Effects Of Soil Tillage Systems And Nitrogen Applied Amount On Soil Physical And Chemical Characters, Yield And Quality Of Wheat And Maize

The field experiment was carried out in Zhongcun villages, Longkou City, Shandong Province China, in order to study the effects of nitrogen applied amount, straw returning and four soil tillage systems (including the conventional tillage (C), rotary tillage (R), serrated disk harrow tillage (H), zero-tillage (Z)) on soil physical and chemical characters, crop yield and kernel quality from 2002 to 2005. In this experiment two wheat cultivars Yangnong15, Jimai20 and maize cultivars Zhengdan958 were used. Meanwhile, 15N isotope tracing was adopted. soil fertilizer & water leakage test were the aided experiment, and physiological & biochemical was also studied. The results were as follows:1 Effects of straw returning and nitrogen applied amount on soil physical and chemical characters, yield and quality of wheat and maize1.1 Effects of straw returning on soil physical and chemical characters, yield and quality of wheat and maizeCompared with no straw returning treatment, straw returning treatment improved soil total nitrogen content, alkali-hydrolysable nitrogen content, available potassium content, available phosphorus and organic matter content in 0-40cm soil layer, also it could keep more nitrate in 0-60cm soil layer, reduce its leaching.In high-yield farmland (organic matter content, 1.712%; alkali-hydrolysable nitrogen content, 88.73mg·kg-1; available phosphorus content , 43.27 mg·kg -1; available potassium content, 88.33 mg·kg–1;in 0~20cm soil layer), short-term (2 years) straw returning had no significant effect on crop yield, but it could increase wheat protein content and dough stability time.1.2 Suitable nitrogen applied amount under straw returning conditionIn wheat season, nitrogen applied amount of 240 kg·hm-2 (N2) and 168 kg·hm-2 had no notable effect on wheat yield and maize yield. Meanwhile in the first year N1 and N2 had no significant impact on kernel quality. In the second year, wheat kernel wet gluten content and starch content under N1 treatment were significantly higher than that of N2 treatment, but maize kernel starch content under N2 treatment was noticeably higher than that of N1 treatment, and N2 treatment also changed the ratio of amylase content to amylopectin of maize. So in this experiment, the result showed that under straw returning conditions, 168 kg·hm-2 of nitrogen applied was more suitable.2 Effects of tillage systems on soil physical and chemical characters2.1 Effects of tillage systems on structure of tilthThere was no significant difference in soil bulk density and porosity among R, H and C treatments in 0~10cm soil layer. But in 10~20cm layer, soil bulk density of R and H treatment were noticeably higher than that of C treatment. Soil bulk density of Z treatment was gradually increased in three years, which was significantly higher than that of C treatment in 0~20cm soil layer.2.2 Effects of tillage systems on soil moisture contentThere was significantly positive correlation between soil pondage and rainfall of the same period in R, H and Z treatments, and the correlation coefficient was higher than C, especially the H treatment, its correlation coefficient was 0.70**, which reached a highly significant level, and its soil water retention was better than C. In 0~60cm soil layer, R, H and Z treatments could conserve more water than C and reduce water infiltration and evaporation, especially the H treatment. In different growth stage, the soil pondage of R, H and Z treatments was larger than C, especially in anthesis stage, which indicated that R, H and Z could inhibit the useless evaporation of soil water before anthesis and promote grain filling. Different tillage systems had different Effects on soil pondage. In this experiment, there was no significant difference between R and H treatment. The soil pondage of Z treatment was less than that of R and H, which indicated that Z treatment was disadvantageous to soil water infiltration under irrigation conditions because Z was covered by straw and had high density.The results also showed that soil tillage could affect soil water leakage. Irrigation water leakage volume in 50cm soil layer showed that C>R>H>Z. And the leakage was in the direct ratio to the depth of plowing, which showed the depth of plowing had noticeable Effects on irrigation water leakage.2.3 Effects of tillage systems on nutrient status in 0-40cm soil layerWith the extend of location experiment time, alkali-hydrolysable nitrogen content, available P and available K content of R and H treatments were gradually higher than those of C, total nitrogen content and available P of Z treatment was lower than that of C in 0-20cm soil layer. That was because of topdressing nitrogen fertilizer in Z treatment. But in 20~40cm soil layer, total nitrogen content, alkali-hydrolysable nitrogen content, available P and available K content of C treatment were the highest among all treatments.2.4 Effects of tillage systems on soil organic matter properties