Effects of water supply in the upper and lower soil profiles of deep soil on root characteristics and dry matter production of winter wheat

Abstract

The purpose of this research was to test (1) the effect of supplying water in deep soil on wheat plant growth; (2) the modifying effect of root dry-matter allocation of wheat plants on shoot growth; and (3) the possibility of improving grain yield by using deep soil water. The experiment was conducted at the Northwest Institute of Soil and Water Conservation, Academia Sinica, and the Ministry of Water Conservancy, Yangling Shaanxi, P.R. China. Wheat plants were grown in 30-cm long, 7-cm wide, and 200-cm tall growth chambers which were divided into two layers at 1-m soil depth. The experiment included four treatments: (a) both soil layers were wet close to capacity (WW); (b) both layers were dry (DD); (c) the upper layer was wet and the lower layer was dry (WD); and (d) the lower layer was wet and upper soil was dry (DW). Soil water content in upper and lower layers after seven days of treatment measured 23.47% in WW, 15.01% and 13.90% in DD, 18.57% and 15.70 in WD, and 19.46% and 25.98% in DW. The experiment lasted for 68 days, in which period there was no additional water supply to the growth chambers. The experiment showed that DW treatment maintained the highest water content of both soil and plant, and produced a larger root system. In the DW lower soil level, root dry matter was the highest among the four treatments. Also, the dry weights of flat leaves and spikes were highest in the DW treatment. The results indicate that the DW treatment has the greatest yield potential. A soil water regime of dry upper soil and wet lower soil is beneficial for the initiation of root chemical signals and for a balance of water utilisation in the growth cycle. It promotes root development in deep soil and thus helps improve yield and water use efficiency.