中国粮食作物种植结构调整及其水土资源利用效应

The adjustment of China's grain cropping structure and its effect on the consumption of water and land resources

粮食种植结构调整会影响农业资源的消耗需求。20世纪90年代中后期以来,玉米在我国粮食生产中的地位明显提升。以粮食种植结构无调整为参照情景,一定产量下,1996-2015年,在国家层面,因粮食种植结构调整对水土资源消耗的节省量约占现期需求量的4%左右。在区域层面,从结构调整对种植面积的减省效应看,耕地资源相对丰富的北方地区明显高于南方地区;从对水资源消耗的减省效应看,北方贫水区也普遍高于南方地区,干旱度最高的西北地区最高。期间区域分品种粮食生产广泛受到作物种植比例变化的影响。研究结果表明,要充分利用好南方水热资源,恢复水稻生产,主要取决于稻米需求及其种植效益,而北方地区则要尽可能按降水规律调整农作制度,合理控制水稻、小麦的种植面积。

Estimation of the effect of grain production adjustment on the consumption of water and land resources will help to formulate the strategy for sustainable agricultural development.Since the mid and late 1990 s,the proportion of corn in China’s grain production has been obviously improved.Taking grain cropping structure without adjustment as the base scenario,and under certain grain output,the actual grain production adjustment in China during 1996-2015 has brought about the savings of water and land resources,accounting for about 4.2%and 3.7%of current demand in grain production respectively.The adjustment of grain production comes from grain demand structure change,which helps to alleviate the consumption pressure of water/land resources in grain production to some extent,though China’s dietary transformation requires more agricultural resources.At the regional level,from the effect of structural adjustment on the demand for planting area,the savings in northern regions with relatively abundant arable land resources are significantly higher than those in the south.The area saving effect is higher in the northeast and northwest regions,and the least in southeastern coastal areas.From the effect of structural adjustment on the demand for water resources,the savings in northern regions are generally higher than those in the south,the highest in the northwest region with the highest drought degree,and the water saving effect in the middle and lower reaches of the Yangtze River is minimal.During the period,the output of regional grain crops has been widely affected by the change of cropping proportion,which is the indicator of the planting benefit and implies the change of consumption demand.Feed grain demand has increased more than rice and wheat rations,making the northern region suitable for corn planting become China’s main grain production area.In the southern rice region,the demand for rice is relatively limited,and the regional production advantages of wheat,corn and soybeans are also lacking,which causes the relative stagnation of grain production in the south.To this end,in southern China,the recovery of grain production and full utilization of the potential of water/heat resources mainly depend on the consumption demand for rice and farmers’planting benefit.For the northern region,in order to reduce the amount of groundwater irrigation,it is necessary to rationally control the cropping area of rice and wheat and to adjust farming system according to the law of precipitation as far as possible.