Nitrogen Deep Placement Combined with Straw Mulch Cultivation Enhances Physiological Traits, Grain Yield and Nitrogen Use Efficiency in Mechanical Pot-Seedling Transplanting Rice
Lin Li, Zheng Zhang, Tian Hua, Umair Ashraf, Yousef Alhaj Hamoud, Al Aasmi Alaa, Tang Xiangru, Duan Meiyang, Wang Zaiman, Pan Shenggang
Abstract
To assess the effects of straw return coupled with deep nitrogen (N) fertilization on grain yield and N use efficiency (NUE) in mechanical pot-seedling transplanting (MPST) rice, the seedlings of two rice cultivars, i.e., Yuxiangyouzhan and Wufengyou 615 transplanted by MPST were applied with N fertilizer at 150 kg/hm2 and straw return at 6 t/hm2 in early seasons of 2019 and 2020. The experiment comprised of following treatments: CK (no fertilizer and no straw return), MDS (deep N fertilization and straw return), MBS (broadcasting fertilizer and straw return), MD (deep N fertilization without straw return), MB (broadcasting fertilizer without straw return). Results depicted that the MDS treatment significantly increased the rice yield by 41.69%–72.22% due to total above-ground biomass, leaf area index and photosynthesis increased by 54.70%–55.80%, 38.52%–52.17% and 17.89%–28.40%, respectively, compared to the MB treatment. In addition, the MDS treatment enhanced the total N accumulation by 37.74%–43.69%, N recovery efficiency by 141.45%–164.65%, N agronomic efficiency by 121.76%–134.19%, nitrate reductase by 46.46%–60.86% and glutamine synthetase by 23.56%–31.02%, compared to the MB treatment. The average grain yield and NUE in both years for Yuxiangyouzhan were higher in the MDS treatment than in the MD treatment. Hence, deep N fertilization combined with straw return can be an innovative technique with improved grain yield and NUE in MPST in South China.