Gao Yang, Chen Jinsai, Wang Guangshuai, Liu Zhandong, Sun Weihao, Zhang Yingying, Zhang Xiaoxian
Farmland Irrigation Research Institute, Chinese Academy of Agricultural Sciences, Xinxiang, China.
Department Sustainable Agriculture Science, Rothamsted Research, Harpenden, United Kingdom.
Front Plant Sci. 2022 Jun 24;13:918043. doi: 10.3389/fpls.2022.918043. eCollection 2022.
Modifying farming practices combined with breeding has the potential to improve water and nutrient use efficiency by regulating root growth, but achieving this goal requires phenotyping the roots, including their architecture and ability to take up water and nutrients from different soil layers. This is challenging due to the difficulty of root measurement and opaqueness of the soil. Using stable isotopes and soil coring, we calculated the change in root water uptake of summer maize in response to planting density and nitrogen fertilization in a 2-year field experiment. We periodically measured root-length density, soil moisture content, and stable isotopes δO and δD in the plant stem, soil water, and precipitation concurrently and calculated the root water uptake based on the mass balance of the isotopes and the Bayesian inference method coupled with the Markov Chain Monte Carlo simulation. The results show that the root water uptake increased asymptotically with root-length density and that nitrogen application affected the locations in soil from which the roots acquired water more significantly than planting density. In particular, we find that reducing nitrogen application promoted root penetration to access subsoil nutrients and consequently enhanced their water uptake from the subsoil, while increasing planting density benefited water uptake of the roots in the topsoil. These findings reveal that it is possible to manipulate plant density and fertilization to improve water and nutrient use efficiency of the summer maize and the results thus have imperative implications for agricultural production.
结合育种改良种植方式，有可能通过调节根系生长来提高水分和养分利用效率，但要实现这一目标需要对根系进行表型分析，包括其根系结构以及从不同土壤层吸收水分和养分的能力。由于根系测量困难以及土壤不透明，这一过程具有挑战性。在一项为期两年的田间试验中，我们利用稳定同位素和土壤取芯技术，计算了夏玉米根系水分吸收对种植密度和氮肥施用的响应变化。我们定期同时测量根长密度、土壤含水量以及植物茎、土壤水分和降水中的稳定同位素δO和δD，并基于同位素质量平衡以及结合马尔可夫链蒙特卡罗模拟的贝叶斯推理方法计算根系水分吸收量。结果表明，根系水分吸收量随根长密度呈渐近增加，氮肥施用对根系获取水分的土壤位置影响比种植密度更为显著。特别是，我们发现减少氮肥施用量可促进根系下扎以获取底土养分，从而增强其从底土吸收水分的能力，而增加种植密度有利于表层土壤中根系的水分吸收。这些发现表明，通过调控种植密度和施肥量来提高夏玉米的水分和养分利用效率是可行的，因此这些结果对农业生产具有重要意义。