and cation exchange capacity (CEC)After three years, the compound degree of soil organo-mineral and the organic carbon in heavy fraction of R, H, Z treatments were higher than those of C treatment in 0-20cm soil layer. Meanwhile, R, H, and Z treatments significantly improved the soil fertility. CEC of H is the highest in 0~20cm soil layer, which indicated that H had the best effects on supplying fertility. But in 20-40cm layer, the results were reversed. So the C treatment had better soil fertility.2.5 Effects of tillage systems on activity of urease and sucraseThe activity of urease and sucrose of Z, H and R were significant higher than C in 0-10cm soil layer, and Z was the highest. But in 10-20cm soil layer, the result showed the reverse trend. The activity of enzymes under R, H and Z treatments had great difference in different layer, but the difference of C was little. That showed C treatment was conducive to maintain the uniformity of soil fertility in 0-20cm soil layer, but Z was unfavorable to crop growth.2.6 Effects of tillage systems on straw decomposition and soil respirationAfter a crop year, straw decomposition of C was remarkably lower than that of R, H and Z treatments, but there was no difference among three treatments. In wheat season, there was no significant difference of soil respiration rate among R, H and C treatments, but the soil respiration rate of Z was lower than that of C. In maize season, the soil respiration rate of C was higher than that of R, H, Z at maize pre-tasselling stage, but at maize maturity stage, the soil respiration rate of C was the lowest.2.7 Effects of tillage systems and nitrogen applied amount on nitrate content in soil2.7.1 Effects of tillage systems and nitrogen amount on content of nitrate in soilThe nitrate movement of H and R was significantly lower than C treatment. The results also showed soil nitrate content of R and H treatments was higher than that of C treatment in conglomeration zone of the root system (0-60cm), while under 60cm soil layer, C was higher than other treatments. Soil nitrate content of Z treatment was the lowest among all treatments.Soil tillage systems had effect on nitrate leaching. After applying fertilizer, soil nitrate content of water leakage under N1 treatment, C was the highest, R was the next, and Z was the last. Apparent nitrogen leaching rate of C was the highest, while that of Z was the lowest. Soil nitrate content of Z was lower than other treatments, and the loss of fertilizer nitrogen volatilization was more than other treatments.2.7.2 Effects of fertilizer application on soil nitrate contentIn wheat season, the nitrate accumulation of N2 was significantly higher than that of N1 in 0-60cm layer (root zone), in 60-100cm layer (danger zone in which leaching always easily occurred) and in 100-200cm layer(the zone leaching easily occurred). Nitrate accumulation of N2 treatment was notably higher than that of N1 treatment, which was the major reason why the nitrate accumulation of N2 was higher than N1. But the nitrate couldn't be used by crop and was easy to leaching. The residual soil nitrate content in wheat season had significant influence on soil nitrate accumulation of maize field, especially the soil nitrate accumulation in 0-60 soil layer. So more soil nitrate accumulation in wheat season, more soil nitrate accumulation in maize season.3 Effects of tillage systems and nitrogen applied amount on wheat growth and development and yield of wheat and maize3.1 Effects of tillage systems and nitrogen applied amount on wheat growth and developmentIn the second year of experiment, there was no significant difference in the wheat flag leaf photosynthesis rate, flag leaf senescence characteristics, photosynthate transferring amount, photosynthate transferring ratio and dry matter accumulation of between R, H and C. In the third year, the photosynthate transfering amount and dry matter accumulation amount of R and H were significantly lower than that of C.Wheat flag leaf under Z treatment had better photosynthesis characteristics and physiological characteristics in the later growth stage. but the flag leaf photosynthate transferring amount and transferring ratio were lower than that of other tillage treatments. This showed that wheat of Z matured later, and inhibited the transfer of photosynthate from nutrient organs to kernels, whose dry matter accumulation was significantly lower than other tillage systems.In the second year, there was no significant effect on the photosynthesis characteristics, senescence characteristics and photosynthate transfer of flag leaf between N1 and N2 treatment. While in the third year the photosynthate transfering amount and transferring ratio of flag leaf under N2 level was higher thant that of N1.3.2 Effects of tillage systems and nitrogen applied amount on yield of wheat and maizeThere was no significant difference of yield among three treatments (R, H and C) after two years experiment, but in the third year, crop yield of C treatment was higher than that of R and H. In this experiment, crop yield of Z was