Effect of nitrogen application on yield, quality and light temperature physiological characteristics of summer peanut

Unreasonable application of nitrogen fertilizer leads to resource waste and affects the normal growth, development, yield, and quality of peanuts. The study aimed to investigate the impact of varying nitrogen application rates on the yield, quality, nitrogen accumulation dynamics, physiological characteristics to light and temperature, and root morphology of summer peanuts. The findings aim to offer insights for the efficient and scientific application of nitrogen fertilizers in peanuts. A field experiment on nitrogen fertilizer application was conducted in Wenxian County, Jiaozuo City, Henan Province, from 2021 to 2022. The tested variety was ‘Yuhua 22’ with five nitrogen fertilizer treatments of 0, 45, 90, 135, and 180 kg·hm⁻². The study assessed the yield and quality indicators of summer peanut pods, at the mature stage, and the soil-plant analysis development (SPAD) value, canopy photosynthetic effective radiation, and canopy temperature were conducted at various stages namely the seedling, flowering-pegging, pod-setting, and pod-filling stages. Plant samples were collected to analyze nitrogen accumulation and root morphology. With an increasing nitrogen application rate, the peanut pod yield could be fitted by “linear + platform trends” in both years, with suitable nitrogen application rates of 150 and 113 kg·hm⁻², respectively. Nitrogen application increased the yield by an average of 18.86%. The crude protein, oil, and amino acid contents in grain at maturity first increased and then stabilized with an increasing nitrogen application rate. Compared to zero nitrogen application, the application of nitrogen led to notable effects, with average increases of 7.51%, 3.10%, and 10.08%, in crude protein, oil, and amino acid contents in grains respectively. The nitrogen accumulation amount of summer peanuts was fitted using nonlinear regression using a logistic equation. It was concluded that nitrogen application could increase the maximum and average accumulation rates, accelerate the rapid accumulation period, and promote the occurrence of peak absorption, thereby increasing the maximum nitrogen accumulation in peanuts and promoting sustainable and rapid growth of summer peanuts. The maximum, minimum, and mean canopy temperatures at each growth stage firstly decreased then increased with increasing nitrogen application rate; the SPAD value of peanut leaves and the photosynthetic active radiation and components of the canopy significantly increased with nitrogen application at 135 kg·hm⁻². The total root length, total root surface area, total root volume, and average root diameter of peanuts increased by 41.03%, 22.36%, 38.71%, and 12.19% at each growth stage after nitrogen application. The nitrogen fertilizer utilization efficiency was the highest under the nitrogen application rate of 135 kg·hm⁻². Meanwhile, increasing the nitrogen application rate gradually decreased agricultural efficiency and partial productivity. Reasonable nitrogen application can significantly increase the yield and quality of summer peanuts, promote nitrogen accumulation and utilization, and improve the physiological performance of light and temperature during growth. The recommended nitrogen application rate for summer peanuts under this test condition is 110−150 kg·hm⁻².