Planting Adaptation Comparison Between Sorghum And Maize In Farming- Pastoral Ecotone In The Semiarid Loess Plateau

The semiarid Loess Plateau area of China is a typical farming-pastoral ecotone, with the characteristics of low effective accumulated temperature and less precipitation which varies within years, not benefits for thermophilic crops growth, spring wheat is the most popular crop, water shortage is one of the major constraints to agricultural production. In recent years, plastic film mulching technique has been burgeoning among planting patterns, maize has become another main grain crop from catch crop in this region gradually, which expand the space of local agricultural management mode changes because of its grain and feeding use advantage; we try to introduce sorghum in local crop system based on the fact, which recognized with higher water use efficiency in C4 crops, aim to enhance the stability and sustainability of agricultural development. In traditional agriculture, sorghum also has a little planting, but not developed well and only use for straw forage grass, the planting acreage has been declining.In this paper, we compared adaptation of sorghum and maize under plastic film mulched and no mulched (bare) condition, with the objective to investigate the reasonable explanation of these two crops developmental differences and possibility of sorghum further development in local, try to explain whether plastic mulching technique can widely apply on C4 crop production, which with high temperature requirement, hope to improve the land first productivity in further, provide more choices for local combination of farming and grazing development mode. The field experiment was conducted at the semiarid ecosystem research station of Loess Plateau, Lanzhou University in April 2013 to November 2014, the annual precipitation was 314.09mm, four treatments were set up, plastic film mulched sorghum (MS) and maize (MC),no plastic film mulched sorghum (BS) and maize (BC),compared and analyzed the yield, soil moisture, water use efficiency, soil organic carbon, total N, total P, recovery efficiency of N and P, economic benefits, linear programming and planting pattern also has been done.The results showed that plastic film mulching increased corn grain yield significantly, but sorghum grain still not mature in same condition, although as C4 crops as corn.2013 (MS) and (BS) aboveground biomass (dry matter, include grain) were up to 10329.37 kg·hm-2and 9461.78kg·hm-2, higher than MC and BC 79.16% and 146.16% respectively (p<0.05), but lower much than maize in 2014,which was planted with low density, biomass decreased significantly; In terms of resources, sorghum consumed more deeper layer(1.0-2.0m)soil water and soil moisture of sorghum farm land in 0-2.0m layer was significant lower than maize in both beginning and the end of growth period (p<0.05); water use efficiency, nitrogen recovery efficiency and phosphorus recovery efficiency of sorghum was much higher than maize in 2013, but these three items were all lower in 2014;Soil organic carbon(SOC) and total nitrogen(TN) were negative balance within experimental period, MS and BS were significantly decreased more than the total amount of MC 30.43% and 38.09% respectively, there was no significant difference in same treatment of organic carbon,but the mulched was significantly reduced than that of no mulched treatment, total phosphorus was positive balance, MC was increased most, followed by BC, MS and BS; there was no obvious advantage on economic benefits has been showed within two years experimental period, this may be the main reason of sorghum has not been developed well in the area.This shows that although high density planting sorghum in ecological benefits including the aboveground biomass, water use efficiency, nitrogen fertilizer recovery efficiency and phosphorus recovery efficiency were significantly higher than maize, there was no obvious advantage of economic benefits has been showed, while in low density planting pattern, sorghum ecological and economic benefits was significantly lower than maize (p<0.05), so no economic advantage may be the main reason for sorghum has not been developed well in the area, plastic film mulching also cannot make sorghum mature, so the productivity performance and adaptation needs further research.