Rice Paddies Reduce Subsequent Yields of Wheat Due to Physical and Chemical Soil Constraints

Abstract

Yields of wheat crops that succeed rice paddy crops are generally low. To date, it has been unclear whether such low yields were due to rice paddies altering soil physical or mineral characteristics, or both. To investigate this quandary, we conducted field experiments in the Jianghan Plain to analyze differences in the spatial distribution of wheat roots between rice-wheat rotation (RW) and dryland-wheat rotations (DW) using a range of nitrogen treatments. Dryland wheat crops were preceded by either dryland soybean or corn in the prior summer. Biomass of wheat crops in RW systems was significantly lower than that of DW for all N fertilizer treatments, although optimal nitrogen management resulted in comparable wheat yields in both DW and RW. Soil saturated water capacity and non-capillary porosity were higher in DW than RW, whereas soil bulk density was higher in RW. Soil available nitrogen and organic matter were higher in DW than RW irrespective of N application, while soil available P and K were higher under RW both at anthesis and post-harvest stages. At anthesis, root length percentage (RLP) was more concentrated in surface layers (0–20 cm) in RW, whereas at 20–40 cm and 40–60 cm, RLP was higher in DW than RW for all N treatments. At maturity, RLP were ranked 0–20 > 20–40 > 40–60 cm under both cropping systems irrespective of N fertilization. Root length percentage and soil chemical properties at 0–20 cm were positively correlated (r = 0.79 at anthesis, r = 0.68 at post-harvest) with soil available P, while available N (r = −0.59) and soil organic matter (r = −0.39) were negatively correlated with RLP at anthesis. Nitrogen applied at 180 kg ha−1 in three unform amounts of 60 kg N ha−1 at sowing, wintering and jointing resulted in higher yields than other treatments for both cropping systems. Overall, our results suggest that flooding of rice paddies increased bulk density and reduced available nitrogen, inhibiting the growth and yield of subsequent wheat crops relative to rainfed corn or soybean crops.

Impact of Rice–Wheat Straw Incorporation and Varying Nitrogen Fertilizer Rates on Soil Physicochemical Properties and Wheat Grain Yield

“…Straw returning is an efficacious method which is being promoted for addressing the excessive straw generation and for mitigating the environmental pollution associated with straw burning. Previous studies have demonstrated that the practice of returning straw to the field significantly impacts on the physicochemical properties of the soil, as well as on the microbial community [3,15,41]. The findings of our study indicate that the varied rates of nitrogen application and rice straw return differentially impacted soil physicochemical properties and wheat growth at the different growth stages, and thus influenced wheat grain yield (Tables 1-3).…”

“…The field is used for wheat and rice rotation. The Jianghan Plain is one of major grain production bases in Hubei Province, and forms a key part of the wheat-growing areas in the Yangtze River Basin [41]. The Experimental Farm Station is characterized by a typical subtropical monsoon climate in the middle-lower Yangtze River Basin of China.…”

Current State and Limiting Factors of Wheat Yield at the Farm Level in Hubei Province

“…The yield difference between different cropping systems is mainly caused by differences in the soil environment [23]. In the water and drought rotation system, the soil surface structure formed in the rice season and the compact plow layer formed over the years result in significant differences in soil structure between the wheat planted after rice and the wheat planted in dryland [24].…”