On-Farm Evaluation oF Land Treatments to increase Infiltration and Crop Yield on a Shallow vertic soil

An on-farm experiment was conducted on a Vertic Inceptisol site with a 2% slope at Chevella watershed, Medak disrrict (Andhra Pradesh), lo compare the effect of three land treatments: (i) graded contour cultivation ort 0.2% gradient.........

Soil management and production of alfisols in the semi-arid tropics. IV. Simulation of decline in productivity caused by soil erosion

Maintenance of a productive soil base by minimizing soil erosion is vital to long-term crop production. In this study, a modelling approach is used to estimate the effects of soil erosion on productivity for a sorghum cropping system on an Alfisol in the semi-arid tropics of India. Predictions of erosion, runoff and yield decline due to erosion, for variations in initial soil depth, slope, tillage strategy and amendment treatment, are presented. On average, soil depth decreased by 0.91 cm/year at Hyderabad for a 10% slope, 80 cm initial soil depth, shallow tillage at planting and no surface amendment. Rates of soil removal and subsequent yield decline were higher for shallower soils, steeper slopes and if management practices provided less surface cover during the crop. The productive life of the soil was less than 91 years for some soil depths, slope and management combinations. For other combinations, significant yield decline was predicted after 91 years of cropping. The quantification of erosion-productivity relationships allows us to identify regions with a higher risk of degradation from soil erosion and to estimate the impact of various management options on long-term sustainability. Models provide a basis to focus research and a means of assessing alternative management strategies to preserve long-term production

Soil management and production of alfisols in the semi-arid tropics. III. Long-term effects on water conservation and production

A calibrated cropping systems model was used to provide long-term biophysical responses of various land managements at two differing semi-arid tropic environments in India. Organic based practices such as farmyard manure or straw amendments and perennial pastures reduced runoff by between 50 and 87%, and are optimum for in situ, water and soil conservation. A consequence of the reduced runoff was an increase in drainage below the root zone. Furthermore, the detrimental effects of cropping on high slopes and long slope lengths showed that it is not feasible to crop on slopes greater than 5%. Our study did not incorporate farmer preferences for land management, but the results can still be used as an integral part of decision making for optimum land management

Soil management and rroduction of alfisols in the semi-arid tropics. I. Modelling the effects of soil management on runoff and erosion

Techniques to simulate effects of surface cover and tillage on runoff and erosion are described. Data for 15 soil management treatments on an Alfisol in the semi-arid tropics, India, were used to modify existing procedures of runoff prediction using USDA runoff curve numbers. A relationship between surface cover and curve number was developed to account for the effects of surface cover on runoff. Impact of shallow or deep tillage was predicted using functions that relate curve number to cumulative rainfall since tillage. The derived relationships were applied to adjust curve number due to the effects of cover and tillage on a daily basis and were incorporated into the cropping systems model called PERFECT-IND. Results of model validation showed that PERFECT-IND explained between 71 and 91% of the variation in daily runoff volumes. The model also provided accurate predictions of average annual runoff ranging from 33 to 217 mm for the 15 soil management treatments. Runoff was reduced to a much greater extent by surface cover compared with surface roughness. Surface cover reduced runoff curve number by a maximum of 35 units. The maximum reduction in curve number due to surface roughness was 5 units for shallow tillage and 10 units for deep tillage. Erosion predictions were acceptable but the lack of erosion data for all years in the experimental data limits the confidence in model output. Model calibration and validation have provided a set of parameters that can be coupled with historical climate records to provide a long-term perspective of the effects of soil management on runoff and erosion. Keywords: simulation, model, runoff, water balance, curve number

Soil Management and Seasonal Community Structure of Soil Microarthropods in Semi-Arid Tropical Alfisols

Response of the soil microarthropod community was monitored across different soil management treatments with annual and perennial crops in semi-arid tropical Alfisols. Annual crop management treatments included zero, shallow and deep tillage either bare, or with application of 15 t ha" farm-yard manure or 5 t ha" rice-straw. Perennial crop treatments were Stylosanthes hamala, Cenchrus ciliaris and pigeonpea either alone or in combination. Microarthropods, across all the treatments, included Collembola, Acarina, Araneae, Pseudoscorpiones, Pauropods, Symphyla, Diplura, Dermaptera. Psocoptera, Isoptera, Thysanoptera, Homoptera, Hymenoptera and Coleoptera adults and larvae. The number of Collembola and Acarina together constituted > 62% of the total microarthropods. The population densities of all microarthropods showed a more or less similar pattern of temporal variations under all treatments. They were higher during the rainy season of 1990 and 1991 in bare plots under zero-tillage treatment followed by plots under rice-straw treatment. However, densities during rainy months of 1989 were low compared to those of 1990 because of the high dose of carbofuran treatment. Population densities showed significant treatment differences during some months indicating significant impact of soil management practices on microarthropod community structure

Effect of Soil Management Practices on Runoff and Infiltration Processes of Hardsetting Alfisol in Semi-Arid Tropics

