Optimization of row and hill spacing patterns improved rice population structure and increased rice yield

Abstract

Objective: The objective of this study was to investigate the effects of row and hill spacing patterns on rice populations during mechanized production, material accumulation and transport, and photosynthetic characteristics and to explore the role of these factors in improving rice yield.

Methods: An field experiment was conducted from 2022 to 2023 with Liaojing 419 as the test material under four planting modes: LFM: local farmer cultivation mode was used as a control; and CDM: conventional densification mode; NDM: narrow row densification mode; and WNDM: wide narrow row densification mode were used as the treatment modes. Field mechanized transplantation experiments were conducted to investigate the effects of plant pattern on the physiological and morphological characteristics of rice plant individuals and populations, and clarify the relationships of physiological and biochemical changes with row and hill spacing.

Results: The result shows that WNDM presented the greatest yield advantage in the two years trial, with yield significantly greater than that of the local farmer mode and other densification modes, with an increase of more than 8% compared with LFM. The reciprocal second leaf yielded the highest values, at 27.33 μmol·m^-2·s^-1 and 27.13 μmol·m^-2·s^-1under the WNDM over two years, which were significantly higher than those of the other modes. The WNDM resulted in the greatest accumulation of biomass during the heading-maturity stage, with values of 6.23 t/ha and 6.07 t/ha, respectively. Compared with the LFM, the WNDM had higher biomass at maturity, at 23.64 t/ha and 23.75 t/ha for two years, an increase of 17.90% and 17.87%, respectively. The sugar spikelets ratio was highest under the WNDM, which was significantly greater than those in the CDM and NDM.

Conclusions: The wide narrow row densification mode of mechanized transplanting not only improved yield but also effectively optimized the population spatial distribution, improved resource utilization efficiency, and presented high production adaptability and promotion potential.

Significance: This study provides theoretical and practical references for improving rice production efficiency and promoting high-quality mechanized processes in Northeast China, which is highly important for achieving sustainable development in modern agriculture.

Keywords: population structure; rice; rice yield; row and hill spacing patterns; wide narrow row densification mode.

Figure 1

Meteorological data of rice growth period in the experimental site.

Figure 2

Effects of hill and row distances on actual rice yield. A one-way analysis of variance (ANOVA) followed by least significant difference (LSD) multiple range test was per-formed to evaluate the statistical differences among the treatments per each parameter measured. Different uppercase letters and lowercase letters indicate significant difference at P< 0.05 and P< 0.01 probability level in a year, respectively. * indicates the P< 0.05, ** indicates the P< 0.01, ns indicates no significant.

Figure 3

Productive panicles rate. A one-way analysis of variance (ANOVA) followed by least significant difference (LSD) multiple range test was per-formed to evaluate the statistical differences among the treatments per each parameter measured. Different uppercase letters and lowercase letters indicate significant difference at P< 0.05 and P< 0.01 probability level in a year, respectively.

Figure 4

Tiller capacity. A one-way analysis of variance (ANOVA) followed by least significant difference (LSD) multiple range test was per-formed to evaluate the statistical differences among the treatments per each parameter measured. Different uppercase letters and lowercase letters indicate significant difference at P< 0.05 and P< 0.01 probability level in a year, respectively.

Figure 5

Tiller formation. A one-way analysis of variance (ANOVA) followed by least significant difference (LSD) multiple range test was per-formed to evaluate the statistical differences among the treatments per each parameter measured. Different uppercase letters and lowercase letters indicate significant difference at P< 0.05 and P< 0.01 probability level in a year, respectively.

Figure 6

Biomass accumulation. A one-way analysis of variance (ANOVA) followed by least significant difference (LSD) multiple range test was per-formed to evaluate the statistical differences among the treatments per each parameter measured. Different uppercase letters and lowercase letters indicate significant difference at P< 0.05 and P< 0.01 probability level in a year, respectively.

Figure 7

Nonstructural carbohydrate (NSC) content in stems and sugar spikelets ratio at heading to NSC remobilization. A one-way analysis of variance (ANOVA) followed by least significant difference (LSD) multiple range test was per-formed to evaluate the statistical differences among the treatments per each parameter measured. Different uppercase letters and lowercase letters indicate significant difference at P< 0.05 and P< 0.01 probability level within a column in a year, respectively.

Figure 8

Correlations between agronomic traits. AY is actual yield, PPN is productive panicles number, FGN is full grains number, TSN is total spikelets number, SSR is seed setting rate, TSW is thousand seeds weight, TN is stems number of transplanting stage, JN is stems number of jointing stage, HN is stems number of heading stage, PPR is productive panicles rate, PR-FL is photosynthetic rate of flag leaf, PR-RSL is photosynthetic rate of reciprocal second leaf, PA-JH is phase accumulation of jointing to heading, PA-HM is phase accumulation of heading to maturity, LAI-J is leaf area index of jointing, LAI-H is leaf area index of heading, LAI-J is leaf area index of maturity, PP-JH is photosynthetic potential of jointing to heading, PP-HM is photosynthetic potential of heading to maturity, NA-JH is net assimilation of jointing to heading, NA-HM is net assimilation of heading to maturity, NSCA-H is NSC accumulation of heading, NSCA-M is NSC accumulation of maturity. * indicates P< 0.05, ** indicates P< =0.01.

Figure 9

Interrelatedness map showing the potential mechanisms of row and hill spacing patterns to improve rice yield by regulating agronomic traits. A red arrow with a “+” indicates a positive effect; a blue arrow with a “−” indicates a negative impact. The solid line denotes that the impact is statistically significant, and the thicker the line, the greater the impact. The dotted line indicates that the impact is not statistically significant. * = significant at p< 0.05; ** = significant at p< 0.01.