Studies On Water-holding Capacity And Root Spatial Distribution Of Corn Belt In Songliao Plain

In recent years, large areas of Corn Belt soil in Songliao Plain are under unreasonable farming and reclamation. With the growing cultivation years of corn, the soil fertility degradation is getting worse, especially, water-holding capacity of the soil declines year by year, and easy to get drought, waterlogged and dehydrated causes a serious impact on growth and distribution of maize roots, which all lead to the situation of stagnating and even declining in corn production for many years. Therefore, it is essential to study the water-holding capacity and root spatial distribution of Corn Belt in Songliao Plain. This paper, through comparative analysis of water-holding characteristics and physicochemical properties of "flat type" and "wave type" profile conformation soil formed under current farming system, preliminarily discusses the water-holding properties of Corn Belt soil in Songliao Plain and its influencing factors. It clearly illustrates the reasons for water-holding capacity of the soil declines. In addition, it explores the causes that lead to different of the maize roots based on comparison of distribution state under different profile configurations. The above study was designed to provide a theoretical basis to improve water-holding capacity and root spatial distribution of Corn Belt soil in Songliao Plain.The following conclusions can be drawn from the above research:1. Use pressure membrane instrument to measure the gravimetric moisture content of soils in different profile, and fit out the soil water characteristic curve. On this basis, it comparatively analyzes the water-holding capacity of different profiles of soil, thus clearly states that the difference of water-holding capacity in different profile configuration of Coin Belt soil in Songliao Plain is mainly concentrated in the plow layer of soil, where "flat type" profile soil has much better water-holding capacity than the "wave type" one, but without much obvious changes in plow pan.2. The findings of the relationship between the basic physical and chemical properties of soil and its water-holding capacity show that, organic matter, aggregate, bulk density and porosity have some influence on water-holding capacity of the soil. Among them, organic matter and aggregate have a linear relationship with soil water-holding capacity, and in a very significant positive correlation; soil bulk density has a certain degree of negative correlation with soil water-holding capacity, the greater the soil bulk density, the weaker the water-holding capacity; total porosity was positively correlated with water-holding capacity, in which, organic matter has the highest correlation coefficient with soil water-holding capacity, that is0.9407**, and has a coefficient of0.8420**with water stable aggregates. This demonstrates that declination of organic matter in Coin Belt soil of Songliao Plain destructed the structure of soil aggregates, which might be the main reason of water-holding capacity decreased, and easy to get drought, waterlogged and dehydrated. The existing unreasonable farming system has stronger compaction effect on soil, causing the soil amount of plough layer decrease, and increase soil bulk density, which then leads poor soil permeability. This is another reason of soil water-holding capacity declines.3. Use root washing measurement and analysis software WinRHIZO to calculate and analyze root length, root weight and root surface area of maize roots in different profiles at different growth stages. It found from the result that the variation trend of basic dynamic indicators like the maize root is basically the same, showing a single peak curve. It reaches the peak after15days of the silking stage, and then gradually decreases with the arrival of maturity period. Root length, root weight and root surface area of maize roots basically show a decreasing trend with soil depth increasing, of which about80%of roots are mainly concentrated in the0-40cm soil layer.4. Differences of root weight, root length and root surface area of "flat type" and "wave type" profile soil in the same growth period mainly exists in0-60cm soil layer, when the "flat type" profile is higher than the "wave type" profile. This difference decreases with soil depth increasing, with the most significant difference at surface.5. Nutrient index of available phosphorus, potassium and nitrogen have less obvious difference in0-100cm soil layer in both "flat type" and "wave type" profile, with difference ranging from0.28-3.lmg kg-1. However, there are some differences in organic matter and soil bulk density in the middle and upper layer (0-60cm soil layer), organic matter in the "flat type" profile is higher than the "wave type" profile soil, but lower soil bulk density in it is lower than the latter. Differences are not obvious in deep soil of these two profiles.6. Through correlation analysis of the basic indicators of soil root based on the organic matter and bulk density of the "flat type" and "wave type" profile, it found that the organic matter content showed a highly significant positive correlation with root weight, root length and root surface area; its correlation coefficient with root length is up to0.9836**(p<0.01) in the maturity period. While the bulk density has a significant negative correlation them, whose correlation coefficient with root length is up to-0.8705**(p<0.01) in the maturity period. This shows that organic matter content and soil bulk density are important factors that affect Corn Belt.