Effect of cyclic use and blending of alkali and good quality waters on soil properties,yield and quality of potato,sunflower and Sesbania

Degradation of soils through the use of alkali waters constitutes a major threat to irrigated agriculture especially for the cultivation of sodicity sensitive crops. The response of potato (Solanum tuberosum), sunflower (Helianthus annus) and Sesbania (Sesbania sesban) green manure to the combined use of a good quality canal water (CW, ECcw 1.1 dS/m, RSC nil, SAR 1.8) and an alkali water (AW, ECaw 3.6 dS/m, RSC 15.8 me/L, SAR 12.4) was evaluated for 5 years (1998–2003) on a well drained sandy loam soil (ECe 2.5 dS/m, pH 7.9, exchangeable sodium percentage, ESP 5.3). Increase in soil pH (8.9–9.1), salinity (4.7–5.1 dS/m) and sodicity (ESP 25–41) as a consequence of irrigation with alkali water affected the growth and yields of all the crops. The sustainability yield index (SYI) when irrigated with AW was 0.063 and 0.133 for potato and sunflower, respectively, indicating that these crops should not be irrigated with such high alkalinity waters. Cyclic use treatments included alternating irrigations with CW and AW, with CW to start with (1CW:1AW), alternating two irrigations each with CW and AW and applying CW to start with (2CW:2AW), alternating two irrigations each with CW and AW and applying AW to start with (2AW:2CW), four irrigations with AW to start with and followed by two with CW (4AW:2CW) and crop-wise alternations of CW and AW, with application of CW to potato and AW to sunflower (CWp:AWs). The SYI of potato improved to 0.703, 0.642, 0.442 and 0.579, respectively with the cyclic 1CW:1AW, 2CW:2AW, 2AW:2CW and CWp:AWs treatments. The values of SYI were 0.633 and 0.415 for potato when irrigated with blends of CW and AW in the ratio 2:1(2CW:1AW) and 1:2 (1CW:2AW), respectively. Similarly, the SYI for sunflower ranged between 0.481–0.736 and 0.512–0.592 for cyclic use and blending but was reduced to 0.394 with 4AW:2CW in cyclic use mode. When averaged for 5 years, the relative yields (compared to CW) ranged between 65–85 and 61–94% for cyclic use in potato and sunflower, respectively. However, the values ranged between 66–83 and 71–81% for blended waters. Considerable deterioration in produce quality was observed in terms of potato grade and weight loss on storage as well as the smaller seeds along and lower oil content in the case of sunflower. The overall deterioration in soil properties under different modes was related to the proportions of AW applied. Computations further indicated that with a similar proportion of CW and AW, cyclic application CW during the initial stages would minimise the adverse effects of alkali water.     

Effects of winter wheat row spacing on evapotranpsiration, grain yield and water use efficiency

A field study was conducted from 2002 to 2007 to investigate the influence of row spacing of winter wheat (Triticum aestivum L.) on soil evaporation (E), evapotranspiration (ET), grain production and water use efficiency (WUE) in the North China Plain. The experiment had four row spacing treatments, 7.5 cm, 15 cm, 22.5 cm, and 30 cm, with plots randomly arranged in four replicates. Soil E was measured by micro-lysimeters in three seasons and ET was calculated from measurements of soil profile water depletion, irrigation, and rainfall. The results showed that E increased with row spacing. Compared with the 30-cm row spacing (average E = 112 mm), the reduction in seasonal E averaged 9 mm, 25 mm, and 26 mm for 22.5 cm, 15 cm, and 7.5 cm row spacings, respectively. Crop transpiration (T) increased as row spacing decreased. The seasonal rainfall interception and seasonal ET were relatively unchanged among the treatments. In three out of five seasons, the four different treatments showed similar grain yield, yield components and WUE. We conclude that for winter wheat production in the North China Plain, narrow row spacing reduced soil evaporation, but had minor improvements on grain production and WUE under irrigated conditions with adequate nutrient levels.     

Effect of mulching on soil and plant water status, and the growth and yield of wheat (Triticum aestivum L.) in a semi-arid environment

Mulching is one of the important agronomic practices in conserving the soil moisture and modifying the soil physical environment. Wheat, the second most important cereal crop in India, is sensitive to soil moisture stress. Field experiments were conducted during winter seasons of 2004-2005 and 2005-2006 in a sandy loam soil to evaluate the soil and plant water status in wheat under synthetic (transparent and black polyethylene) and organic (rice husk) mulches with limited irrigation and compared with adequate irrigation with no mulch (conventional practices by the farmers). Though all the mulch treatments improved the soil moisture status, rice husk was found to be superior in maintaining optimum soil moisture condition for crop use. The residual soil moisture was also minimum, indicating effective utilization of moisture by the crop under RH. The plant water status, as evaluated by relative water content and leaf water potential were favourable under RH. Specific leaf weight, root length density and dry biomass were also greater in this treatment. Optimum soil and canopy thermal environment of wheat with limited fluctuations were observed under RH, even during dry periods. This produced comparable yield with less water use, enhancing the water use efficiency. Therefore, it may be concluded that under limited irrigation condition, RH mulching will be beneficial for wheat as it is able to maintain better soil and plant water status, leading to higher grain yield and enhanced water use efficiency.     

The influence of different Acacia senegal agroforestry systems on soil water and crop yields in clay soils of the Blue Nile region,Sudan

The purpose of this study was to test the hypotheses that (1) the tree Acacia senegal competes for water with associated agricultural crops, and the soil water content would vary spatially with tree density and type of management; (2) the microclimate created by trees would favourably affect the soil water content and improve the growth of associated agricultural crops. Trees were grown at 5 m × 5 m or 10 m × 10 m spacing alone or in mixture with sorghum or sesame. Soil water content was measured using a neutron probe at three depths, 0–25, 25–50 and 50–75 cm; and at different stages of crop development (early, mid, and late). Crop growth and yield and the overall system performance were investigated over a 4-year period (1999–2002). Results showed no significant variation in the soil water content under different agroforestry systems. Intercropping also resulted in a higher land equivalent ratio. No significant variation was found between yields of sorghum and sesame when these crops were grown with or without trees. The averages crop yields were1.54 and 1.54 t ha⁻¹ for sorghum; and 0.36 and 0.42 t ha⁻¹for sesame in intercropping and pure cultivation, respectively. This suggests that at an early stage of agroforestry system management, A. senegal has no detrimental effect on agricultural crop yield. However, the pattern of resource capture by trees and crops can change as the system matures. There was little competition between trees and crops for water suggesting that in A. senegal agroforestry systems with 4-year-old trees the clay soil has enough water to support the crop growth over a whole growing season up to maturation and harvest.