Effect Of Continuous Cropping On Photo-Physiological Parameters And Nutrient Absorption And Yield Of Maize Released In Different Decades

In this study,10 representative maize cultivars bred from Dandong Academy of Agricultural Sciences and Shenyang Academy of Agricultural Sciences from the 1980 s to 2015 were used as test materials.The photo-physiological parameters and nutrient contents of maize cultivars grown in different ages were determined under continuous cropping and rotation conditions.Dry matter accumulation and distribution,plant agronomic traits and yield-related traits.The effects ofcontinuous cropping and rotation on photosynthetic physiology,nutrient uptake,dry matter accumulation and yield formation of maize cultivars from different ages were discussed.The nutrient uptake and yield formation of maize under different cultivation patterns were analyzed with the different cultivars of maize released in different ages.The main results are as follows:1.Effects of continuous cropping on the photosynthetic characteristics of cultivars released in different decades.At different growth stages,the leaf area index,leaf greenness and net photosynthetic rate of maize cultivars grown in different conditions in continuous cropping conditions were lower than those in rotation conditions.In the dough stage,compared with the rotation,the leaf area index,leaf greenness and net photosynthetic rate of continuous cropping maize cultivars decreased by 4.38%,4.38%,and 5.12%,respectively;continuous cropping two-year leaf area index,leaf greenness,net photosynthetic rate was reduced by 9.48%,5.99%,and 8.25%,respectively.It indicated that the photosynthesis interception and photosynthetic capacity of maize were significantly higher than those in continuous cropping conditions in the dough stage.This facilitates higher dry matter accumulation and yield.2.Effects of continuous cropping on nutrient accumulation and distribution of cultivars released in different decadesThe percentages of nitrogen,phosphorus and potassium in the straws,leaves,leaf sheaths,bracts,cobs and kernels of maize cultivars grown in different conditions in continuous cropping conditions were lower than those in rotation conditions.In the dough stage,compared with the rotation,the reduction ratio of nitrogen in each organ of continuous cropping for one year was 6.99%,10.15%,2.13%,3.23%,1.47%,and 8.17%.3.79%,12.10%,3.14%,6.57%,8.98%,3.15%;the reduction ratio of potassium in each organ was 4.39%,7.17%,7.65%,7.93%,5.12%,9.69%;The reduction ratio of nitrogen in each organ was 7.44%,12.82%,10.79%,4.10%,2.77%,10.91%,respectively.The reduction ratio of phosphorus in each organ was 8.14%,14.91%,5.06%,7.68%,9.85%,14.17%;the reduction ratio of potassium in each organ was 9.61%,10.03%,11.79%,9.35%,12.07%,14.48%.Compared to the rotation,continuous cropping of corn requires more nitrogen and phosphorus nutrients in the same yield.With the advancement of breeding process,the nitrogen,phosphorus and potassium nutrients required for each 100 g kernel production showed a downward trend,indicating that the nutrient use efficiency of corn increased with the progress of breeding.4.Effects of continuous cropping on dry matter accumulation and distribution of cultivars released in different decadesUnder continuous cropping conditions,the dry matter accumulation and biomass per plant of straws,leaves,leaf sheaths,bractss,cobs and kernels at different growth stages of maize varieties grown in different ages were lower than those under rotation.At the maturity stage,compared with the rotation,the reduction rate of dry matter accumulation in straws,leaves,leaf sheaths,bracts,cobs and kernels of successive crops was 9.96%,8.99%,7.65%,10.22%,and 6.26%.6.86%,10.07%;the reduction rate of dry matter accumulation in straws,leaves,leaf sheaths,bracts,cobs and kernels of two-year maize varieties was 11.64%,12.55%,13.74%,8.85%,12.23%,12.08 %;the reduction rate of single plant biomass per year for continuous cropping maize was 8.04%;the reduction rate of single plant biomass for continuous cropping two-year maize varieties was 8.58%.With the advancement of breeding process,the dry weight of straws,dry weight of leaves,dry weight of leaf sheaths,dry weight of bracts,dry weight of cobs,dry weight of kernels and biomass per plant decreased.It indicated that with the advancement of breeding process,the effect of continuous cropping on the biomass per plant and the accumulation of dry matter in straws,leaves,leaf sheaths,bracts,cobs and kernels became smaller.5.Effects of continuous cropping on agronomic traits and yield of cultivars released in different decadesCompared with the rotation,continuous cropping reduced kernel lines per ear,kernels per line,kernels per ear,100-kernel weight,and ears in different ages.The difference in 100-kernel weight was the most significant.The kernel yield of the currently grown cultivars was significantly higher than that in the early and medium stage.With the progress of breeding,the reduction rate of 100-kerel weight decreased.With the advancement of the breeding process,it showed that the impact of continuous cropping on the 100-kernel weight becomes smaller.The average yield of maize for one year in a row was lower than that of the average yield of maize for two years.With the advancement of the breeding process,it showed that current maize hybrids had a stronger tolerance to continuous cropping as compared with the old hybirids.