Effects of no-till and rice varieties on nitrogen and phosphorus balance in rice fields

Abstract

Background: Nutrient balance in rice paddy fields can change under different tillage management practices; however, the extent of the change may differ for various rice varieties. A field experiment was conducted over 2 successive years to clarify the effects of no-till and rice varieties on the apparent balance of nitrogen (N) and phosphorus (P). Four treatments: no-till/japonica rice (NTJ), no-till/glutinous rice (NTG), conventional tillage/japonica rice (CTJ), and conventional tillage/glutinous rice (CTG) with three replicates of each were established to test the hypothesis that no-till and japonica rice can improve the apparent balance of nutrients. Results: The tillage method and rice variety had interactive effects on the apparent balance of N and P. After the 2-year experiment, total N and P pools in the 20 cm surface soil layer were highest under the NTJ treatment (4757.0 kg N ha −1 , 2428.5 kg P ha −1) and lowest under the CTG treatments (4726.3 kg N ha −1 , 2412.0 kg P ha −1). Under no-till conditions, japonica rice had higher grain yield but lower straw biomass than that of glutinous rice. NTG treatment significantly increased the N and P content in rice grains and straw. The environmental losses of N and P in the rice fields mainly occurred during the rice season. Based on nutrient balance estimation, N losses in the NTJ, NTG, and CTJ treatments were reduced by 15.03 kg N ha −1 , 11.55 kg N ha −1 , 6.72 kg N ha −1 , respectively, as compared with that of the CTG treatment. The corresponding P losses were reduced by 8.02 kg P ha −1 , 7.84 kg P ha −1 , and 3.96 kg P ha −1. In terms of economic benefits, NTJ also resulted in the highest actual income (2724.25 US dollars) and the highest ratio of production investment (6.40). Conclusion: No-till was more likely to maintain soil N and P nutrients than conventional tillage, and this advantage was most significant when planting japonica rice. In addition, no-till was conducive to N and P uptake by rice, but only japonica rice exhibited increased grain yield. Consequently, the NTJ treatment was recommended to improve the N and P balance.

Plant productivity and nutrient uptake as affected by tillage and site‐position in furrow‐irrigated rice

“…In a study conducted in the Philippines (Julia et al., 2016), fertilized paddy fields had similar vegetative P concentrations as those measured in the current study. The presence of crop residues in the NT section of the study area likely facilitated elevated and stratified soil P at the soil surface, while the mixing action under CT likely distributed P more uniformly within the plow layer (Yang et al., 2020). Vegetative tissue uptake of N, P, and K in 2018 differed to some degree from the vegetative tissue concentrations measured in the same year (Table 2).…”

“…Averaged across tillage treatments, P uptake at the down‐slope position was 79.2 and 56.4% greater than at the up‐ and mid‐slope positions, respectively (Table 4). Similar to vegetative P concentration, the flooded conditions at the down‐slope position most likely favored P uptake from greater P availability (Yang et al., 2020). Although vegetative K concentrations differed among site positions in 2018, K uptake was unaffected by either tillage or site position in 2018 (Table 2) and averaged 129.6 (SE = 9.9) kg ha −1 across all treatments.…”

“…In contrast to N and results from 2018, vegetative P concentration in 2019 was 117 and 86% greater in the down‐slope than in the up‐ and mid‐slope positions, which did not differ (Table 4). The flooded‐soil conditions at the down‐slope position likely slowed P release from the pedosphere, thus likely increasing the duration of potential uptake and accumulation in the aboveground plant tissue (Yang et al., 2020).…”

“…Similar to vegetative P F I G U R E 1 Tillage (conventional tillage, CT; no-tillage, NT)-site position (up-slope, U; mid-slope, M; down-slope, D) combination effects on vegetative P concentration (g kg −1 ) in 2018 and vegetative Na concentration (mg kg −1 ) in 2019. Means (n = 3) within a panel with different letters are different at P < .05 concentration, the flooded conditions at the down-slope position most likely favored P uptake from greater P availability (Yang et al, 2020). Although vegetative K concentrations differed among site positions in 2018, K uptake was unaffected by either tillage or site position in 2018 (Table 2) and averaged 129.6 (SE = 9.9) kg ha −1 across all treatments.…”