Effect of mulching & farm manure on water use efficiency, soil properties & crop growth while using brackish water for irrigation.

In many arid and semi-arid regions, use of brackish ground water has become necessary for irrigation to balance rapidly increasing water demands. Addition of organic material such as farm manure and crop residues would be useful in improving soils that are otherwise deteriorated when brackish water is used for irrigation. Keeping in view role of mulching and farm manure in ameliorating ill effects of brackish water, two years (2009- 2011) field studies were conducted to evaluate the effects of mulching (control, 25, 50, 75 and 100 % soil cover) and farm manure (control, 10, 20 and 30 Mg ha-1) on water use efficiency, soil properties and crop growth. A randomized complete block design with four replications was followed for laying out the experiments. Four field studies were conducted at the research farms of the College of Agriculture D. G. Khan, Sub Campus of University of Agriculture, Faisalabad. In Study-1, two experiments were conducted following cottonwheat rotation and in Study-2, two experiments were conducted following mung-wheat rotation. Crops were grown during their normal planting seasons, with recommended seed rate and planting methodology. These crops were irrigated with brackish water and measured amount of irrigation was ensured using cut-throat flume. Soil samples collected from 0-15, 15-30, 30-45, 45-60, 60-90 and 90-120 cm soil depth before sowing and at each crop harvest, were analyzed for EC1:5, pH, bulk density, N, P, K and organic carbon concentration. It was observed that the farm manure at 30 Mg ha-1 (FM4) and mulch at 7.6 Mg-1 ha (M5, 100 % SC) produced the maximum cotton, wheat and mung crop yield as compared to control. Whereas economic and marginal analysis indicates that FM4 gave more economical yield as compared to all other levels of farm manure and mulch during both of the years.\ud As for as soil properties were concerned more soil bulk density was found in controlled treatments while less was found in M5 and FM4. Infiltration rate significantly decreased in M5 and FM4 applied plots compared to control. Maximum EC1:5 was obtained in control, where as minimum value was obtained in FM4 (30 Mg ha-1) and M5 (100 % Soil cover). Maximum values of NPK and soil organic carbon (SOC) contents were observed at maximum level of mulching (M5) and farm manure (FM4) as compared to control. The highest values of NPK, SOC, EC1:5, SAR, pH, soil bulk density and salt accumulation was observed at upper soil depth compared to lower soil depth whereas percent increase was more in lower soil depths as compared to upper soil depths. Maximum water use efficiency was obtained in case of FM4 and M5 as compared to control. Minimum salt concentration were observed in case of M5 (100 % soil coverage was done) and FM3 (20 Mg ha-1). Root length density of wheat crop was more in M5 and FM4 as compared to control and in upper soil layers as compared to lower soil layers. It is clear from the results that manuring and mulching improves the water use efficiency, physical and chemical properties of soil, enhance the yield of cotton, wheat and mung crops and also helpful in ameliorating ill effects of brackish water on soil and crop characteristics