Abstract
The efficient use of water and fertilizer is vital for optimizing plant growth and yield in rice production. To achieve sustainable rice production and resource management, the ways in which applied water and nitrogen affect the root and shoot morpho-physiology, as well as yield, must be understood. In this study, a pot experiment was conducted to investigate the effects of slow-release nitrogen fertilizer (sulfur-coated urea) application at three levels (light nitrogen (NL), medium nitrogen (NM), and heavy nitrogen (NH)) on the growth, yield, and nitrogen use efficiency (NUE) of rice grown under three water regimes (wetting and soil saturation (WSS), wetting and moderate drying (WMD) and wetting and severe drying (WSD)). The results revealed that differences in water regimes and fertilizer rates led to significant differences in the roots, shoots, yield, and NUE of rice. Increasing the N dosage by 5% enhanced the root and biomass production by 16% in comparison with that of the other groups. The NH×WSS treatment produced the greatest root length, weight, density, active absorption, and oxidation. However, the integration of WSS × NL generated the maximum value of nitrogen apparent recovery efficiency (63.1% to 67.6%) and the greatest value of nitrogen partial factor productivity (39.9 g g−1 to 41.13 g g−1). Transmission electron microscopy (TEM) images showed that plants grown under high and medium nitrogen fertilizer rates with WSS had improved leaf mesophyll structure with normal starch grains, clear cell walls, and well-developed chloroplasts with tidy and well-arranged thylakoids. These results show that TEM images are useful for characterizing the nitrogen and water status of leaves in the sub-micrometer range and providing specific information regarding the leaf microstructure. The findings of this study suggest that the application of NH×WSS can produce improvements in growth traits and increase rice yield; however, the NL×WSS treatment led to greater NUE, and the authors recommend its usage in rice agriculture.
Highlights
In the 21st century, agriculture faces the challenge of producing enough food to feed the world’s rapidly expanding population under conditions of increasing water scarcity.Rice is one of the most popular staple food crops worldwide, feeding over 40% of the global population and 60% of the Chinese population [1]
This study revealed that the root total surface area was increased significantly under the wetting and soil saturation (WSS) × NH treatment compared to the WSS ×N0, WSS × NL, and WSS × NM treatments, because the WSS × NH treatment increased the available N during rice growth
The findings of the present study revealed that morphological characteristics of rice roots, such as root weight density (RWD), root length density (RLD), total surface area (TSA), and RDW, affect N
Summary
In the 21st century, agriculture faces the challenge of producing enough food to feed the world’s rapidly expanding population under conditions of increasing water scarcity. Rice is one of the most popular staple food crops worldwide, feeding over 40% of the global population and 60% of the Chinese population [1]. Several water-saving technologies have been implemented to optimize rice yield when water is scarce, including aerobic rice systems, drought-tolerant genotypes, and alternate wetting and soil drying (AWD) irrigation [4]. AWD methods were developed to reduce the amount of water utilized for irrigation in paddy fields by allowing them to dry out to soil field capacity before rewatering [5,6].
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