Minimal irrigation on small agricultural watersheds with red soils in the semi-arid tropics of Andhra Pradesh, India
Abstract Part of the runoff water from sloping red soils of the Andhra Pradesh region was stored and used for local irrigation of several crops over several years, during which rainfall varied widely in the cropping period. This type of utilisation of harvested water is unique in the semi-arid tropics. Judicious application of small amounts of water through alternate central furrows to wet the root zone during a stress period increased yields significantly. Response to irrigation decreased with increasing soil moisture in the root zone. Irrigation was beneficial in both sub-normal and normal rainfall conditions during the cropping period. With above normal rainfall there was hardly any need for irrigation. According to rainfall probability, expected yield increases of sorghum and castorbean over time were on average 251 and 523 kg/ha with irrigation of only 15 and 50 mm, respectively. With only 20 mm of irrigation in a cropping cycle consisting of pigeonpea/pearl millet-cowpea or horsegram, gross yields increased significantly. Vegetables, hitherto grown under open well irrigation only, were irrigated using pond water. Vegetable yields increased significantly with irrigation. A ground cover of pulses to prevent soil erosion during post-monsoon storms could be maintained with minimal irrigation still giving some fodder yield.
Effect of deep tillage on dryland crop production in red soils of India
Abstract The red soils of the semi-arid tropics of Andhra Pradesh, India, are shallow, eroded and compact. The profile is anisotropic with a dense sub-surface layer. The average depth of the surface layer is 8.2 cm. The solum depth varies from 50 to 100 cm. The subsurface layer restricts the root proliferation of crops. A light wooden country plow is used by farmers for primary tillage. It penetrates on average to a depth of 15.5 cm with a coefficient of variation of 80%. To disturb the sub-surface layer to a greater extent a heavy-duty disc plow was used. This tilled to a depth of 23.3 cm, with a coefficient of variation of 29%, and reduced the bulk density. The infiltration and depth of penetration of the wetting front increased considerably with deep tillage. The advantage of deep tillage to crop yields was found to be dependent on rainfall pattern and plant type. The interaction was between recharge in the profile and rooting depth. In a normal rainfall season the yield advantage was observed for both short duration (sorghum and pearl millet) and long duration (castor) crops, while the advantage in an above-normal rainfall season was restricted to long duration crops only. No yield advantage was noticed in a sub-normal rainfall year for any of the crops. The residual effects of deep tillage were marginal. Therefore, by considering the historical rainfall data, it was observed that deep tillage was beneficial in 63 and 91% of years for short and long duration crops, respectively. Adoption of deep tillage every year in traditional castor—sorghum rotation resulted in benefits in 56% of years for both the crops. Since deep tillage requires a high monetary input, it is advisable to adopt this practice only for castor. This illustrates clearly the need for considering rainfall pattern and crop requirements to select an appropriate tillage practice under rainfed farming.
Effects of deep tillage and profile modification on soil properties, root growth, and crop yields in the United States and Canada☆
Abstract Unfavorable conditions of soil profiles, through their adverse effects on the growth, proliferation, and activity of roots, may severely limit the yield of crops at some locations in the United States and Canada. A review of the literature showed that deep tillage and modification of soils having unfavorable profiles may increase crop production by providing larger, more favorable zones of soil for the growth, proliferation, and activity of roots. The improved conditions may result from disrupting dense, high-strength horizons; leaching or burying salts or toxic materials; increasing the capacity of sandy soils to retain water; and reducing the erodibility of soil. When the horizons causing problems were adequately disrupted or altered, yields of crops were generally increased. Benefits from the treatments were greater when precipitation or irrigation were limited than when they were adequate. There are many soils on which no benefits can be expected from deep tillage and profile modification.