| High yield not merely requires soil could provide sufficient nutrients, but also require soil has the coordinating physical environment condition within water, air and heat. Due to long time continuous cropping, rotary tillage, applying fertilizer alone and no or less manure in maize cultivation, soil quality declined seriously which showed as soil hardening, thin topsoil layer, large soil bulk density, poor soil structure, etc. In spite of the relationship of soil physical properties and crop growth were very clearly, however there was less research on soil physical properties that fitting different crop growth in different soil types. This paper firstly studied the characteristics of physical properties of high yield maize farmland, afterwards took brown soil as experimental material, using pot and field pot experiment studied soil bulk density, porosity and topsoil layer thickness which affect maize growth. The research results have important theoretical significance of high and stable yield. It also has reference value of agricultural production practice. The results were as follows:1.90%field’s topsoil, subsoil thickness were between20～25cm and7～10cm when yield is greater than750kg/mu, soil bulk density and hardness were range from1.30～1.33g cm-3and3.1～5.1kg cm-2, respectively. Total porosity and aeration porosity of topsoil were range from50%～52%and10%～15%, respectively. Topsoil waterstable aggregate content was greater than20%, water stability coefficient was greater than25%after maize cropland investigation. When the yield was between450and750kg/mu, almost90%topsoil and subsoil thickness were range from16to19cm and10to16cm, topsoil bulk density and hardness were range from1.33to1.38g cm-3and5.5to7.5kg cm-2. Topsoil total porosity and aeration porosity were range from41%to44%and8%to12%. Waterstable aggregate content was less than18%, water stability coefficient was less than22%.2. Results of different topsoil thickness plot experiment showed that, the overground and underground part of maize increased as the thickness of topsoil increased, and it had no effect on chlorophyll and photosynthetic characteristic. There was no significant difference in plant height and spear thickness which increased10%when topsoil thickness was greater than30cm, and the other maize growth index increased slowly. Plot experiment showed that total root amount decreased when topsoil thickness was less than15cm, and the topsoil root distribution rate increased10%and20%which showed a compensation of root. There was no significant difference of different treatment to total root amount, when topsoil thickness was greater than30cm. To sum up the plot experiment results, it can be concluded that topsoil thickness which fit maize growth was range from20to30cm. It will have the negative effect on maize growth if increased topsoil thickness more than30cm, and the economical efficiency will decrease.3. Results of different soil bulk density plot experiment showed that:1) Soil bulk density increased from sowing to seeding stage, then increased slowly during the whole growth stage and decreased during filling stage when soil bulk density was range from1.1to1.4g cm-3and soil organic matter was13.79g kg-1. The soil bulk density treatments of1.1and1.2g cm-3were stabled at1.26to1.31g cm-3and1.28to1.33g cm-3during the growth stage. While the1.3and1.4g cm-3treatments were stabled at1.34to1.38 g cm-3and1.43to1.45g cm-3. This result illustrate that low soil bulk density could not be stable and increased sharply after tillage in low organic matter soil.2) Soil total porosity affect maize root deeply. Maize root growth index significant higher than low porosity treatment when total porosity was range from49.9%to51.2%. Root growth index decreased as total index decreased, however, it had no significant difference in total porosity when total porosity was less than48%. Different porosity influenced root activity, root activity showed an increasing tendency during filling stage. There was no significant difference when total porosity was greater than49.9%and root activity significant decreased when total porosity was less than48%.3) Chlorophyll content increased during the whole maize growth stage. Significant affect was after the jointing stage of different aeration porosity treatment. There was a negative relationship between photosynthetic rate with soil bulk density and the intercellular CO: concentration, and photosynthetic and stomatal conductance had a positive relationship. Maize photosynthetic efficiency was higher when aeration porosity was range from8.6%to11.0%.4) Soil bulk density had a significant effect on nitrogen, phosphorus and potassium in maize root, stem and leaves (P<0.5). The accumulation of the same element of the same maize physiology part in the same growth stage decreased, except potassium content was decreased first then increased, all the other element content decreased. This result lead to yield in the soil bulk density treatment of1.1and1.2were significant higher than1.3and1.4treatment (p<0.01). There was no significant difference of all indexes in the treatment of1.26to1.33g cm-3, this range of soil bulk density was the suitable scope which fit maize growth.5) When soil organic matter was less than1.5%, it restricted maize growth. Soil total porosity significant increased with9%, aeration porosity increased40%to50%, field moisture capacity increased9%to30%and soil bulk density was decreased5%to12%when soil organic material content was3%to5%. With low soil bulk density (1.2g cm-3) and high soil bulk density (1.4g cm-3), soil organic material should increased to3%and4%,respectively which could meet the standard requirement of physical conditions of maize high yield.4. Took field investigation, field plot experiment and plot as a whole, the physical character of high yield maize cropland need the topsoil thickness range from20to30cm, total porosity and aeration porosity was range from50%to51.2%and10%to11%, respectively. Soil bulk density should be stabled at1.26to1.33g cm-3... |
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