Mechanical dry direct-sowing modes improving growth, development and yield of rice

Abstract: In order to clarify yield formation mechanism of mechanical dry direct-sowing rice, the objective of this experiment was to study the effects of different mechanical dry direct-sowing modes on growth and development characteristics and yield of rice. Two different rice cultivars of indica hybrid rice F you 498 (143 days growth duration) and conventional japonica rice Xudao 4 (145 days growth duration) were planted with two mechanical dry direct-sowing modes, including a shallow rotary tillage land and mechanic drilling simultaneously (B1), regulating soil moisture and two rotary tillage before mechanic drilling (B2). Manual broad-cast sowing (B3) was set as control at the same time. We investigated and performed growth analysis during different growth periods, and determined yield formation and physiological characteristics under different direct-sowing treatments. The dry direct-sowing machine in this study was modified by Nanjing Agricultural University and was re-modified by Sichuan Agricultural University. This machine has six drills and sowed depth 2.0 cm, drill spacing 28.0 cm, working area 1.50 m. Motive power of this machine was the Shanghai New Holland tractor (SNH504). This test adopted row spacing 20 m × 1.5 m, each plot covered 30 m2 of seeding amount was 30.0 kg/hm2 of indica hybrid rice F you 498, 37.5 kg/hm2 of conventional japonica rice Xudao 4 respectively. The nitrogen fertilizer amount was 180 kg/hm2, and the amount of potash and phosphate were 90 and 180 kg/hm2, respectively. The N application ratios was applied on 4 splits: 50% basal, 30% tillering fertilizer at the third leaf stage, 10% panicle N-fertilizer at the 4th leaves emerged from the top, 10% ear granular fertilizer at the full heading stage. The phosphate fertilizer was applied as base fertilizer. The potash fertilizer application ratio of basic fertilizer, tillering fertilizer and ear granular fertilizer was 2:1:1. The other management measures were at a uniform with high-yield cultivation. The results showed that the variety difference and direct-sowing modes significantly affected dry matter accumulation and leaf area index (LAI) at the mainly growth periods, net photosynthetic rate (Pn) and protective enzyme activities of flag leaves, root bleeding intensity, culm lodging resistance during the grain filling stage and the grain yield. Under different direct-sowing modes, the various indicators on yield and growth characteristics of F you 498 were significantly higher than those of Xudao 4. Compared with B3 treatment, rice under mechanical direct-seeding modes could optimize the number of rice tillering, improve the percentage of earbearing tiller, maintain an appropriate LAI and increase efficient leaf area ratio at the full-heading stage. Besides mechanical direct-seeding could improve photosynthetic capacity at the grain filling stage and therefore increase the accumulation of photosynthetic products. In addition, Pn and protective enzyme activities in flag leaves, root bleeding intensity, culm lodging resistance during the grain filling stage under mechanical direct-seeding modes were superior, and rice could gain higher seed-setting rate and 1000-grain weight with a number of effective panicles. These outstanding traits should be the important reason for mechanical direct-sowing rice further to increase yield. Under different mechanical direct-sowing modes, compared with B3, B2 treatment was the best model in this study referred as the mechanical direct-sowing treatments, which could further promote the dry matter accumulation, alleviate LAI decay, increase root vigor and the ability of culm lodging resistance during grain filling stage, consequently, promoting the seed-setting rate and 1000-grain weight as well as the grain yield.