Agronomic and physiological performance of high-yielding wheat and rice in the lower reaches of Yangtze River of China

Understanding agronomic and physiological performance of crop high yield is essential to make strategies for breeding and crop management. This study aimed to identify major agronomic and physiological traits associated with high grain yields of rice and wheat in the wheat–rice rotation system in the lower reaches of Yangtze River of China. Two high-yielding cultivars, each for winter wheat and rice, were field-grown from 2008 to 2010 for 3 years. Two crop management treatments, the local farmer's practice (LFP) and improved high-yielding cultivation (IHC), were used. The IHC adopted two new techniques, i.e., site-specific nitrogen management in both rice and wheat and alternate wetting and moderate drying irrigation in rice and controlled soil drying irrigation in wheat. Across the 3 years, the IHC yielded an average 9.67 t ha−1 of wheat and 12.55 t ha−1 of rice with an annual total of 22.2 t ha−1, an increase of 26.8% when compared with that (17.5 t ha−1) under the LFP. The increased grain yield under the IHC was mainly attributed to expanded sink size as a result of more kernels per spike or more spikelets per panicle, increased kernel weight of wheat and increased percentage of filled grains of rice. When compared with LFP, IHC showed a greater percentage of productive tillers, more pre-anthesis nonstructural carbohydrate (NSC) storage in the stem, greater leaf photosynthetic rate and concentration of cytokinins in root exudates, higher activities of sucrose synthase and adenosine diphosphoglucose pyrophosphorylase in grains, more dry mater production during the grain filling period, and higher harvest index. We conclude that (1) expanding sink capacity through an increase in kernels per spike or spikelets per panicle, (2) enhancing grain filling efficiency by an increase in pre-anthesis NSC in the stem, and (3) increasing post-anthesis dry mater production by an enhancement in root activity during grain filling should be considered as three major strategies for further increases in grain yields of wheat and rice in the lower reaches of Yangtze River of China.

► Under an improved high-yielding cultivation, an annual grain yield over 21 t ha−1 (>9 t ha−1 for wheat and >12 t ha−1 for rice) was obtained in a wheat–rice rotation system.
► The main agronomic and physiological traits of such a high yield were a large sink size, high filling efficiency, and great dry matter production during grain filling.
► An increase in pre-anthesis non-structural carbohydrate in the stem contributed to the high filling efficiency and a great root activity resulted in the great dry matter production during grain filling.
► An site-specific nitrogen management and an alternate wetting and moderate drying/or controlled soil drying irrigation are two key techniques in the high-yielding cultivation.