• Authors:
    • Walling, D. E.
    • Russell, M. A.
    • Taylor, P.
    • Ficken, K. J.
    • Blake, W. H.
  • Source: Geomorphology
  • Volume: 139
  • Year: 2012
  • Summary: A Compound Specific Stable Isotope (CSSI) sediment tracing approach is evaluated for the first time in an agricultural catchment setting against established geochemical fingerprinting techniques. The work demonstrates that novel CSSI techniques have the potential to provide important support for soil resource management policies and inform sediment risk assessment for the protection of aquatic habitats and water resources. Analysis of soil material from a range of crop covers in a mixed land-use agricultural catchment shows that the carbon CSSI signatures of particle-reactive fatty acids label surface agricultural soil with distinct crop-specific signatures, thus permitting sediment eroded from each land-cover to be tracked downstream. High resolution sediment sampling during a storm event and analysis for CSSI and conventional geochemical fingerprints elucidated temporal patterns of sediment mobilisation under different crop regimes and the specific contribution that each crop type makes to downstream sediment load. Pasture sources (65% of the catchment area) dominated the sediment load but areal yield (0.13 +/- 0.02 t ha(-1)) was considerably less than that for winter wheat (0.44 +/- 0.15 t ha(-1)). While temporal patterns in crop response matched runoff and erosion response predictions based on plot-scale rainfall simulation experiments, comparison of biomarker and geochemical fingerprinting data indicated that the latter overestimated cultivated land inputs to catchment sediment yield due to inability to discriminate temporary pasture (in rotation) from cultivated land. This discrepancy, however, presents an opportunity since combination of the two datasets revealed the extremely localised nature of erosion from permanent pasture fields in this system (estimated at up to 0.5 t ha(-1)). The novel use of CSSI and geochemical tracers in tandem provided unique insights into sediment source dynamics that could not have been derived from each method alone. Research into CSSI signature development (plant and soil processes) and the influence of cultivation regimes are required to support future development of this new tool. (C) 2011 Elsevier B.V. All rights reserved.
  • 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:
    • Beasley, J. P.,Jr.
    • Tubbs, R. S.
    • Lee, R. D.
    • Grey, T. L.
    • Jackson, J. L.
  • Source: Peanut Science
  • Volume: 38
  • Issue: 1
  • Year: 2011
  • Summary: Most peanut ( Arahcis hypogaea L.) production occurs under highly intensive conventional tillage systems. With recent volatility in input prices, reducing tillage trips is a viable way of reducing production costs. However, growers can experience yield loss when switching from conventional tillage to strip-tillage in peanut on certain soil types due to the lack of an elevated bed at harvest time. Studies were conducted to compare standard strip-till with strip-till on two-row raised beds as well as rip and beds prepared in the fall. Comparisons were made on a coarse textured soil at Tifton, GA and a fine textured soil at Plains, GA. The three bed types, with and without wheat cover, were evaluated over two years at both locations. No effects of cover or interactions with bed type were present. At Plains, the rip and bed and raised bed reduced digging losses by 62 and 47%, respectively. Soil compaction within the harvest depth was reduced by 3.3 and 4.7 times by the raised bed and rip and bed, respectively compared to flat strip-till. The rip and bed increased peanut yield by 465 kg ha -1 over flat bed. At Tifton, no significant differences in yield or digging losses occurred between tillage methods. Soil compaction in the harvest depth was reduced by 1.9 and 2.5 times by raised bed and rip and bed, respectively on this coarse soil type. Reduced compaction and digging losses along with increased yield suggest bedding is more important on finer textured soils.
  • Authors:
    • Arnold, J. G.
    • Jin, V. L.
    • Johnson, M. V. V.
    • Haney, R. L.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 141
  • Issue: 3-4
  • Year: 2011
  • Summary: The effects of biosolids application rate and history on soil potential C and N mineralization were measured over a 112-day laboratory incubation. Soils were collected from a large-scale biosolids recycling operation that surface-applies anaerobically digested Class B biosolids for commercial forage production. Five treatments were evaluated: unamended control; 22 Mg dry biosolids ha -1 y -1 applied for 25 years; 22, 45, and 67 Mg ha -1 y -1 applied for 8 years. Biosolids additions enhanced total soil organic C by 32-92% and total N by 30-157% compared to unamended soils. Total N increased with application rate and was dominated by nitrate-N. Potential C mineralization (cumulative CO 2 produced) was 11-62% greater in amended soils compared to controls and highest at 67 Mg ha -1 y -1. Net N mineralization and immobilization were highest early in the incubation for 45 and 67 Mg ha -1 y -1 treatments. No significant differences in potential C and N mineralization between controls and soils amended at the lowest rate for 8 or 25 years suggests that biosolids applications at 22 Mg ha -1 y -1 are sustainable over the long-term. Higher potential N mineralization rates and soil nitrate concentrations under higher application rates may increase the risk of off-site nutrient transport and requires further evaluation.
  • Authors:
    • Sanadze, E.
    • Weismiller, R.
    • Kirvalidze, D.
    • Kvrivishvil, T.
