Grain yield response to cultivar and harvest time of the first crop in rice ratooning in southwestern Japan

Abstract

Rice (Oryza sativa L.) ratooning has attracted attention due to its higher yield potential compared with conventional methods. Here, field experiments were conducted in southwestern Japan in 2019 and 2020 to determine the effects of cultivar (‘Takanari’, an indica cultivar, and ‘Koshihikari’, a japonica cultivar) and harvest time of the first crop (early and late) on the grain yields of the first and second crops in rice ratooning. For Koshihikari in 2019, grain yield of the second crop did not differ between harvest times. However, Takanari produced a lower grain yield at late harvest. Takanari had fewer spikelets, fewer filled spikelets, and a lower 1,000‐grain weight at late harvest. However, for Takanari in 2020, grain yield did not differ between harvest times. In 2019, the stubble nonstructural carbohydrate (NSC) content did not increase from early to late harvest, whereas the stubble leaf area index (LAI) decreased between harvest times; this difference was more apparent in Takanari than in Koshihikari. Contrastingly, in 2020, the NSC content increased from early to late harvest, but the stubble LAI did not differ between harvest times. Thus, the lower grain yield of late‐harvested Takanari in 2019 might be attributed to the lower stubble LAI resulting in fewer spikelets. In contrast, the maintained grain yield from early to late harvest in 2020 might be attributed to the maintenance of spikelet numbers via the higher stubble NSC content. Therefore, the sufficient stubble LAI and NSC could be essential for improving grain yield of the second crop.

Nonstructural carbohydrate content in the stubble per unit area regulates grain yield of the second crop in rice ratooning

“…NIL‐ GN1A Takanari had fewer panicles of the first crop but did not have a higher NSC concentration in the stubble. Recently, we examined the relationship between grain yield of the second crop and NSC content, NSC concentration, or leaf sheath plus stem weight for Koshihikari and an indica cultivar, Takanari (Tanaka et al., 2022). In a year when Koshihikari produced a higher grain yield of the second crop than Takanari, Koshihikari tended to have a higher NSC content due to the relatively higher NSC concentration.…”

“…The experiment was based on a split‐plot design with the main plot as rice genotype (NIL‐ GN1A Takanari and Koshihikari) and sub‐plot as cutting height of the first crop (high and low), arranged in a randomized complete block design with three replicates. Information of air temperature and solar radiation was reported by our previous studies (Nakano et al., 2021; Tanaka et al., 2022).…”

“…However, a recent study revealed that the initial regulator is the intense demand for sugars in the shoot apex (Mason et al., 2014). In rice ratooning, previous studies reported that grain yield of the second crop increased with increases in stubble nonstructural carbohydrate (NSC) concentration and/or content per area (He et al., 2019; Nakano et al., 2020, 2021; Tanaka et al., 2022; Tuner & Fund, 1993). However, the evidence was not sufficient to confirm the role of stubble NSC concentration and/or content per area on grain yield of the second crop.…”

Productivity and water use of ratoon rice cropping systems with water‐saving, drought‐resistant rice

“…Tanaka et al. (2022) also showed that low radiation capture reduced the effective panicles during the vegetative growth and the spikelets during the reproductive growth. Therefore, developing plants and cultivars with large panicles, by promoting the regenerative ability of the lower position nodes on the stubble of main‐season crops, may be crucial to the improvement of productivity in the ratoon season of WDR system.…”

“…He et al (2019) also found that the regenerative capacity was significantly positively correlated with the NSC content in the stubble of main-season crops in CLR. Higher DM accumulation in the stubble provides sufficient nutrients for the sprouting of axillary buds (Ichii & Sumi, 1983;Xu et al, 1997) and the differentiation of spikelets (Nakano et al, 2020(Nakano et al, , 2021Tanaka et al, 2022) in the ratoon season. Although the relationship between N content in the stubble of main-season crops and the regeneration capacity of ratoon season has not been reported, it is a common measure to apply N fertilizer at the 15th day after full heading of the main-season crop to promote the axillary bud sprout in the ratoon rice production (Ling et al, 1989;Wang et al, 2019).…”