Study On Ecological Optimization Of Farming System In The Farming-Pastoral Zone Of The Songnen Plain Under Global Climate Change

In this research, optimal farming systems were studied under ecological rules, and with which to resolve problems in the farming-pastoral zone of the Songnen plain under global climate change. Based on the statistical analysis of long-term climate data and field experiments, several conclusions were made:(1) It is a common practice that prepare seedbed in the early spring in farming-pastoral zone of the Songnen plain, however, spring seedbed preparation increases soil evaporation because of the occurrence of gale and low precipitation in this season, resulting in decreased soil water content and serious wind erosion. Results showed that spring seedbed preparation should be replaced by autumn seedbed preparation. The date of seedbed preparation should be postponed after 25th April in spring, if seedbed preparation could not be conducted in autumn.(2) Because the climate changed significantly under the background of global climate change, which showing as advanced beginning of growing season, postponed end of growing season, extended length of growing season and increased accumulated temperature in farming-pastoral zone of Songnen plain, the late-maturing and medium late-maturing varieties could be substituted as medium late-maturing and medium-maturing varieties respectively in this region. Or plant the same varieties but advancing or postpone the sowing dates according to the climate in spring. Sowing date could be postponed if low precipitation and gale occurred during the traditional sowing period. However grain production might be decreased if sowing date is late than end of May. Sowing date could be advanced,if sowing date is on 10th April, the seeds had better be germinated under 10℃before sowing. If sowing date is on 20th April when temperature is high, the seeds had better be germinated under 25℃before sowing. All the corns sowed on the furrow sown system in advance reach high production.(3) As quantitative evidence of global climate change continues to be identified, the potential impacts to regional and localized temperature and precipitation patterns are becoming apparent, and may promote significant changes to vegetation, both in terms of diversity and density. These conditions also affect agricultural crops which are highly influenced by seasonal weather patterns. With shifts in rainfall and temperature in Northern China, the occurrence of droughts during the growing season has become more likely. The conventional ridge sown tillage procedure has been challenged by water deficits in semiarid areas. These results suggest that moving seeds from ridges to furrows can increase corn yield directly by enhancing soil moisture, and indirectly by stimulating the growth of resource-capturing organs (leaf and root). Also, the furrow sown system causes less soil disturbance, thus reducing soil erosion and maintaining valuable cropland which is increasingly vulnerable to climatic and anthrogenic changes(4) The row space of corn field always maintains at 65cm in farming-pastoral zone of Songnen plain, resulting in relatively low production. Our experiments showed that 98cm of ridge distance with double row increased corn production in all experimental years, indicating adjustment of row space could benefit to the corn production. Large increase of corn production with 130cm ridge distance happened in rainy year, and less increase happened in arid year. The production with 43cm ridge distance treatment was slightly higher than traditional ridge distance. The allometry theory was used to explain how crops response to the heterogeneous environment resulted from the adjustment of row space. Our results showed that height, leaf area and leaf biomass was true plasticity, and stem biomass was apparent plasticity for year and row space treatments. Root biomass was true plasticity for year. Root biomass was apparent plasticity for row space treatments. The allometric exponent of height, leaf area, leaf and root biomass for 98cm treatment was more than those of the others.(5) In farming-pastoral zone of Songnen plain, the conflict of grass supply and livestock demand is serious. Green corn stalk is considered as available forage under the condition of no effect on yield, whose utilization for livestock could help to decrease the grazing pressure on grassland and also ensure plenty of high quality forage supply. The result is that three detasselled and deleaved 1-3 the top of leaves treatments for corn planting in narrow row space can increase yield in comparison with not detasselled and deleaved treatment of conventional row space, it also can produce more green corn straw with high content of crude protein and digestibility, and more metabolizable energy. Yield of detasselling and deleaving 1 tip leaf treatment was higher than that of contrast treatment and obtain corn straw with high content of crude protein and the digestibility when planting corn with the conventional row space. Deleaving time is significant to effect on corn yield, but deleaving number is not significant to effect on corn yield, and there is no interaction on the yield. In comparison with conventional treatment, deleaving number is not significant to yield at silking 2-3 cm outside the husks, for eight leaves corn plants treatment, many green leaves can be obtained which the content of crude protein, the digestibility and metabolizable energy were higher than that of dry corn leaves after harvest and Leymus chinensis. The yield was serious decrease to deleave at invisible ear at flowering stage. The yields were different between three treatments when deleaving after ear appearance but no silk was visible outside the husks.(6) There are many sandy, saline-alkaline and infertile crop fields in farming-pastoral zone of Songnen plain, where sunflower could grow well. The traditional tillage system for sunflower in this region is sowing at the beginning of June with 65cm row space and 150-180cm interplant space. We conducted experiments to determine the effects of adjusted row space, interplant space, sowing position and sowing date on sunflower production. The results showed crops with narrow interplant space had high production, and highest production occurred in 60cm interplant space treatment, then was 90cm interplant space treatment. Crops in 98 and 130cm row space treatments had high production, then was 43cm row space treatment which also higher than traditional row distance. The production of corps in furrow sown tillage was higher than those growing in ridge sown tillage. The production of early sowing sunflowers was higher than those late sowing ones. The most late sowing date is 15th June in this region. So the optimal interplant space is 90cm, the optimal row space is 98cm, the optimal sowing position is in furrow, the optimal sowing date is 14th-25 th May.