Role of tractors, tubewells and plant breeding in increasing cropping intensity in Pakistan's Punjab
研究了巴基斯坦旁遮普省棉花-小麦区种植强度低于潜力和印度旁遮普省的原因，发现灌溉用水是主要限制因素，拖拉机作用较小，而缺乏适合双季作的品种也制约了种植强度，政策应改善供水并促进早熟品种研发。
Cropping intensity in the cotton-wheat areas of Pakistan's Punjab is well below its potential, and also significantly lower than in neighbouring areas of India's Punjab. Analysis of annual cropping intensity indicates that access to irrigation water is the major factor explaining differences in cropping intensity in a cross-section of farmers. Ownership of a tractor plays a lesser role in increasing cropping intensity, although official credit policy has emphasized tractorization over investments in tubewells. Analysis of season-specific cropping intensity also indicates that lack of appropriate varieties for double cropping also constrain cropping intensity. It is estimated that cropping intensity could be increased by at least 30% through policies directed at improving water supplies and by promoting research on earlier varieties of cotton, maize and oilseeds.