| This study was conducted from 2009 to 2014 at State Key Laboratory of Crop Science and Wenkou town(36°11′N, 117°06′E, 158 m a.s.l.), Taian, Shandong Province, China. Two hybrids Zhengdan958 and Tainong 18 were used as experimental materials. Integrated agronomic management experiment and nitrogen test were designed at the same time to investigate effects of integrated agronomic management practices on grain yield and nitrogen efficiency in winter wheat-summer maize rotation system and root growth and development of summer maize. The main research results are as follows:1. Effects of integrated agronomic management on grain yield and yield components in winter wheat-summer maize rotation systemThe winter wheat yield of high yield and high efficiency treatment(T2), high yield treatment(T3) and further high yield and high efficiency treatment(T4) were increased by 27.2%, 52.8% and 40.9% compared to traditional cultivation treatment(T1); summer maize yield of them were increased by 15.9%, 41.1% and 29.2%; the total yield in year of them were increased by 20.3%, 45.7% and 33.7%. The 1000-grain weight and kernels per ear of T2 were increased significantly by raising winter wheat nitrogen application proportion in jointing stage, optimizing nitrogen application rate and date of summer maize and delaying summer maize harvest date and winter wheat sowing date. By increasing planting density, the harvest ear number per hectare of T3 and T4 were increased significantly, which was the main reason for its high yield. Compared with high investment of T3, T4 reduced nitrogen application rate and improved the efficiency of nitrogen significantly, achieved both high yield and high N efficiency synchronized.2. Effects of integrated agronomic management on dry matter accumulation in winter wheat-summer maize rotation systemIntegrated agronomic management had significant effects on the dry matter accumulation of winter wheat-summer maize rotation system. The dry matter accumulation in summer maize of T2, T3 and T4 were increased by 7.2%, 41.5% and 24.6% compared to T1; the dry matter accumulation in winter wheat of them were increased by 5.2%, 27.2% and 14.8%. The dry matter accumulation accumulated from VT to R6 were higher for T4 than for T1, T4 obtained higher dry matter increased grain yield.3. Effects of integrated agronomic management on nitrogen efficiency in winter wheat-summer maize rotation systemThe NRE of T2, T3 and T4 in rotation system were increased by 54.1%, 37.9% and 72.7% compared to T1; the NPFP of them were increased by 75.3%, 2.8% and 70.1%; the NAE were increased by 153.2%, 73.2% and 191.6%. The residual nitrogen recovery efficiency(RENRE) of T2, T3 and T4 in summer maize were increased by 2.8%, 6.3% and 19.6% compared to T1; those in winter wheat were increased by 7.5%, 14.6% and 10.6%. These indicated that optimizing integrated agronomic management could improve the efficiency of nitrogen significantly in rotation system, also could improve the efficiency of residues nitrogen.4. Effects of integrated agronomic management on root growth and development of summer maize4.1 Root dry weightThe individual root biomass of T4 increased 53.1%, 35.6%, 29.8% and 37.5% than T1 at V6, VT, R3 and R6; the population root biomass were increased by 91.3%, 69.5%, 62.3% and 71.9%. Result from NT revealed no significant increase in root dry weight in response to N applied above 184.5 kg ha-1. T4 significantly increased root biomass across 0-30 cm soil profile in the whole growth stage.4.2 Root morphology Root volume and root length density across 0-30 cm soil profile under T4 were significantly increased in the whole growth stage, and those across 30-90 cm soil profile were significantly increased at R3 and R6. Result from NT revealed no significant increase in root volume and root length density in response to N applied above 184.5 kg ha-1.4.3 Root activity Root active absorption area of T4 showed a significant increase in the 0-30 cm soil layer at VT, R3 and R6. Result from NT revealed no significant increase in root active absorption area in response to N applied above 184.5 kg ha-1.4.4 Root distribution Root ratio of T4 increased in 0-60 cm soil layer at VT, and increased in 0-30 cm and 60-90 cm soil layer at R3 and R6. Root ratio of N3 in 0-30 cm soil layer maintain the highest at whole stage.4.5 Root/shoot ratio The root/shoot ratio of different treatments decreased with growth stage. Root/shoot ratio of T3 and T4 increased 23.6% and 14.5% at VT; 2.3% and 16.3% at R6 respectively. Root/shoot ratio of N0 was significantly higher than other nitrogen treatment at V6. Root/shoot ratio of N1, N2 and N3 increased 15.4%, 71.8% and 25.6% than N0, respectively. |
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