Effects Of Tillage And Cultivation On Cropland Eco-environment And Yearly Productivity In A Wheat-rice Double Cropping System

No-tillage plus inter-planting and straw return is a recently-developed farming practicein China, which produces profound effects on cropland eco-environment and the growthof rice and wheat. In order to provide a solid technological and theoretical support forlight-duty, high yield, high quality and efficient production in rice and wheat, and toprovide a scientific guidance for carrying out no-tillage, reasonable rotation tillage andstraw returning more efficiently, different tillage and cultivation methods were adopted tostudy their effects on cropland eco-environment, nutrition supply in soil and absorptionin rice and wheat, rice and wheat growth, yield and grain quality, and yearly productivity.Four different tillage and cultivation treatments lasting 3 consecutive years (no-tillageplus straw mulching, NTS; no-tillage plus high stubble remaining, NTH; conventionaltillage plus straw returning, CTS; and conventional tillage plus no straw returning, CT)were carried out both in net house and in the open field. The main results were asfollows.1. Under NTS, the height of rice stubble remained on the field significantly affectedthe light transmission rate in sunny days,with an optimal height of 20-30 cm. NTS andCTS decreased soil temperature at noon in sunny and warm days, but slightly increased itin the morning and evening, which led to a less diurnal difference. The average diurnaltemperature under NTS and CTS was lower in sunny day, but higher in cloudy day.2. Under NTS, soil water content was higher under drought condition, and soilpermeability after irrigation was better, which was propitious to the growth of wheat..NTS was suitable to prevent water evaporation, decrease surface runoff and better waterpermeability in soil. In concrete ponds in net house where no water leaking, PH readingwas decreased and COD was increased under NTS,NTH and CTS. PH reading within30d under NTS was at most 1 lower than under CT. COD under CTS, NTH and NTS was3, 8-12 and 11-17 times as much as under CT. While in the open field, the variations ofPH reading and COD were not so big, producing insignificant effects of rice growth. 3. Under NTS and NTH, both the soil bulk and penetration resistance of topsoil increased,but no apparent adverse effects of them were observed on wheat and rice growth. Strawreturning significantly improved soil structure and increased soil nutrients content. After3 years straw returning, soil organic matter, total N, available P and K in CTS treatmentincreased 4.7%-13.0%, 0%-10.6%, 0.25%-10.6% and 8.4%-15.5%, respectively,compared with that in CT. Of which, the increments of available K were the biggest.Straw returning also produced certain buffer and regulating effects on available N in soil.In CTS treatment, available N content in soil decreased to some degree at the earlierstage of treatment, but increased significantly at the later stage. Straw returning providedadequate energy and carbon sources for the aggregation of soil microorganisms, whichwas helpful to the validation of available P and K, especially at the later stage. Strawreturning increased soil microbial biomass nitrogen content. When wheat was harvested,soil microbial biomass N was highest in CTS, but when rice was harvested, that washighest in NTS. Both were twice as much as under CT.4. Rice straw embedded into soil layer in wheat field decomposed faster than mulchedon the surface. And the highest decomposition rate was detected at the embedding depthof 14cm. This indicated that the closer contact between soil and straw was helpful tostraw decomposition. Owing to the water layer, higher moisture and temperature in ricefield, the wheat straw embedded in rice field decomposed faster than the rice strawembedded wheat field. Through the decomposition of one cropping season, the residualrates of the rice straw in wheat field and that of embedded the rice straw in wheat fieldwere 60% and 40%, respectively. While the residual rates of wheat straw in rice field andthe residual rates of embedded wheat straw in rice field were 25% and 20%, respectively.Compared with CTS, NTS fixed more nitrogen, produced less nitrogen for wheat andrice growth, but it increased the utility rate of nitrogen. Through decomposition, C/Nratio decreased due to the loss of total C. The C/N ratio of rice straw in surface layer ofwheat field remained high, while that of wheat straw was the lowest in surface layer andwas the highest in mid-layer of rice field. The C/N ratios of crop straws at earlydecomposition stage were not significantly affected by embedding depth but were closerelated to their initial nitrogen contents. The C/N ratio of rice and wheat straw after onecropping season was around 30 and 15, respectively, higher than that in humus, whichindicated that the decomposition process was not fully accomplished.5. Straw returning inhibited the germination and emergence rate in wheat, which led toa smaller population of basic seedlings. Straw returning also made the damage offreezing to wheat seedlings more serious. Dry matter accumulations in wheat in NTS andNTH were lower than that in CT, i.e. 15% less in average was detected at the ripeningstage. But no significant differences were observed between NTS and NTH, CTS and CT.Due to slightly lower content of N and P in wheat grains, the total accumulations of N, P and K under NTS and NTH were 20% lower in average than that under CTS and CT.Under the same planting date and seeding amount, the number of spikes under NTS andNTH was smaller, but the