Responses of fragrant rice yield and quality to fertilization and climatic factors

Objectives Fragrant rice production is profitable, it has a unique taste and nutritional quality. Here, we studied fragrant rice's yield and quality response to chemical fertilizer application and climatic conditions to provide a reference for its efficient production across China.

Methods Literature was searched in CNKI and Google Scholar databases using the keywords “rice” , “aroma” , “fragrance” , “fragrant rice” , “fragrish rice” , and their combinations. A total of 501 sets of experimental data were extracted from the literature. We used the meta-analysis method to analyze the response of fragrant rice yield and quality to different fertilizer application rates and climatic conditions.

Results Applying N, P, and K fertilizer increased rice yield by 23.7%, 25.8%, and 18.0% on average. Compared with no N application, N application increased the yield of japonica and indica rice by 27.6% and 20.2%, respectively. Compared with no K application, K application increased the yield of japonica and indica rice by 29.9% and 7.3%, respectively. N and K fertilization (P<0.05) increased the milling (head rice rate) and cooking quality (crude protein content, gel consistency) of fragrant rice. Further, K application improved fragrant rice appearance (chalkiness) and aroma quality (2-AP content). N application exhibited (P<0.05) quality effect on conventional indica fragrant rice, while K application improved indica hybrid fragrant rice's quality. Under N application conditions, the whole head rice rate generally increased with enhanced effective accumulated temperature during the growing period. The values increased at first and then decreased with increasing accumulated precipitation and sunshine hours. The gel consistency initially showed a decreasing trend, and increasing with increased accumulated temperature, precipitation, and sunshine hours. Under the condition of K application, the whole head rice rate decreased initially and increased with increasing effective accumulated temperature and sunshine hours during the growing period. However, it showed an opposite trend with the accumulated precipitation. The chalky grain rate decreased initially, and increasing with climate change, and the rate of change in gel consistency showed a decreasing trend with climate change.

Conclusions The application of nitrogen or potassium fertilizer synergistically increases fragrant rice yield and quality, which is more evident in indica fragrant rice. Similarly, accumulated precipitation, effective accumulated temperature, and sunshine hours affected the yield and quality traits of fragrant rice, ranging from 800–1100 mm, 2900–3400 ℃·d, and 800–1000 h, respectively. N fertilizer regulation can improve rice yield, milling quality, and cooking quality. When accumulated precipitation, effective accumulated temperature, and sunshine hours reach 500–800 mm, 2900–3400 ℃·d, and 400–600 h, respectively, K fertilizer regulation can improve rice yield, milling, cooking, and appearance quality.