Effects of planting density and NPK-fertilization level on lodging resistance and grain yield of common buckwheat

Abstract

Context or problem

Increasing planting density and fertilization rates have been widely used to enhance common buckwheat yield. However, it also led to higher lodging rates and severity.

Objective or research question

The aim of this study was to determine the mechanism of the interaction between planting density and fertilization level on lodging characteristics and yield of common buckwheat.

Methods

Common buckwheat variety XN D4103 was used as the experimental material, and split-plot design was adopted to study lodging related traits and yield under two planting densities (D1: 9.0 ×10⁵, D2: 1.35 ×10⁶ plants·hm² respectively) and three fertilization levels (F1: 120 (N), 76.8 (P₂O₅) and 56.4 (K₂O) kg·hm²; F2:180 (N), 115.2 (P₂O₅) and 84.6 (K₂O) kg·hm²; F3: 240(N), 153.6 (P₂O₅) and 112.8 (K₂O) kg·hm², respectively).

Results

Results showed: (1) Increasing the planting density resulted in a decrease in total root length, total root surface area, average root diameter, and root tip number. However, the medium level of fertilizer application effectively enhanced the root morphological indexes at different growth stages. (2) Increased planting density resulted in a decrease in diameter, plumpness, and snapping resistance of the basal 2nd internode. However, the anatomical structure and chemical composition were improved at the medium fertilization level, leading to a significant increase in snapping resistance. (3) With higher planting density and fertilizer application, the plant height, center of gravity height, length of basal 2nd internode, culm fresh weight, and lodging index increased, thereby increasing the risk of lodging. (4) lodging rate was significantly and positively correlated with the length of basal 2nd internode, plant height, height of the center of gravity and lodging index (P < 0.01), while significantly and negatively correlated with the morphological indexes of root, and the snapping resistance, anatomical structure, lignin-related enzymes (phenylalanine ammonia-lyase (PAL), 4-coumarate: CoA ligase (4CL), cinnamyl alcohol dehydrogenase (CAD)) activities, lignin content, cellulose content of culm (P < 0.01).

Conclusions

The recommended planting density is 1.35 × 10⁶ plants·hm², with a medium fertilizer application rate (N:180 kg·hm², P₂O₅:115.2 kg·hm², K₂O: 84.6 kg·hm²). Under these conditions, the lodging rate and classification are relatively low, while the yield reaches the maximum.

Implications or significance

This study provided a theoretical basis for establishing a high-yield and lodging-resistant cultivation of common buckwheat.