remarkably the lowest. Nitrogen fertilizer had different influence on crop yield in different years. There was no significant effect on crop yield under N1 and N2 level in the first and second year, but in the third year, crop yield of N1 was lower than that of N2. Meanwhile, under N2 level, yield of C treatment was higher than that of H and Z, while under N1 level, crop yield of H was notably higher than that of C treatment, but there was no difference between the yield of R and C treatments.The residual nitrogen fertilizer of wheat season had significant effect on maize yield, and the influence of N2 was greater than N1. The effect became remarkable in the second year and in the third year. The crop yield of R and H treatments was higher than that of C treatment under N2 level, but under N1 level, the crop yield of R and H was lower than that of C treatment, meanwhile, crop yield of Z treatment was lower than that of C treatment.There was significant effect of nitrogen applied amount in wheat season on crop yield, and the yield of N2 treatment was obviously higher than that of N1. The yield of R and H was higher than that of C under N2 level, especially the R treatment. Under N1 level, the yield of R was equal to that of R, while the crop yield of Z was significantly lower than that of C treatment under both N1 and N2 level.4 Effects of tillage systems and nitrogen applied amount on the quality of wheat and maize kernel4.1 Effects of tillage systems on the quality of wheat and maize kernelThere was no significant effect of tillage systems on protein content, wet gluten content and gluten index. While the effect of tillage systems on globulin content in protein fractions was the most obvious and on albumins was less obvious. The sedimentation volume and dough stability time of R and H were higher than that of C. The wheat amylose starch was easier to be affected by tillage systems than amylopectin starch. The wheat kernel starch content of R was higher than that of C, while that of Z and H was lower than that of C. And the wheat kernel starch content of Z was the lowest. There was no significant effect on maize protein content and starch content between C, R and H. The maize starch content of Z varied most among different years. Compared with C, the maize kernel protein content of Z became less as time went.4.2 Effects of nitrogen fertilizer amount on the quality of wheat and maize kernelThere was no significant difference between N1and N2 in wheat kernel protein content in the first year. The wheat kernel protein content of N1 was significantly lower than that of N2 in the second year and third year of Z and in the third year of H. Among protein components, globuln content was affected most significantly, while albumins content was affected less. The sedimentation volume of N2 was higher than that of N1. There was no significant difference between N1 and N2 in wet gluten content, gluten index and farimograph index, which showed that N1and N2 had no significant effects on wheat kernel protein quality. The grain amylose and amylopectin content of N1 and N2 of wheat kernel were different. And the total starch content of wheat kernel of N1 was higher that of N2. There was no significant aftereffect on maize kernel starch and protein content of N-fertilizer in wheat season. This showed that compared with N2, N1 had no significant effect on crop quality.5 Effects of long-term tillage and nitrogen fertilizer on crop nitrogen absorption and utilizationThe results of 15N in 2005 showed that the N-fertilizer utilized efficiency of H was the highest, while that of Z was the lowest. But Z increased absorption of nitrogen from soil significantly. H increased N-fertilizer apparent use efficiency and N-productive efficiency significantly of wheat. The N-physiological use efficiency, N-productive efficiency and N-fertilizer apparent use efficiency of wheat of R, H and Z in N1 level were significantly higher than that of N2 level. While the N-physiological use efficiency, N-productive efficiency and N-fertilizer apparent use efficiency of C of wheat in N2 level were significantly higher than that of N1 level. This showed that R, H and Z could use N fertilizer more efficiently than C in wheat season, among which H was the best.There were some significant effects of nitrogen fertilizer in wheat season on the N-fertilizer utilized efficiency in maize season. The N-fertilizer utilized efficiency in maize season of R and H was higher than that of N and C. Considering the N-fertilizer utilized efficiency in a whole year, H was better than other three tillage systems, while C was the worst. The N-fertilizer utilized efficiency in a whole year of N2 was higher than that of N1 in C and R, and N1 was higher than that of N2 in H and Z.6 Tillage systems adaptability and suitable amount of nitrogenPreliminary conclusion could got that R and H were suitable for short time (1~2 years) in high-yield and irrigation conditions, while Z was not suitable. Nitrogen applied amount of 168kg·hm-2 was enough to maintain a higher yield and better kernel wheat quality.