The Farmland Ecological Effects And The Crop Yield-Increasing Mechanisms Of Different Mulching Materials

Both pot experiments and field experiments were employed with completely random design and completely random block design to study the farmland ecological effects and the crop physiological effects and yield-increasing mechanism of different mulching treatments with straw (SM), plastic film (PM), mat (MM), cardboard (CM), (weaving) bag (BM), and garbage (GM). The results showed that all of the experimental mulching materials increased the yields of crops to a certain degree. The corn yields in treatment SM were the highest and reached 8 666.7 kg hm-2 and 8 322.2 kg hm-2, and in CK were the lowest and only attained to 7 255.6 kg hm-2 and 6 988.9 kg hm-2 in the 2 year field experiments. The corn yields in the treatments of SM, PM, MM, CM, BM, and GM were 19.4% and18.8%,17.2% and 15.3%,16.1% and 15.7%,13.3%,12.1%, and 2.7% more than that in CK separately,and the corn yields in treatments of SM, PM, MM, and CM were significantly higher than that in CK, but in treatments of BM and GM were not. The corn yields only in treatments of SM and MM were significantly higher than that in CK in the pot experiment. The increases of corn yields in different mulching treatments were due to their effects on the differentiation of corn female ear, but not on the corn seed weight. The treatments of SM, PM, and BM also increased spring wheat yields to varying degrees in the field experiment. The spring wheat yields in treatment PM were 33.7% and 43.6% higher than that in CK with and without irrigation respectively, and the significantly higher yields were due to the extremely high spikes per unit area in treatment PM. The spring wheat yields in treatments of SM and BM were 18.4% and 13.5% higher than that in CK without irrigation respectively, and it was due to the significantly high seeds per spike and significantly high seed weight in treatments of SM and BM. Irrigation decreased the differences between the spring wheat yields in treatments of SM, BM, and PM and that in CK, and even made the differences between the yields in treatments of SM and BM and that in CK from significant to no-significant. It proved the importance of mulching cultivation in the rain fed agriculture. The effects of different mulching materials on crop yields were mainly due to their effects on soil environments and then the improvement on the growth and development of crops. The significantly temperature increasing effect of plastic fielm was not matched by any other experimental mulching materials, even though the treatment BM increased soil temperature to a certain degree. The temperature decreasing effect of plant mulching materials, such as straw, mat, and cardboard, in high temperature season and the thermal insulation effect of straw in low temperature season were not matched by plastic film and other experimental mulching materials. The water retaining effects of plant mulching materials, such as straw, mat, and cardboard, were similar to that of plastic film and even stronger than that of plastic film especially in the low part of soil profile both in crop growth season and in the winter season. Based on that fact, the thought of "the drought in spring should be fought in the former winter"was advanced. It proposed that in the drought and semi-drought area of the North China, we should not only pay attention to taking drought-relief measures in spring when drought comes and maintaining soil moisture by mulching in crop growing period, but also to the soil moisture restoration and maintenance in winter, which can lay a good foundation for fighting drought in the coming spring. Using straw and other plant materials to mulch in winter is an economical and practicable drought-relief measure. The regression isogram is a good method for describing and analyzing the differences of the temporal and spatial distribution of soil moisture among the different mulching treatments. Plant mulching materials, especially straw and garbage, significantly improved soil fertility, but plastic film and bag mulching caused soil organic matter and nutrients contents decreasing. Straw, plastic film, mat, bag, and garbage mulching increased soil microorganisms in quantity to varying degrees, but cardboard mulching decreased soil microorganisms, especially fungi and bacteria, because of its strong alkalinity. The increasing ranges of soil microorganisms in different experimental materials mulching treatments were bigger in lower soil moisture condition than in higher soil moisture condition. Too much soil water especially affected the soil microorganisms in treatment PM. According to the effects on the crop growth progress, crop growth condition, leaf area index of crop population, crop net photosynthesis rate, crop dry matter accumulation, relative growth rate, and assimilation rate, treatments of PM, SM, and MM had the relatively higher improvement effects on crop growth and development, but the improvement effect of treatment PM mainly appeared in the earlier stage of crop growth, and the improvement effects of treatments of SM and MM mainly showed in the middle and later stage of crop growth. The improvement effects of treatments of BM, CM, and GM on crop growth and development were limited or not significant. Thus it can be seen that different mulching materials have different environmental effects and these...