Waterlogging and salinity are reducing the productivity of irrigated agriculture on clay soils in south east Australia. We compared five drainage treatments: (1) undrained control (Control); (2) mole drains (Mole); (3) mole drains formed beneath gypsum-enriched slots (GES) (Mole + GES); (4) shallow pipe drains installed beneath GES (Shallow Pipe); (5) deep pipe drains (Deep Pipe). The experiment was set out on a vertisol and our measurements were made during the growth of an irrigated onion crop.
Over the 3 months before the spring irrigations commenced, the perched water table on the Control was less than 400 mm below the soil surface for 27% of the time, whereas the shallow drainage treatments (Treatments 2, 3 and 4) reduced this time to less than 4%. During the irrigation season, the perched water table on the Mole + GES treatment rose above 400 mm for 3% of the time. The perched water table on the Mole treatment was above 400 mm for 14% of the time, compared with 19% of the time on the Control. The Deep Pipes were less effective in reducing the depth to the perched water table, both before and during the irrigation period.
Mole drains increased the gas-filled porosity above the drains. However, the gas-filled porosity remained below reported levels for optimum root growth. Although the drains effectively drained excess water, and lowered the water table, the hydraulic gradient was insufficient to remove all of water from the macropores. Gypsum enriched slots above the mole drains increased the gas-filled porosity in the slots but the drainable porosity in the undisturbed soil appeared to be inadequate for optimum root growth, even though some drainage occurred near the slots.
Discharge from the shallow drainage treatments averaged 58 mm for each irrigation, and was considerably more than the amount required to drain the macropores. The mole channels were in reasonably good condition at the end of the irrigation season, with at least 70% of the cross-sectional area of the channel open.
Shallow subsurface drains increased onion yield by about 38%. For each day the water table was above 400 mm, the yield declined by 0.23 tonnes per hectare. Farmer adoption of shallow subsurface drainage will depend on the long-term economic benefits (influenced by the longevity of the mole channels and yields response) and the need to develop more sustainable management practices. 相似文献
The mouldboard plough is the standard tillage implement used with animal power in Kenya. Various designs are currently used indiscriminately in varied soil types and conditions of operation. Their draught characteristics and comparative ability to achieve or maintain desired depths of operation under inherent edaphic conditions are unknown. The significance of variation in working speeds, when different species of draught animals are used, is also unknown. This study was therefore aimed at rating the performance of some common ploughs in order to advise farmers on optimisation of their use. Draught and vertical reaction (suction) on a per-tool basis were measured for four ploughs commonly used in the region; the Victory®, the Rumpstad winding-body® and two types of Rumpstad cylindrical-body® ploughs, using an instrumented rig. The experiments were in Pellic Vertisol, Ferralsol and Nitosol soils under two soil moisture conditions. Draught increased significantly with depth for all four ploughs, hence, regulation of tillage depth is paramount to avoidance of drastic fluctuations. Similarly, vertical reaction increased with depth of ploughing, which implies a more stable operation, hence, when draught can be sustained over an acceptable work duration, it is desirable to set the ploughs to work deeply. Significant speed–depth interactions were also recorded, and these imply that speed is important when operating depth is stochastic as is the case in the dynamics of these ploughs. Overall, the Victory plough had the lowest draught requirement (0.32–1.02 kN) under dry and moist soil conditions, hence, was the best option for use in areas represented by the three soil types in Kenya. Soil-type had a significant effect on mean draught and vertical reaction in the order (Draught, Vertical reaction); Vertisol (1.65 kN, 0.70 kN) > Ferralsol (0.66 kN, 0.44 kN) > Nitosol (0.64 kN, 0.01 kN), and Ferralsol (1.17 kN, 0.71) > Vertisol (1.09 kN, 0.23 kN) > Nitosol (0.49 kN, 0.11 kN) under moist and dry conditions, respectively. These results suggest that the duration of continuous work periods with draught animals should be based on soil-type. 相似文献
In Burkina Faso, significant amounts of endosulfan are applied to cotton fields; in addition, urban vegetable agriculture is often characterised by high fertiliser inputs, such as urban solid wastes containing heavy metals (e.g., Cu and Cd). Thus, the relevance of surrounding cotton and urban vegetable plots with vetiver (Vetiveria zizanioides) hedges to reduce environmental pollution by micropollutants was investigated using a leaching experiment, with outdoor lysimeters filled with two representative agricultural soils of Burkina Faso: Vertisol and Lixisol. After 6 months, little Cu was found in the leachates (< 0.010% of the applied amount) due to its high adsorption coefficient and its tendency to remain at the soil surface. Despite leachate and bromide recoveries being greater in soils planted with vetiver grass than in the bare soils, smaller amounts of endosulfan and Cd were found in the effluents from the planted soils (0.01% to 0.70% of the applied amount) than in those from the bare soils (0.01% to 1.48% of the applied amount), in agreement with their adsorption coefficients. These results may also be explained by a greater degradation of endosulfan in planted soils compared to bare soils and the absorption of Cd by vetiver. Thus, vetiver may decrease the risk of groundwater contamination, especially for Cd and endosulfan, which are more mobile than Cu. In addition, despite the smaller amounts of endosulfan and Cd measured in the Vertisol leachates (0.01% and 0.04% of the applied amount, respectively) compared to the Lixisol leachates, vetiver was more effective in decreasing the leaching of micropollutants if planted on Lixisol rather than on Vertisol. Further field monitoring is necessary to demonstrate the effectiveness of vetiver under the climatic conditions of Burkina Faso. 相似文献
A study was conducted for comparative evaluation of atomic absorption spectrophotometry (AAS) and inductively coupled plasma–optical emission spectroscopy (ICP-OES) for determining extractable zinc (Zn), copper (Cu), manganese (Mn), and iron (Fe) in sixty diverse soil samples having a wide range in pH and organic carbon (C). The results were significantly affected by the method of analysis and soil type but generally did not follow a definite trend. Results for extractable Fe in Alfisol samples were significantly greater when using ICP-OES than AAS; and the results for Zn, Cu, and Mn were not significantly different for the two methods. For Vertisol samples, the results for extractable Cu were significantly greater by ICP-OES than by AAS, whereas extractable Fe and Zn were significantly greater by AAS than by ICP-OES, and the results for Mn were not significantly different for the two methods. The results are discussed relative to soil type and differences in soil organic carbon and pH of the samples used in the study. 相似文献