in simulating the water balance at this level of detail and that the findings need to be confirmed by further field based and modelling studies. Nevertheless, it is clear that without mulch or a cover crop, the continued high soil evaporation and correspondingly low crop yields suggest that there is little benefit to farmers adopting NT systems in semiarid environments, despite potential water resources benefits downstream. In such cases, the potential for payment for ecosystem services should be explored.
  • 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.