Effects of spacing-adjustable wide-narrow row on growth characteristics and yield of machine-transplanted mid- and late- season rice

Abstract: In order to investigate the effects of different row spacing on the growth characteristics and yield of single cropping medium rice and double cropping late rice, single cropping medium rice (Fengliangyouxiang No.1 and Huiliangyou 898) and double cropping late rice (Zhendao No.18 and Shangnongjing No.2) were machine-transplanted in five row spacing: three narrow-wide rows of 20 cm+30 cm, 25 cm+30 cm and 25 cm+35 cm, and 2 uniform rows of 25 cm and 30 cm. The plant height, leaf area index, tiller dynamics, dry matter weight, yield and component factors of rice were compared among five rows spacing. The results showed that: 1) The row spacing had no significant effect on plant height at each growth period, but had significant effect on leaf area index, number of tillers and dry matter quality (P<0.01). The effect of row spacing on these traits depended on the types of cultivars used. The leaf area index of 4 rice varieties was affected by row spacing at the jointing stage, booting stage, heading stage and maturity stage, but the degree of influence was different. The efforts of jointing and mature period were the most significant. The number of tillers and spike rate at each growth stage of single cropping medium rice was the highest in the narrow-wide row of 25 cm+35 cm, and gradually stabilized after the heading. The dry matter quality and growth rate of the single-cropping medium rice increased with the increase of row spacing, but double cropping late rice showed the opposite trend. 2) The average yield of different varieties of machine-transplanted rice was significantly different in row spacing and among varieties (P<0.05), but it was not significantly affected by different years. With the increase of the row spacing, the average yield of single cropping medium rice showed a trend of row spacing distribution Ⅴ>Ⅳ>Ⅲ>Ⅱ>Ⅰ. The average yield of row spacing distribution V (25 cm + 35 cm) of Fengliangyouxiang No.1 and Huiliangyou 898 was 0.74%-4.59% and 1.27%-5.58% higher than the other four kinds of row spacing distribution respectively. In contrast, the average yield of double cropping late rice showed a trend of row spacing distribution Ⅱ>Ⅰ>Ⅲ>Ⅴ>Ⅳ. The average yield of row spacing distribution Ⅱ(20 cm+30 cm) of Zhendao No.18 and Shangnongjing No.2 was 0.10%～14.09% and 1.02%～7.67% higher than the other 4 kinds of row spacing distribution respectively. The average yield ranking of 4 rice varieties in 2 a experiments was as follows: Fengliangyouxiang No.1 (8624.4 kg/hm2)>Zhendao No.18 (8 294.8 kg/hm2)>Huiliangyou 898(8 202.9 kg/hm2)>Shangnongjing No.2 (6 827.2 kg/hm2). 3) Among the factors of yield composition, the effective panicles (coefficient of variation 1.93% to 7.50%), grain number of panicle (coefficient of variation 1.58% to 6.08%) and seed setting rate (coefficient of variation was 0.86% to 4.54%) were influenced greatly by row spacing, and the row spacing had less influence on 1000-grain weight (coefficient of variation was 0.81% to 2.70%) and spike length (coefficient of variation was 0.89% to 2.82%). In addition to no significant correlation between 1000-grain weight and yield, the spike length, grain number of panicle and seed setting rate of 4 varieties had obviously positive correlation with yield. In the region along the Yangtze River and Jianghuai region in Anhui Province, the narrow-wide rows distribution of 25 cm+35 cm should be recommended for single cropping medium rice varieties, and narrow-wide rows distribution of 20 cm+30 cm should be selected for double cropping late rice varieties, which is conducive to promoting the quality and high yield of different types of rice varieties. The results indicated the laws of yield formation of different types of machine-transplanting rice in different row spacing distributions, which can provide the reference for selection of machine-transplanted varieties and setting of machine-transplanted row spacing for single cropping medium rice and double cropping late rice in the above regions.