ROW SPACING EFFECT ON SOIL AND LEAF WATER STATUS OF SUMMER SOYBEAN

The effects of row spacing (RS) on soil water content (SWC), leaf relative water content (RWC), leaf water potential (Psi), and osmotic potential (pi) were investigated in summer soybean crops in Northern China during the 2007 and 2008 growing seasons. The experiment consisted of five planting patterns resulting in the same plant population density (3.09 x 10(5) plant.ha(-1)), with RS of 18, 27, 36, 45, and 54 cm. A significant negative correlation was observed between RS and SWC, RWC, Psi, pi, Y in both years (P < 0.05). SWC, RWC, Psi, and pi correlated positively with Y in soybean. The daily rainfall caused fluctuations in SWC. In 2007 and 2008, the mean values of RWCs, Psi, and pi for RS 18 and 27 were significantly higher than that of RS 54 (P < 0.05). At the grain-filling stage, the hourly Psi of the different RS treatments produced a V-shaped curve trend in one day, and the minimum of the curve appeared in midday. These results indicated that this was a beneficial response for yield under the high SWC, RWC, Psi, and pi conditions. Therefore, narrow RS improved soil and leaf water status and could increase yield of crops.