kilo-grain weight was higher. The grain yield was slightly butnot significantly lower under NTS in the first year. With more lodged stubble and weedsin the second and third year of no-tillage, which affected wheat germination and seedlingemergence, leading to a significant decrease in wheat yield. On average,the grain yield inNTS treatment was 7.27% lower than that in CT. In order to increase grain yield, seedingmethod must be optimized, or rotation tillage must be adopted. Compared with CT,wheat yield of CTS was higher or lower in different years. But the average yield in 3years was 1% lower than that of CT. The wheat test weight under NTS was low, but flourrate was high, with the best commercial quality. When the soil was infertile, the crudeprotein content and wet gluten content tended to decrease. While NTS and CTS increasedthe crude protein content and wet gluten content, which was beneficial to theoptimization of wheat commercial quality.6. Compared with CT, NTS and NTH reduced the height of rice plants, leaf area perplant and the biomass of rice plants, but the treatments accumulated the biomass morequickly at the later stage. As for dry matter accumulation in rice, CTS was lower than CT,especially at the elongation stage, and NTS was also lower than NTH. With rice growth,the content of N, P and K in rice plants decreased gradually. At the ripening stage, thedifference of the content of N in rice plants between NTS and CTS was insignificant. Butthe content of N in both rice plants and rice grains under NTS and CTS was significantlyhigher than CT. At the ripening stage, the content of P and K under NTS and NTH washigher than CT. The accumulated content of N, P and K under NTS and CTS was higherthan NTH and CT, but the differences between NTS and CTS, NTH and CT were bothinsignificant. If the problems of seedlings erectness and weeding could be solved, therice yield under NTS and NTH could be as high as, or even slightly higher than thatunder CT. In all treatments, the rice yield under CTS was the highest, 3% higher than CTon average. The rice yield under NTS was also high, 0.8-3.1% higher than CT in average.When the difference between the number of spikes per unit area was not significant, thenumber of kernel per spike under NTS and NTH was smaller, but the kilo-grain-weightwas higher, and the rice yield was also higher than CT. The main reason was that rootactivity under NTS and NTH was higher, and more dry matter was accumulated at thelater stage, and the resistance to diseases and insects was also stronger. Rice under NTSand NTH enhanced the processing quality and eternal quality significantly, thepercentage of brown, milled and head rice increased while chalky rice and chalkinessdecreased. CTS also increased percentage of head rice and slightly reduced chalky riceand chalkiness. The cooking quality of NTS and NTH was improved due to the increaseof protein, decline of amylose content and the increase of gel consistency of rice starch, while CTS increased both protein and amylose contents and decreased gel consistency,which contributed to the decline in quality of cooked rice.7. The comprehensive evaluation of soil fertility indicated that nutrient fertility index(NFI), was the highest under NTS, and was the lowest under CT. But integrated fertilityindex (IFI) was the highest under CTS, and was the lowest under NTH, as for IFI wasmainly affected by the bulk density. IFI could be used as the index of soil actualsustainable productivity, while NFI could be used to indicate soil potential sustainableproductivity. CTS could maintain the highest soil sustainable productivity, while NTShad the highest soil potential sustainable productivity.Wheat yield under NTS and NTH was relatively low, but rice yield increased to someextent. But the total yield of rice and wheat under NTS and NTH was higher than that ofCTS and CT, considering wheat yield in rice seedling field. Technically and economically,NTS and NTH could increase the total yearly productivity and increase the total incomeas long as NTS and NTH technology was extended to individual farmers. Highest yearlyproductivity and yearly economic productivity were observed under NTS. NTH took the2nd place. CTS was in the 3rd place, while CT was the lowest. Compared with CT, CTSachieved a higher yield and productivity. Considering the effects of CTS on soil fertilityand the decreased fertilizer usage, the efficiency was obsolutely obvious.The targets of modern agriculture are high yield, high quality and sustainabledevelopment. In this paper, comprehensive appraisal system was proposed to give a fairevaluation to the yearly productivity of rice and wheat under different rice and wheatdouble cropping systems. In the system, the yield and output were selected as the indicesto evaluate yielding ability, the total cost and the total pure income were selected as theindices to evaluate efficiency, NFI and IFI were selected as the indices to evaluate thecapability of sustainable development. Based on the importance of yield, efficiency andsustainable development, the weight of them was 35%, 35% and 30%, respectively. Inyielding ability, 20% was given to yield, and 15% was given to the total output. Inefficiency, 15% was given to the total cost, and 20% was given to the total income. Insustainable development, 10% was given to NFI, and 20% was given to IFI. According tothis evaluation system, 4 types of tillage and cultivation methods were evaluated. Theappraisal results indicated that NTS got the highest score, and the yearly productivity wasthe highest. NTH took the 2nd place. CTS took the 3rd place. CT was the last.