Effect of Irrigation and Fertilization on Dry Matter Accumulation and Yield of Sunflower Modelled with the Richards’ Equation

Abstract

【Objective】 Soil water and nitrogen are the most important abiotic factors influencing plant growth and final yields. This paper aims to investigate the applicability of the Richards' equation for modeling growth, dry matter accumulation and yield formation of sunflower under different fertilizations and irrigations. 【Method】 The field experiment was conducted in 2021 in a dry area in the northern foot of Yinshan Mountain, Inner Mongolia. The variety Long Kui 27 used as the model plant; the field was mulched by plastic films. The split-plot experiment had three irrigation treatments: rain-fed plus irrigating 300 m3/hm2 of water just after the drilling to ensure seed germination (W1), replenishing irrigation by irrigating 900 m3/hm2 of water at seedling and budding stage, following the 300 m3/hm2 of pro-drilling irrigation (W2), and normal irrigation by irrigating a total 1 500 m3/hm2 of water at seedling, budding, flowering, and grain filling stages, respectively. In each irrigation treatment, there were three nitrogen fertilizations: 0 (N0), 135 (N1) and 270 kg/hm2 (N2). For each treatment, we used the Richards’ model to quantitatively analyze the changes in dry matter accumulation (DMA) and the impact of fertilization and irrigation on yield and yield formation. 【Result】 The Richards model was able to describe the dynamics of DMA. The impact of water and nitrogen on DMA and sunflower yield was obtained by the path analysis and the decision coefficient calculation. Optimized fertilization made the period of quick increase in DMA occur early, while excessive fertilization not only delayed the start of the quick increase in DMA but also shortened its duration. It was found that nitrogen application expedited the occurrence of the quick dry matter accumulation period, compared to no nitrogen application, while excessive nitrogen application not only brought the rapid growth period ending earlier, but also shortened it. Irrigation in the early growth stage delayed the onset of the rapid growth but increased the dry matter accumulation rate. In contrast, irrigation in the late growth stage delayed the end of the rapid growth period. 【Conclusion】 Our results provide guidance for optimal regulation of irrigation and fertilization to achieve high yield and improve water and nitrogen use efficiency of sunflower production in arid areas.

Keywords

• confectionary sunflower
• drip irrigation
• nitrogen fertilizer
• richards model