Alfisols oi Semi-Arid Tropics (SAT) are often chiiractcriscd as structurally unstable (EL-Swaify et 31.. 1905). Under the impact of raindrops the structural instability leads to formation of a seal on the surface. The surface seals rcducc infiltration and increase runoff (Moore, 1981 1. As a result, plant-available water in the profile gets reduced. In most of the SAT Alfisols crop yields arc constrained by the plant-available water

Surface crusting as a constraint to sustainable management on a tropical Alfisol: I. Soil physical properties

Physical properties related to crust formation were assessed on a clayey-skeletal, mixed, isohyperthermic Udic Rhodustalf in India. A critical proportion (30 to 40%) of fine-textured fractions, particularly silt, appeared to be important in structural crust formation due to aggregate breakdown, rainfall compaction, and particle rearrangement of the surface soil. Significantly higher water dispersible clay percentage (7.1%) and dispersion ratio (0.34) at 60 days after planting (DAP) indicated diminished structural stability and increased slaking tendency of surface aggregates. Infiltration rates decreased by 40 to 60% in tilled bare systems from 0 to 60 DAP. Termite activity appeared to increase cumulative infiltration and steady state infiltration rate although additional research is required to determine the precise nature of its influence on porosity and pore continuity. Soil cover and biological components may be manageable factors to improve soil structure and stability, as well as to reduce crusting and its associated adverse effects in the semiarid tropic

Soil management of alfisols for water conservation and utilization

Alfisols are abundarrt soils used for rainfed agrkulfure but have a wide rarrse of problrrtrs due lo lora irrfilfratiorr rates. We studied a ranse of soil and crop managemenl options (fillngc and muklring for anrtunl crops, a~rrl ~wrerrninl crolrs) t:, incrcase infiltration during 1989 and 1990. With annual crops sfraw ~rrul~.ahn d FYM trrulch reducrd runof by 52% ar~d1 7% reslwcfitrly compared to barc freatmenfs but tillage h d small and inconsislent effecfs. Perennial crops produced high rutaolf duritrg the esfahlisl~~rrepnetr iod in 1988 and sukquetrfly a wide range of response depending or1 flu foliage slructure of fire r.roj>. Tall groroirtg pererrnial pigeon pea did not reduce runoff compared lo crops with no surface amendment but llrc derrse, shorf, s~rrtrulitrg stylosarrthes harr~ata reduced runofl more than straw mulch. Reduction in runof will decrease soil erosion and nrny increme draitra~e by up to 200 nrm pcr year. This drainage is a mmsive potential resource for dcrp rooted crups or irrigation fro111 grou~ritiuafer. Sustairrnble agrkultural production a1 a wntershed scale will involve soil manageme71t lo increase irtftltrafion in rairrfed areas and exploitafion of cortscqurnt increases in groundwater resources by irrigation or deep roofed crops

Soil management options to reduce runoff and erosion on a hardsetting Alfisol in the semi-arid tropics

Improved farming systems are needed to enhance productivity and reduce degradation on hardsetting Alfisols in the semi-arid tropics. A long-term experiment was started in July 1988 at ICRISAT, Hyderabad, India, to evaluate practices to improve infiltration and reduce erosion by stimulating biological activity and protecting soil in the rainy season. This paper outlines the rationale for the experiment, describes it, and summarises early results. Fifteen treatments in a randomised block design were applied to plots 28.5 m long by 5 m wide on a 2% slope. Nine annual treatments made up a factorial sub-set: tillage by tined implement to three depths (0, 10 and 20 cm) combined with three mulch treatments (no mulch, farmyard manure (FYM) at 15 t ha−1, and rice straw at 5 t ha−1). Pearl millet (Pennisetum glaucum) was sown in the factorial sub-set in July 1988. Six perennial species ley treatments (combinations of perennial pigeonpea (Cajanus cajan), verano stylo (Stylosanthes hamata), and buffel grass (Cenchrus ciliaris)) completed the randomised block design. All treatments were replicated three times making 45 plots in total. Plots were instrumented to measure runoff and soil loss. Millet straw yield was reduced by tillage to 20 cm and grain yield was significantly reduced by tillage to both 10 and 20 cm. Mulches had no effect on millet straw yield but FYM significantly increased millet grain yield. The proportion of rainfall running off plots ranged from 15.8 to 39.1%. Perennial species treatments tended to have higher runoff than treatments under millet, but this was not consistent as zero tillage without mulch, and tillage to 10 cm either with mulch or with FYM mulch, also had relatively high runoff. Rice straw mulch significantly reduced runoff by comparison with FYM and no mulch. Soil was lost mainly as suspended load, indicating that raindrop detachment was the main erosion process. Effects of perennial species were variable and probably reflected the degree of surface protection provided in this establishment phase. Tillage significantly increased suspended load concentration in the first major runoff event but not in an event later in the season. Rice straw mulch significantly reduced bed load concentration in the first event and reduced suspended load in the later event. The ability of straw mulch to reduce runoff volume and sediment concentration suggests mulch-based systems may be able to contribute to sustainability of farming systems in the semi-arid tropics. The lack of beneficial effects from tillage suggests a limited role for tillage-based systems. Results from subsequent years are needed to form definite conclusions and to show effects of slower biologically-induced changes in the soil