| No-tillage and straw returning is a recently-developed farming practice in China, which produces profound effects on cropland eco-environment and the growth of rice and wheat. In order to provide technological and theoretical support for light-duty, high yield, high quality and efficient production in rice and wheat rotation system, and to provide scientific guidance for carrying out no-tillage, reasonable rotation tillage more efficiently, different tillage and cultivation methods were adopted to study its impact on cropland eco-environment, nutrition supply of soil and absorption of plants, the growth regulation, yield and grain quality of rice and wheat. The impact of no-tillage and straw-returning on cropland eco-environment and yearly productivity were studied through different tillage and cultivation located treatments. The main results were as follows.1 Although the topsoil bulk (not exceeded 1.45 g·cm-3) and penetration resistance (not exceeded 350 N·cm-2) of no-tillage treatments increased, they didn't hamper the growth of wheat roots in the next season. Straw-returning brought down the topsoil compaction in no-tillage treatment, while it brought down the below layer of topsoil compaction in tillage treatments. In the first month after wheat sowing, the soil respiration rates descended as the falling of soil temperature, especially in the no-tillage treatments.2 Through four years straw returning, soil organic matter, total N, hydrolysable N, available P and K in CTS(convention tillage and straw returning)increased 1.6%-5.7%,1.6%-10.5%,2.8%-14.9%,4.9%-17.9%,3.5%-5.0% compared with CT(convention tillage)after rice harvest, while the effect of straw retuning was not apparent in no-tillage treatments. The soil organic matter and total N chiefly accumulate in 0-7cm of topsoil in no-tillage treatments. Straw returning had buffering capability on soil available N. The straw provided enough nutrition matter for soil microorganism and accelerated its activity, which improved soil microorganism N, soil available P and K.3 Because of no seedling and the interference of wheat stubble in no-tillage treatment, the height and tiller quantity of rice were lower. Rice grew rapidly in the later stage in treatments with straw returning, which increased the danger of rice lodging. Twenty days after rice heading stage, the N transformation to flag leaf was promoted in treatments with straw retuning, which ameliorated leaf nitrogen, improved rice photosynthetic rate and decreased its detraction. As for dry matter accumulation, it was decreased in treatments with continuous no-tillage and was decreased in the treatments with straw returning in the early stage. But the difference of dry matter accumulation between all the treatments was not apparent in the ripening stage. With rice growth, the content of N, P, K in rice plants decreased gradually, except the content of K in CTS1 and CTS2 treatment in late tillering stage. As for the accumulated content of N, the treatments with no-tillage were higher than the treatments with tillage, the treatments with straw returning were higher than the treatments without. Straw returning was beneficial to the accumulated content of P. The accumulated content of K in no-tillage treatments was lower than that in CT, which might be related with the lower dry matter accumulation. Rice yield was higher in treatments with straw returning, but was lower in continuous no-tillage treatments. Though rice appearance quality had tendency to become worse in NTS, the difference of rice milling and appearance quality was not apparent between all the treatments. Rice nutritional quality was ameliorated in NTS (no-tillage and straw mulching), while it was deteriorated in CTS. In treatments with straw returning, the peak viscosity and breakdown increased, while setback decreased. It showed that straw returning ameliorated rice cooking quality.4 The jointing stage was the separation of wheat growth. Before the stage, topsoil temperature was improved because of straw returning, which promoted the growth of wheat, but the plant of wheat was tenuous. After the stage, the growth of wheat was hampered, and encumber was related with straw quantity. The highist internode length was decreased in straw returning treatments. So straw returning ameliorated wheat plant trait and improved the ability of lodging resistance. The area of wheat upper-three-leaf was lower in no-tillage treatments. The area was higher in treatments with reasonable quantity straw returning, which created a base for a higher yield. As for the dry matter accumulation, the no-tillage treatment was higher before the jointing stage, and the treatments with straw returning were higher in the whole stage. With wheat growth, except the content of P in wheat plants had restorative increase in raising stage, the content of N, P, K decreased gradually. Straw returning was beneficial to the absorption of N, P, K in the later stage, which might be related with the activity of microorganism and the buffering capability of straw. The cultivation didn't have apparent effect on the accumulation of N in plants, but it was improved in treatments with straw returning. The absorption of P and K was decreased in no-tillage treatments in the later stage. Wheat yield was increased in treatments with conventional tillage plus reasonable straw returning. While NTS and CTS increased the protein and wet gluten content, this was beneficial to the processing quality of strong (or middle) gluten wheat. The peak viscosity decreased in no-tillage and straw returning treatments, which was not beneficial to the noodle quality of middle gluten wheat. |
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