Inbred varieties outperformed hybrid rice varieties under dense planting with reducing nitrogen

Abstract

Field experiments were conducted over two years to evaluate the effects of planting density and nitrogen input rate on grain yield and nitrogen use efficiency (NUE) of inbred and hybrid rice varieties. A significant interaction effect was observed between nitrogen input and planting density on grain yield. Higher number of panicles per square meter and spikelets per panicle largely accounted for the observed advantage in performance of inbred, relative to hybrid varieties. Compared with high nitrogen input rate, nitrogen absorption efficiency, nitrogen recovery efficiency, and partial factor productivity increased by 24.6%, 28.0%, and 33.3% in inbred varieties, and by 32.2%, 29.3%, and 35.0% in hybrids under low nitrogen input, respectively. Inbred varieties showed higher nitrogen absorption efficiency, nitrogen recovery efficiency, and partial factor productivity than hybrids, regardless of nitrogen input level. Nitrogen correlated positively with panicle number, spikelets per panicle, biomass production at flowering, and after flowering in inbred varieties but only with panicle number and biomass production at flowering in hybrids. Inbred varieties are more suitable for high planting density at reduced nitrogen input regarding higher grain yield and NUE. These findings bear important implications for achieving high yield and high efficiency in nutrient uptake and utilization in modern rice-production systems. Rice (Oryza sativa L.) is the main staple food for more than half the population of the world 1. As one of the largest rice producers and consumers, China occupied 18.8% of the global rice-growing area and accounted for 28.1% of the total production in 2014 2. Double-season rice cropping has significantly contributed to the increase in rice productivity in China; however, the cultivated area has decreased substantially due to labor migration and increased labor costs over the past decades 3. Therefore, it is necessary to develop labor-saving cultivation technologies to reverse the declining trend in rice cultivation area in this country. Mechanical transplanting is an alternative labor-saving technology in rice production 4. As efficient agriculture has been popularized in recent years, mechanical transplanting has been rapidly adopted for rice production in China 5. However, rice farmers still follow traditional field management practices even under the mechanical-transplanting production scheme 6. Previous studies confirmed that certain traditional management practices, such as nitrogen (N) fertilization utilize resources inefficiently and have negative environmental impacts 7,8. In China, the average N application rate for rice production is 180 kg ha −1 , which is 75% higher than the global average 9-11. Consequently, only 20-30% of applied N is actually absorbed by the crop, while most of it is lost to the environment 6. Over the past three decades, this N-fertilizer overuse in China has caused surface water eutrophication, soil acidification, increased greenhouse gas emissions, and enhanced N deposit...

Grain Yield, Nitrogen Use Efficiency and Antioxidant Enzymes of Rice under Different Fertilizer N Inputs and Planting Density

“…High density reduced PFPn, which was similar to findings reported by Lu et al [38]. However, there were differences between our conclusions and those of that study, which may be because high planting density reduced rice yield (Table 2) and increased HIn, which was consistent with the conclusion of Xie et al [27].…”

Integrated Crop Management Practices Improve Grain Yield and Resource Use Efficiency of Super Hybrid Rice

“…Our results showed that the yield of OPT +N was clearly correlated with IPAR, IP, and RUE, with R 2 values of 0.88, 0.70, and 0.83, respectively. This study suggested that increasing IP at midtillering and IPAR at the grain filling stage significantly improved RUE ( Chen et al, 2019 ; Lu et al, 2020 ). These findings demonstrate that optimizing cultivation and nutrient management considerably increases the RUE of super hybrid rice and emphasizing appropriate practice is favorable to the environment.…”

Optimizing Planting Density and Impact of Panicle Types on Grain Yield and Microclimatic Response Index of Hybrid Rice (Oryza sativa L.)

“…However, previous studies have also found that increasing planting density can reduce weight per panicle and the total number of grains (Hayashi et al, 2006;Nakano et al, 2012). Lu et al (2020) believe that planting density only has a significant impact on effective panicle number, seed setting rate, and grain number per panicle.…”