Effects of Dense Planting with Less Basal N Fertilization on Rice Yield, N Use Efficiency and Greenhouse Gas Emissions

Abstract

Rice cropping innovations for high yield with high N use efficiency (NUE) and low greenhouse gas (GHG) emissions are significant in ensuring food security and coping with climate change. The objective of this study was to investigate the comprehensive effects of dense planting with less basal N application (DR) on rice yield, NUE and GHG emissions. Field experiments were conducted at three sites in China: Shenyang, Danyang and Jinxian representing annual single rice cropping system, wheat-rice cropping system and double rice cropping system, respectively. Four planting densities with 25, 50, 75 and 100% higher each time correspondingly with about 25, 50, 75 and 100% less in basal N rate (i.e., DR1, DR2, DR3 and DR4 correspondingly) relative to traditional cropping for high yield (CK). Across three tested sites, the DR1 mode showed a large potential of NUE enhancement by 19.6% and GHG emissions mitigation by 12.2% at area-and yield-scaled with similar rice yield compared to the CK. However, further increase in planting density and decrease in basal N application caused a significant reduction in rice yield with a large increase in GHG emissions. Our results will provide important reference to rice cropping innovations for the integrated goals of food security, environmental health and climate change mitigation in China.

Effects of Planting Density and Nitrogen Application on Soil Greenhouse Gas Fluxes in the Jujube–Alfalfa Intercropping System in Arid Areas

“…This experimental study showed that GHGs fluxes exhibited lower emissions at the D2 density level (Figures 3-5), indicating that appropriately increasing the alfalfa density is beneficial to reducing GHGs emissions in the jujube-alfalfa intercropping system. The CH4 emissions of the jujube-alfalfa intercropping system varied from −0.33 to 0.072 mg m −2 h −1 , and the appropriate alfalfa density exerted a certain deposition effect on the atmospheric CH4 uptake, which was similar to the results of the study on rice by Zhu Xiangcheng et al [32]. A large number of studies have shown that excessive nitrogen fertilizer inputs are the main factors contributing to GHG emissions from agricultural fields [13,33], and methods for optimizing the nitrogen inputs in cropping systems have become a primary issue in reducing GHs emissions from fields [34].…”

“…This experimental study showed that GHGs fluxes exhibited lower emissions at the D2 density level (Figures 3-5), indicating that appropriately increasing the alfalfa density is beneficial to reducing GHGs emissions in the jujube-alfalfa intercropping system. The CH 4 emissions of the jujube-alfalfa intercropping system varied from −0.33 to 0.072 mg m −2 h −1 , and the appropriate alfalfa density exerted a certain deposition effect on the atmospheric CH 4 uptake, which was similar to the results of the study on rice by Zhu Xiangcheng et al [32].…”

“…Meanwhile, a higher ST promoted alfalfa root respiration and increased microbial activity, which, in turn, increased the soil respiration intensity. The model of increasing density and reducing nitrogen has been proven to be beneficial for GHG emission reduction: on the one hand, it reduces the amount of nitrogen applied, which indirectly reduces the carbon emissions of nitrogen fertilizer in various links, such as production, transportation, and storage; on the other hand, it directly reduces CH 4 and N 2 O emissions [32]. This experimental study showed that GHGs fluxes exhibited lower emissions at the D2 density level (Figures 3-5), indicating that appropriately increasing the alfalfa density is beneficial to reducing GHGs emissions in the jujube-alfalfa intercropping system.…”

Lower‐than‐expected CH4 emissions from rice paddies with rising CO2 concentrations

“…Plastic pots (diameter, 22 cm; height, 20 cm) were filled with 4.5 kg of air-dried soil. The diameter and height of the pots reflect common rice transplant density (25 cm × 15 cm per plant) and plow layer depth (0-15 cm) in paddy fields (Chu, Chen, Wang, Yang, & Zhang, 2014;Zhu et al, 2015). We transplanted two healthy rice seedlings into each pot, using six pots per treatment combination.…”

Can optimizing seeding rate and planting density alleviate the yield loss of double‐season rice caused by prolonged seedling age?

“…Numerous studies have reported that reasonably dense planting was beneficial to improve rice yield associated with the increase of panicle number (Huang et al., 2013; Islam et al., 2013; Zhao et al., 2013). In addition, some studies found that increasing the planting density could compensate for the negative effect of reducing nitrogen rate on rice yield (Hou et al., 2019; Zhu et al., 2015). However, it is not clear whether increasing the planting density can alleviate the yield loss caused by prolonged seedling age.…”