Environmental Adaptability And Productivity Of Agroecological System In The Longdong Loess Plateau, China

As a typical rain-fed agriculture area, Chinese Loess Plateau of Eastern Gansu coexisted in a variety of agricultural systems in spatial-temporal variation. In this research, three research sites were selected from the south to the north according to the precipitation gradient. Their adjacent distances are about 110-130 km, and the differences of average annual precipitation are also about 110-130 mm representing the main precipitation range of Chinese Loess plateau. From 2006-2011, 150 households became the object of study (including mixed farm and cropping farm). Using the method of combining the field investigation and field experiments, detailed and continuous information of the households were obtained. On the basis of the natural environment and social environment of agricultural systems in Chinese Loess Plateau, this research analysis of the structure of agricultural systems, the coupling mechanism in energy and economic standpoint and the characteristics of their changes according to the precipitation gradient, labour supply and demand of agricultural systems, and discuss the environmental adaptability and productivity of agricultural systems.The main research conclusions are as follows:(1) With the increasing of annual precipitation, the planting structure changes from forage crops to grain crops, the degree of concentration for main crops increase, the fluctuation decrease, and the breeding scale decrease (P<0.05). In practice, the northern farmers by feeding of ruminant livestock, planting summer sown crops and perennial forages, deal with the challenges of low annual precipitation, seasonal and interannual differences. The southern farmers plant high value apple tree and grain crops in the limited cultivated land, and the income of crop production is as the main agricultural income. As the reason of straw feed livestock and manure to fertilizer the soil, the utilization levels of straw and manure of mixed farm are significantly higher than that of cropping farm (P < 0.05).(2) For crop production, the energy input per unit area of mixed farm is less than that of the cropping farm (P<0.05), with the increasing of annual precipitation, the amounts of input gradually increase, and the proportions of organic energy input to total energy input gradually decrease. The energy output per unit area of mixed farm is higher than that of crop farmers (P<0.05), with the annual precipitation increase, the amounts of output gradually increase, and the proportions of grain energy output to total energy output gradually increase. For livestock production, with the increasing of annual precipitation, energy input per sheep unit increasing, and the proportions of concentrate energy input to total energy input gradually increase while that of forage decrease. The energy outputs per sheep unit decrease. Energy utilization efficiency of mixed farm is higher than that of cropping farm (P < 0.05). For the farm, according to the energy coupling index of integrated farming system, energy coupling indexes of mixed farm are greater than that of cropping farm.(3) Adopting the standpoint of opportunity cost, the economic performance of the agricultural systems is analyzed. With the increasing of annual precipitation, farmers’ cash input and output from the livestock production conversion to crop production; the net cash income and cash efficiency decrease (P<0.05). In the same research site, the net cash income and cash efficiency of mixed farme are higher than that of cropping farm (P < 0.05). Mixed farm use more manure to fertilize the soil than cropping farm, to replace the use of some fertilizers (P<0.001), meanwhile use straw and forage to supply ration. Mixed farm not only benefits from system coupling in economic performance, but also conducive to avoid the economic loss caused by drought and enhance the sustainability of agricultural system. By deepen the system coupling, the income of agricultural production will sharply increase. For example, such as mixed farmers, the net cash income and cash efficiencyof the northern farmers are 3 times of the Southern farmers. The family income of mixed farm mainly depends on the sale of livestock products from sheep or goats. The family income of crop farmers is from non-agricultural activities. Compare family income after calculating income of non-agricultural activities: in the north, the family incomes of mixed farm are significantly higher than that of crop farm (P<0.05); in the middle, there are no significant differences of family income between mixed farm and cropping farm (P>0.05); in the south, the family incomes of mixed farm are significantly lower than that of crop farm (P<0.05). The farmers in research area face the choice of agricultural production mode.(4) The supply of farmers’ labour has the following characteristics: the elasticity between agricultural production and non-agricultural activities; the extensibility of working age; the age is old; the education level is low. The labour demand characteristics of crop production: with the annual precipitation increase, the farming operations are from the simple to the complex, changing from extensive to the intensive; the demand of labour per unit area significantly increase (P<0.05); seasonal fluctuation difference between the mixed farm and crop farm gradually decrease. The labour demand characteristics of livestock production: with the annual precipitation increase, farming operations reduce; monthly labour demand difference between the mixed farm and crop farm gradually reduce; the monthly labour demand of mixed farm reduce, and that of crop farmers remain stable trend. Monthly labour demand differences of mixed farm are smaller than that of crop farm. In the northern and middle sites, the labour supply and demand of agricultural production appears surplus and deficit alternately; in the southern site, labour supply and demand of agricultural production is surplus except September.(5) Livestock production plays a vital role in integrated farming system. Livestock provide manure to fertilize the soil reducing the excessive application of fertilizer and its environmental negative effect, draft to cultivate the land, and crop residues feed livestock promoting the energy cycle. Moreover, income from livestock may be able to buffer low crop yields in dry years. Livestock production provides meet and emergency cash to farmers, and improves agricultural system stability.(6) Using the coupling indicators of integrated crop-livestock production system, the coupling characters of energy and economic are analysed. The energy coupling of mixed farm mainly rely on internal interaction among each subsystems, and that of cropping farm mainly rely on energy flow exchange between the system internal and external. With the increase of annual precipitation, coupling intensity of livestock production to crop production is reduced, and the external economic dependence of farming system is enhanced.In short, the reasons of the ecological deterioration and the rural poverty in the Chinese Loess Plateau of eastern Gansu are unreasonable utilization of agricultural system. Adjustment agricultural structure through planting forage for raising livestock can optimize the allocation of productivity, and enhance the environmental adaptability. These provide the theoretical basis and practical reference for the succession of agricultural systems in Chinese Loess Plateau.