Effects of sowing date and nitrogen application rate on dry matter accumulation, yield, N uptake and utilization by peanut

Objectives This study examines the effects of sowing date and N application rate on yield, dry matter accumulation, N absorption and utilization by two peanut cultivars under field conditions. The aim was to provide technical support for peanut’s high yield and efficient resource utilization.

Methods The common large peanut cultivar, Huayu 22 , and the high oleic acid peanut cultivar Jihua 16, were used as the research materials in a field experiment. There were four sowing dates set: April 30 (SD1), May 10 (SD2), May 20 (SD3), and May 30 (SD4), with three N application rates of 0, 120, and 240 kg/hm² (N0, N120, and N240). The plant’s dry matter accumulation and chlorophyll content were analyzed at the seedling, flower needle, pod setting, full fruit, and maturity stages. Further, the N content in different organs, and kernel quality were analyzed at the maturity stage.

Results 1) Sowing date and N application rate significantly (P<0.05) affected the yield and yield composition of peanuts. The pod number per plant and 100-pods weight decreased gradually with the delay of the sowing date. Compared with SD2, SD3, and SD4, the pod yield of SD1 increased by 5.5%–7.3%, 12.8%–20.2%, and 30.7%–44.9%, respectively. Nitrogen application (P<0.05) increased the pod number per plant by 15.9%～33.3% and 100-pods weight by 5.9%–7.1%. The yield of Huayu 22 increased first and then decreased with the increasing of N application rate. The highest yield was recorded under N120, which was 6.1% higher than N240, but the yield of Jihua 16 increased with the increasing of N application rate. 2) By delaying the sowing date, the crude fat content of Huayu 22 and Jihua 16 decreased gradually, while N application increased the crude protein and fat content of peanut kernel. 3) The dry matter accumulation of early sowing peanuts was slower at the early growth stage and accelerated later with an increased pod rate. The growth characteristics of late sowing peanuts opposed that of early sowing. The dry matter accumulation of different sowing dates at maturity was SD1>SD2> SD3>SD4. N application rate (P<0.05) increased leaf SPAD and dry matter accumulation across the growth stages. It also increased the distributed proportion of dry matter in pods by 6.9%–8.7%. However, it reduced the distribution of dry matter in the roots, stems, and leaves. 4) Proper early sowing and N application promoted N absorption by plants, and increased N concentration in the roots, stems, leaves and pods. The N accumulation in early sowing peanut plants was higher than that of late sowing, and the proportion of N allocated to pods was high. The N accumulation in each organ and the proportion of N distribution in pod increased with increasing N application rate, but there was no significant difference (P>0.05) between N120 and N240 for the proportion of N distribution in pod. 5) The agronomic efficiency and partial factor productivity of N fertilizer of the two peanut cultivars decreased with the delay of sowing date and increasing N application rate. The partial factor productivity of SD1 was higher than SD2, SD3, and SD4 by 5.3%–6.8%, 12.5%–19.6%, and 31.4%–45.7%, respectively.

Conclusions The suitable sowing date and N application rate for the two cultivars of peanuts were April 30 to May 10 and N 120 kg/hm². This technical condition was conducive to peanut plant growth and nitrogen absorption, improved dry matter and nitrogen accumulation, increased the number of pods per plant and 100-pods weight, and improved pod yield and nitrogen use efficiency.