Effects of nitrogen rate on growth, grain yield, and nitrogen utilization of multiple cropping proso millet after spring-wheat in Irrigation Area of Ningxia
摘要
<p id="C3">The objective of this study is to clarify the growth rule, yield, and nitrogen utilization efficiency of proso millet under different nitrogen rates, the relationship between morphological characteristics and grain yield and nitrogen utilization was explored, and the suitable nitrogen rate for multiple cropping proso millet after spring-wheat in Irrigation Area of Ningxia was determined. The field experiments were conducted by single factor randomized block design, with four nitrogen rates [0 (N0), 90 (N1), 120 (N2), and 150 kg hm <sup>-2</sup> (N3)] were set in 2019, and six nitrogen rates [180 (N4) and 210 kg hm <sup>-2</sup> (N5) were added] in 2020. The results showed that the plant height, stem diameter, leaf area, root morphology, and dry matter accumulation at the key growth stages of proso millet were significantly promoted by nitrogen application, however, nitrogen application rate exceeded 150 kg hm <sup>-2</sup>, these indexes declined slightly except for the stem diameter and leaf area. With the increase of nitrogen rate, the root-shoot ratio decreased first and then increased and then decreased slightly, and it reached the minimum under N2 treatment at most growth stages. The root-shoot ratio at jointing, heading, grain-filling and maturity stage under N2 treatment were 0.119, 0.087, 0.054, and 0.052, respectively. The grain yield, 1000-grain weight, and grain number per plant were significantly increased by nitrogen application, and with the increase of nitrogen application rate, the yield increased initially then slightly decreased, and achieved the best effect in N2 and N3 treatments. The grain yields of N2 and N3 treatments were 2979.41 kg hm <sup>-2</sup> and 3084.67 kg hm <sup>-2</sup>, respectively, which were 76.22% and 83.21% higher than those of N0 treatment. Nitrogen harvest index (NHI), nitrogen fertilizer apparent recovery rate (NRE), agronomic efficiency (NAE), and partial productivity (NPFP) under N2 treatment were 60.23%, 61.8