Abstract
In the middle and lower reaches of the Yangtze River, the rainfall is greater in summer. The technology of rain catching and controlled irrigation of rice help to save water by raising the water depth of the field after rain while the soil water content during the rest period is maintained at 70–100% of field capacity. The objectives of this study were to evaluate rice growth, canopy light utilization, and yield of rice under different rain-catching and controlled irrigation modes (T1: light drought and low storage, T2: light drought and high storage), and to find the optimal storage depth after rain for rice. Measurements included the rice plant height, tiller number, high tiller growth, leaf angle, canopy interception rate, and yield shape. The plot experiment was conducted in 2012 and 2013 using Nanjing 44 (Oryza sativa L.) as the test material. The results showed that T1 treatment improved the height of rice plants and the number of effective tillers in the late growth stage. The number of high tillers had a great influence on the total leaf dry quality; compared with conventional irrigation (CK), the number of high tillers increased by 11.36% and 7.87% in T1 and T2, respectively; the canopy interception rate of T1 above 0 cm was higher than that in T2 and CK; and the leaf area index (LAI) was closely related to the 0–40 cm of canopy light distribution. The number of grains per panicle in T1 was lower than in CK and T2; however, the number of grains in T1 was less, and the 1000 grain weight was higher. On the 63 days and 83 days after transplanting in 2012 and 78 days after transplanting in 2013, the first, second, and third leaf angles of T1 were larger. Rain-catching and controlled irrigation can increase the dry weight and shoot dry weight of rice, and light drought and low storage (T1) conditions are good for maintaining a high yield because of more tiller number, more grains per panicle and reasonable light distribution.
Highlights
The photosynthetic potential productivity of rice mainly depends on two factors: the interception of photosynthetically active radiation and the conversion efficiency of photosynthetically available radiation energy
The interception rate of photosynthetically active radiation are different in different growth stages of rice [8]
The leaf area index (LAI) was shown to be closely related to a 0–40 cm canopy, especially below 20 cm
Summary
The photosynthetic potential productivity of rice mainly depends on two factors: the interception of photosynthetically active radiation and the conversion efficiency of photosynthetically available radiation energy. Leaf morphology (such as leaf thickness, specific leaf area, and so forth) regulates plant absorptivity by changing the optical path [2]. Plants change their leaf morphology according to the surrounding light environment, Water 2018, 10, 1340; doi:10.3390/w10101340 www.mdpi.com/journal/water. Active radiation (PAR) in rice fields can be divided into three parts: penetration, reflection, and absorption. The leaf area index (LAI) affects the PAR interception of the canopy by affecting these three parts [7]. The interception rate of photosynthetically active radiation are different in different growth stages of rice [8]. The leaf angle distribution is closely related to the canopy light distribution, and the leaf angle is the main factor determining the LAI distribution
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