Reducing nitrogen rate and hill distance improves rice dry matter production in saline–alkali soils

Abstract

The integrated strategies for nitrogen management and planting density are important for improving rice (Oryza sativa L.) yield in saline-alkali soil; however, the optimal growth conditions for the Songnen Plain, China, are unclear. Here, we studied the effects of nitrogen application rate (NAR) (N0, 0 kg ha −1 ; N1, 90 kg ha −1 ; N2, 120 kg ha −1 ; N3, 150 kg ha −1 ; N4, 180 kg ha −1 ) and hill distance (HD) (HD1, 16.5 cm; HD2, 13.3 cm; HD3, 10 cm) on rice dry matter accumulation, translocation, and photosynthetic production in a split-plot experiment. At NARs below 120 kg ha −1 , the number of effective tillers increased significantly with increasing NAR and decreasing HD. The leaf area index (LAI) increased as the NAR increased and HD decreased and was the highest in the N4-HD3 treatment, followed by N3-HD3, at the full-heading stage. However, dry matter accumulation from the fullheading to the maturity stage was the highest in the N3-HD3 treatment. The population growth rate in N3-HD3 was the highest from the full-heading stage to the maximum grain-filling stage, at 26.46 g m −2 d −1 . The high rice yield under N3-HD3 conditions was attributed to the high dry matter accumulation after the full-heading stage and the high sheath output rate. This study revealed that treatment N3-HD3 resulted in high yield, from the perspective of photosynthetic matter production. INTRODUCTIONSoil salinity is an important limiting factor in agricultural production, currently affecting approximately 20% of the global arable land (Xia et al., 2019). China is one of the most seriously affected countries in the world, with large areas of

Responses of Rice Yield, N Uptake, NH3 and N2O Losses from Reclaimed Saline Soils to Varied N Inputs

“…The N uptake by rice was related to the N application rates, and N use efficiency generally decreased with an increase in the N application rate in sodic saline-alkaline rice paddies [24,31]. Our results show that with the increase in the N application rates, N uptake by rice shoot biomass increased and the N use efficiency of rice straw increased.…”

“…However, the N use efficiency of grain increased first and then decreased, reaching the peak in the N200 treatment. The field experiment on sodic saline-alkali soil at Songnen plain by Lv et al (2021) showed that the growth rate of stems was higher under low N treatment than that under high N treatment, which is significant for improving the dry matter of stems and prevent lodging at a low N level [31]. In other words, lodging maybe cause the loss of biomass at a high N level.…”