Abstract
In order to investigate the feasibility of using rice leaf critical nitrogen concentration as a nitrogen nutrition diagnosis index, a three-year positioning experiment with large-spike rice cultivar (Wuyoudao4) and multiple-spike rice cultivar (Songjing9) under five nitrogen levels (0, 60, 120, 180, and 240 kg·ha−1) was conducted. A critical nitrogen dilution curve and a nitrogen nutrition index (NNI) of rice leaf dry matter were constructed for Wuyoudao4 (Nc = 1.96LDM−0.56, R2 = 0.87, NNI was between 0.6–1.26, and Normalized Root Mean Square Error (n-RMSE) = 13.07%) and Songjing9 (Nc = 1.99LDM−0.44, R2 = 0.94, NNI was between 0.64–1.29, and n-RMSE = 15.89%). The relationship between dry matter and nitrogen concentration of rice leaves was a negative power function, and the model had good stability over the three years. The developed critical nitrogen concentration dilution curve, based on leaf dry matter, was able to diagnose nitrogen nutrition in rice efficiently. The model established in this study could be used to directly regulate and control the nitrogen nutrition of rice leaves.
Highlights
Heilongjiang Province is the main region for japonica rice production and is a significant commercial food base for China
N application rates exhibited a significant effect on leaf dry matter throughout the growth period, ranging from minimum value of effect
The SPAD technique is determined by leaf color and was appropriate and easy to use
Summary
Heilongjiang Province is the main region for japonica rice production and is a significant commercial food base for China. The yields of japonica rice from Heilongjiang can reach up to. In order to improve people’s lives, we need to improve the yield and quality of rice. The high-quality aromatic japonica rice, Wuyoudao, is prone to lodging and yield reduction due to improper water and fertilizer management. In order to fully meet the growth needs of rice, excessive nitrogen fertilizer is applied [2]. Proper nitrogen fertilizer application is necessary to improve rice yield, excessive nitrogen fertilizer application leads to a high cost of production. To realize rational fertilization of rice scientifically, it is necessary to find the critical point of nitrogen demand that can maximize rice yield with the lowest amount of nitrogen applied
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