MULCHING; A TECHNIQUE TO CONSERVE SOIL MOISTURE

Pakistan falls in the arid to semi-arid climatic region of the world. Potential evapo-transpiration is considerably higher as compared to rainfall received. High temperature promotes capillary movement of salts upwards causing deposition of salts on the soil surface. The country has one of the largest contiguous irrigation systems in the world, irrigating over about 17 million hectares (Mha), and accounting for 90 percent of the agricultural production in the country. Even then, the existing canal supplies are insufficient to meet the crop water requirements. Increased pressure of population has catalysed the need to bring more area under cultivation to fulfill the food and fiber demands. To bring more area under cultivation or increase in cropping intensity, some additional water is required, but under the existing situation one of the alternative is the exploitation of the groundwater reserves, the whole quantum of which cannot be used as such because of poor water quality characteristics. The poor quality water can be used for irrigation of salt tolerant crops/tree species by adopting appropriate techniques. Thus to tackle this problem in the present scenario a sustainable solution is required by adopting moisture conservation techniques.
For arable soils, the most effective conservation practices for reducing surface evaporation are those that provide some degree of surface cover for the soil. A cover can be best provided by mulches or by tillage practices that leave plant residues on the soil surface. Mulch is any material placed on a soil surface for the purpose of moisture conservation or controlling weeds. It act as barriers to movement of moisture out of the soil. They can be either natural (eg. straw, wood chips, peat) or man-made (eg. transparent or opaque plastic sheeting). Mulches can also enhance soil temperature, depending on the type of mulch being used. In addition to reducing evaporation, vegetative mulches can reduce the spread of soil borne diseases, prevent weed growth, reduce soil erosion, provide nutrients, and enhance organic matter status of soil and aid in infiltration. Mulches improve infiltration by protecting the soil surface from the impact of raindrops and eliminating soil crusting. Mulches can however, be expensive and labour intensive to obtain, transport and apply to the soil. Mulching is usually more practical for high value crops such as vegetables and berries. Specially prepared plastics can also control evaporative loss. These types of mulches are often applied by machinery and there are holes or slits present for plants to grow through. These mulches are commonly used for vegetable and small fruit crops. Thus mulching not only improve the soil physic-chemical properties of soil but also improve water use efficiency of crops