    • Korakhashvili, A.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 42
  • Issue: 7
  • Year: 2011
  • Summary: In 2006, the International Organization of Christian Charities (IOCC) began a program in the country of Georgia to establish an improved dairy enterprise in the villages of Minadze and Ghreli in the Akhaltsikhe district. To correctly determine the fertility requirements for the use of either mineral or organic fertilizer materials for improving soil fertility for legume grain crops (beans, peas, soybeans, etc.) and perennial pastures (a mixture of perennial cereal grasses and perennial legumes) and for the proper management of these soils, it was necessary to understand the geomorphic, chemical, and physical characteristics of the soils of this region. Soils of this region belong to a sub-type of Cinnamonic Calcareous soils. The characteristics of these soils as well as their fertility and soil management needs were ascertained. Appropriate amounts of mineral and organic fertilizers needed for the proper growth of legume crops and perennial pastures as well as timing of application are presented.
  • Authors:
    • Kussman, R. D.
    • Kremer, R. J.
  • Source: Agroforestry Systems
  • Volume: 83
  • Issue: 2
  • Year: 2011
  • Summary: Intercropping alleys in agroforestry provides an income source until the tree crop produces harvestable yields. However, cultivation of annual crops decreases soil organic matter and increases soil erosion potential, especially on sloping landscapes. Perennial crops maintain a continuous soil cover, increase water infiltration, reduce soil erosion, and improve overall soil quality. The objective of this on-farm study was to assess the effects of a perennial legume, kura clover ( Trifolium ambiguum M. Bieb.), on soil quality in a recently established pecan ( Carya illinoinensis Wangenh. C. Koch) orchard. The pecan-kura clover agroforestry practice was established on deep loess soils of the Missouri River hills landscape. These silt loams are on 2-20% slopes and can be highly erosive. Kura clover, introduced as the alley crop 5 years after pecan planting, was selected based on its perennial growth habit, nitrogen-fixing ability, winter hardiness, high forage quality, and soil conservation properties. Kura clover was seeded in 2001 and harvested for hay annually beginning 2003. Soil quality indicators of total organic C, total N, water-stable aggregates, and selected soil enzymes were determined on surface soil samples collected annually after kura clover establishment. Soil organic C and activities of soil enzymes increased compared with cultivated and grass pasture control soils by the eighth year of establishment. Water-stable aggregation improved by 50% and surface soil shear strength improved significantly ( P<0.05) in alleys compared with control sites. Results illustrate that kura clover as the alley-cropped component improved soil fertility and biological activity through increased organic matter and improved soil structure, and yielded high quality forage valuable for the cattle-feeding operation. Kura clover maintained or improved soil quality, reduced soil erosion potential, and benefited pecan growth by providing a source of soil nitrogen and improving soil structure for adequate water infiltration and aeration.
  • Authors:
    • Lavee, S.
  • Source: Acta Horticulturae 888: International Symposium on Olive Irrigation and Oil Quality
  • Issue: 888
  • Year: 2011
  • Summary: The olive commodity spread in ancient times hand in hand with western civilization in the Mediterranean basin. It was till recently and in many regions still is a highly traditionally cultivated commodity. Table olives were subjected about 200 years ago to irrigation and intensification. This was unacceptable in olive cultivation for oil extraction. During the last century the economy of the olive industry declined and became questionable. A drastic increase in efficiency of the olive oil industry was obligatory for its survival. In the nineteen fifties, an approach to intensify the olive oil industry was initiated using irrigation and modern nutrition. The initial results indicated a significant increase in production without reducing oil quality. Slight changes in taste occurred occasionally due to quantitative changes of some oil constituents but oil quality was not affected. Some of these oils gained high prizes in international competitions. Some cultivars responded to irrigation better than others regarding growth, fruit yield and relative oil content. Thus, selection and breeding of responsive cultivars to intensification was initiated. Once responsive cultivars were identified and planted commercially in pioneering orchards, a revolution of the olive oil industry was initiated. An increase in both fruit and oil yield up to more than five times that in traditional orchards was achieved. This increased production and tree uniformity initiated the development of new orchard systems, advanced mechanization and oil mill technologies reducing manual labor. This attracted large scale orchard development in traditional, new and marginal regions. Basis on this development it can be concluded that the introduction of irrigation revolutionized the world's olive oil industry from a traditional barely economic one to a thriving modern economical developing industry.
  • 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:
    • Mchunu, C. N.
    • Lorentz, S.
    • Jewitt, G.
    • Manson, A.
    • Chaplot, V.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 4
  • Year: 2011
  • Summary: Although no-till (NT) is now practiced in many countries of the world, for most smallholders, the crop residues are of such a value that they cannot be left on the soil surfaces to promote soil protection, thus potentially limiting NT benefits and adoption. In this study our main objective was to evaluate runoff, soil, and soil organic carbon (SOC) losses from traditional small-scale maize ( Zea mays) field under conventional tillage (T) and NT, with crop residues cover of less than 10% during the rainy season, in South Africa. Six runoff plots of 22.5 m 2 (2.25*10 m) under NT and T since 2002 were considered. At each plot, soil bulk density (rho b) and SOC content of the 0-0.02 m layer were estimated at nine pits. Top-soil SOC stocks were 26% higher under NT than under T ( P=0.001). The NT reduced soil losses by 68% (96.8 vs. 301.5 g m -2 yr -1, P=0.001) and SOC losses by 52% (7.7 vs. 16.2 g C m -2 yr -1, P=0.001), and differences in runoff were not significant. Dissolved organic carbon accounted for about 10% of total SOC losses and showed significantly higher concentrations under T than NT (1.49 versus 0.86 mg C m -2 yr -1). The less erosion in NT compared to T was explained by a greater occurrence under NT of indurated crusts, less prone to soil losses. These results showed the potential of NT even with low crop residue cover (<10%) to significantly reduce soil and SOC losses by water under small-scale agriculture.