Negative and Positive Impacts of Rape Straw Returning on the Roots Growth of Hybrid Rice in the Sichuan Basin Area

Abstract

Incorporating oilseed-rape straw in soil is one of the effective methods for enhancing the use efficiency of agricultural resources in the rape-rice rotation system. However, the impacts of oilseed-rape straw incorporation on root growth and dynamic changes in soil are still unclear. In order to provide a deeper understanding of the oilseed rape straw return on rice growth and productivity, the experiment was conducted in the field and in a specially-designed pots system from 2016 to 2017 by means of two straw returning methods and four straw returning amounts. In the early stage of rice growth (0–36 days after rice transplanting) the straw returning treatments decreased 1.0–8.6 mg/plant in bleeding density and 0.10–6.11, 0.06–0.31, and 0.52–0.84 μmol/(g h) in the activity of glutamine synthetase (GS), glutamic-oxalacetic transaminase (GOT), and glutamic-pyruvic transaminase (GPT), respectively. Oilseed rape straw returned by mulching induced negative impacts on new germinating roots in 0–10 cm of soil, while the negative impacts were observed on roots in 10–30 cm of soil for straw returned by plowing. In the later stage of rice growth (56–75 days after rice transplanting), oilseed rape straw returning produced some positive impacts on rice roots, which enhanced the yield of rice. Conclusively, our findings suggested that dynamic root growth and the activity of root enzymes are two major factors behind the slow reviving of rice after transplanting in the straw returning field. Plowing is a more appropriate method of straw returning than mulching in the rape-rice rotation system in the Sichuan basin area, with a straw incorporation rate of 3.0 t/hm2.

Oilseed rape straw returning changes soil reducibility and affects the root and yield of rice in the rape‐rice rotation field at Sichuan Basin area of China

“…Straw is a comparatively abundant resources in China, producing 0.79 billion tons of straw annually (Zou et al., 2016). Considering from effective use of straw resources, more and more straw retuned into soil, especially in rape‐rice rotation system (Wang et al., 2019). Previous research has shown that the continuous introduction of oilseed‐rape straw into soil has created a better growth environment for rice yield by raising nitrogen, phosphorus, potassium (Yin, Zhao, Li, Cheng, & Liu, 2018), and soil organic matter content (Singh, Jalota, & Singh, 2007; Zhang, Hu, Li, Zheng, & Li, 2017).…”

“…Lots of research reported positive impacts of straw incorporation on rice production in China, Asia and in the world wide, considering in a long period. With the development of harvest machine, more than 43.7% of the total rape straw in China has returned into soil (Wang et al., 2019), which cause the organic matter of rice field increased from 1.08% in 1990 to 2.56% in 2019 (Yin et al., 2018; Zhang et al., 2017). A 10 years study of the rice‐wheat rotation system in India showed a significantly increasing of phosphorus, potassium in soil, which caused the yield increase 4.6–10.4% of wheat and 3.8–10.2% of rice in straw returning treatment than straw burned treatment (Gupta, Ladha, Singh, Singh, & Pathak, 2007; Nandan et al., 2018).…”

“…Due to the depletion of oxygen by straw fermentation, a strict oxygen deficiency environment built in flooded soil, which produced yellow leaves, dark roots and slowly root development in early seasons of rice growth (Narteh et al., 1997; Ruensuk et al., 2010) . The Large ratio of C/N in straw lead to a large nitrogen consumption, during the straw decomposing process, which will produce a biological nitrogen competition effect on rice growth (Wang et al., 2019). Fimognari, Lenzi, and Hrelia (2008) showed that increasing basal and tillering fertilizer inputs can relieve the negative impacts of straw returning on rice dry matter and grain yield.…”

“…Variation of soil physical and chemical properties, caused by straw returning, obviously affect the growth of rice root, particularly the morphology and behavior of the rice root growth (Huang, Ju, & Yang, 2017). Due to straw incorporation, the rice root growth rate decreased 5.1–9.3% than with no straw returning treatments during 0–36 d after rice transplanted (Wang et al., 2019). It is believed that root development and rice root hormones play a key role in the rice root growth cycle, and a great deal of attention has been paid to increase grain yields by improving rice root distribution, structure and function in modern rice root cultivars (Gu et al., 2018; Oyanagi et al.,1994; Samejima et al., 2005; Su et al., 2014; Sun, Lu, Yu, Kronzucker, & Shi, 2016; Uga et al., 2013).…”

“…It is believed that root development and rice root hormones play a key role in the rice root growth cycle, and a great deal of attention has been paid to increase grain yields by improving rice root distribution, structure and function in modern rice root cultivars (Gu et al., 2018; Oyanagi et al.,1994; Samejima et al., 2005; Su et al., 2014; Sun, Lu, Yu, Kronzucker, & Shi, 2016; Uga et al., 2013). Some results have indicated that competitive rice root development and root enzyme activity are two major factors behind the slow revival of rice growing in rape straw returning field (Uga et al., 2013; Wang et al., 2019). However, there is currently not so much research on the long‐term effects of straw returning on soil reducibility and its impacts on rice root growth.…”