Physiological And Ecological Mechanism Of Stable And High Yield Of Broadcasted Rice In Paddy Field With High Standing-stubbles Under No-tillage Condition

In order to understand Physiological and ecological mechanism of stable and high yield of broadcasted rice in the field with high standing-stubbles under no-tillage condition, a study was executed in Pixian county of Sichuan province in 2005 and 2006, and it included four experiments: tillage methods + straw treatment; nitrogenous fertilizer applying; planting method + varieties; planting method + potassium fertilizer (kalium, K) amount applied. It researched effects of Broadcasted Seedlings in Paddy Field with High Standing-stubbles under No-tillage Condition (BHSNT) to Physical and chemical characteristics of soil, microflora, root distribution, accumulation of dry matter, use of nitrogenous and potassium fertilizer, leaf consenescence at middle and late period, lodging characteristics, yield and its factors. The main results are as follows:1. Under the different returning straw to soil and tillage methods, in the upper layer of soil, the organic matter content for 'no-tillage + returning straw' treatment is 5.33, 2.79 and 5.37 g/kg higher than that for 'no-tillage', 'tillage + returning straw' and 'tillage' treatment, respectively; then its contents of total and available N, P and K are the highest too, those for 'no-tillage' treatment and 'tillage + returning straw' treatment followed, and those for 'tillage' treatment are the lowest. In the lower layer of soil, the fertile indicators for 'tillage + returning straw' treatment are higher than those for other treatments. Soil bulk density under water and bulk density for 'no-tillage' are higher than that for 'conventional tillage'; and soil porosity is lower than that for 'conventional tillage'.The treatment 'returning straw to soil' increases the population of soil microbes. The populations of bacteria, fungi and actinomycetes for 'no-tillage + returning straw' treatment are the highest in the upper layer of soil. Its fiber decomposition intensity is 26.44%, 79.01% and 98.15% higher than that for 'tillage + returning straw', 'no-tillage' and 'tillage' treatment at maturity period respectively. In the lower layer of soil, however, the populations of bacteria, fungi and actinomycetes for 'tillage + returning straw' treatment are higher than those for other treatments. The 'no-tillage + returning straw' treatment enriched soil fertility and microbes on surface layer of soil. The bacteria, actinomycetes and soil fiber decomposition intensity are significant positively correlated with soil fertility.2. In different planting methods, weight of roots per stem shows that BHSNT is heavier than no-tillage & broadcasting seedlings, and approximately equal to Conventional tillage & broadcasting seedlings (CTB), and conventional tillage & transplanting (CTT); most distribution proportion of roots within 0-5 cm under soil surface vertically is no-tillage & broadcasting seedlings, BHSNT and CTB followed, and CTT least. Proportion of root distribution within 5-10 cm under soil surface for different planting methods is just opposite to that of roots within 0-5 cm under soil. Proportion of roots distribution of CTT and CTB within 10-20 cm under soil is more than that of no-tillage & broadcasting seedlings and BHSNT; proportion of roots distribution of no-tillage & broadcasting seedling within r= 5-10 cm under soil surface horizontally is more, CTB and BHSNT are at close level; CTT is less. Proportion of root distribution within 5-10 cm under soil surface for different planting methods is just opposite to that of roots within r = 5 cm under soil.3. Compared with CTT, Accumulative amount of potassium (kalium, K) of BHSNT is higher at tillering stage and elongating stage, lower at other stage, however. Total accumulative amount of potassium with method CTT is more than that with method of no-tillage & broadcasting seedlings, more than that of CTB, and more than that of BHSNT. However, varying trends of rice production efficiency with potassium, harvest index with potassium are opposite to that of dry matter production efficiency with potassium at maturity stage: that of BHSNT is more than that of CTB, more than that of no-tillage & broadcasting seedlings and more than that of CTT.Nitrogen is the indispensable nutrient to rice production. Increasing nitrogen fertilizing amount improves N-content of leaf and stem, and increases the amount of N leaving in straw at maturing stage (MS). With the increasing of nitrogen fertilizing amount, total N accumulated (TNA) at every stage is improved notably, but N production efficiency and N harvest index (NHI) are reduced. At tillering stage (TS) and jointing stage (JS), TNA is higher when fertilizing N as 10:0:0 and 7:3:0, but at heading stage (HS) and MS, it is higher when applying N as 7:0:3 and 4:3:3. N fertilizer availability is increasing along with increasing of N fertilizer applied. Under low N level, it is higher when applying N as 10:0:0 and 7:3:0. With high N level, it would be highest when applying N as 4:3:3.4. BHSNT and BLSNT increase the SPAD value and SPC of leaf. Compared to CTB and CTT, the SPAD value of BHSNT is increased by 3.43%, 3.54% respectively, the SPC is increased by 13.57%, 15.26% respectively, the SPAD value of BLSNT is increased by 2.22%, 2.32% respectively, and the SPC is increased by 6.67%, 8.26% respectively, and declined slowly. BHSNT and BLSNT decreases the POD activities of leaf days after heading, increased the activities of SOD and CAT in the late growth duration. Compared to CTB and CTT, the activities of POD are decreased by 21.04%,15.78% respectively under BHSNT, the activities of SOD are increased by 16.81%, 8.82% respectively, the activities of CAT are increased by 43.43%, 27.06% respectively; under BLSNT, the activities of POD are decreased by 13.00%, 9.95% respectively, the activities of SOD are increased by 13.41%, 5.65% respectively, the activities of CAT are increased by 20.00%, 6.31% respectively.Three enzymes synergies reduce the rate of O₂^- production speed and MDA content. Under BHSNT, the rate of O₂^- production speed is decreased by 29.87%, 18.75% respectively, MDA content is decreased by 9.84%, 7.08% respectively. Under BLSNT, the rate of O₂^- production speed is decreased by 25.95%, 15.16% respectively. MDA content is decreased by 9.91%, 7.14% respectively, thus eased the speed of chlorophyll degradation and membrane peroxide, which effectively eases the leaf senescence.5. Among factors in root lodging coefficient (RLC), the correlative coefficient between dry weight of roots per stem (W) and RLC is the most, plant height (H) is least; the correlative coefficient between mechanical intensity of stem (M) and fresh weight per stem (G) is different in different period. Moreover, the correlative coefficients between W and RV, M and wall thickness of stem, M and DS, M and DSS, PBS and KC, G and FSW, G and FLW reach significant levels. The root lodging coefficient (RLC) of CTT, BHSNT, BLSNT and CTB are 2.72-5.82, 2.54-5.68, 2.32-5.39 and 2.42-5.15, respectively, which indicates the root lodging resistance of CTT is the least, the root lodging resistance of BHSNT is less than that of CTB and BLSNT, and the root lodging resistances of CTB and BLSNT are strong at close level.Most distribution proportion of roots within 0-5 cm under soil surface vertically is no-tillage & broadcasting seedlings, BHSNT and CTB followed, and CTT least.With different kalium (K) amount fertilized, the RLC of no-tillage and broadcasting seedlings is decreased along with K increased, which indicates that the root lodging resistance of plants is increased along with K increased. It can boost the development of BLSNT root (including increasing W and RV and boosting root to distribute in the soil in radii of 5-10 cm) to enhance fixing force of rice plant. And it can reduce FSW and FLW to relieve lodging power and bending moment, and increases DS, DSS, PBS and KC to improve the quality of haulm by using K.6. Two experiments of planting method & varieties and planting method & K amount fertilized indicate: difference between yield of BHSNT and that of other planting methods is not notable. As a technology of labor-saving, it features stable and high yield. As far as analysis from yield composition is concerned, effective seed-heads of BHSNT is higher than that of all other planting methods. According to regression analyzing, parabola relationship between yield and TNA at MS is found, from the equation it can be calculated that the yield is highest when N-uptaking amount is 150.5 kg/ha. Yield varies from different N application. When increasing fertilization of nitrogen amount, yield increases, and it is highest when amount of N fertilized is 150 kg/ha, more fertilization will reduce the yield, however. Number of seed-heads and seed-heads grain are increased along with increased N amount fertilized. Number of seed-heads grain is most when N fertilization is 150 kg/ha. Ripening rate is decreased along with increased N amount. Yield with N fertilizer proportion 4:3:3 (base: tillering: seed-heads) is highest.