Abstract:

The aim is to investigate the effects of reducing and postponing base fertilizer supply on nutrient absorption and root growth of summer maize under drip irrgation. ‘Zhengdan 958’ was used as the test material, three treatments were set up, i.e. traditional base fertilizer supply (CK), postponing base fertilizer supply to V6 (T1) or V12 (T2), the dry matter accumulation, root growth, plant nitrogen nutrient index, nutrient accumulation, soil nitrate nitrogen content and yield of summer maize were investigated. The results showed that although the nitrogen nutrition index of T1 and T2 was lower than 1 (0.88) at jointing stage (V6), the difference in contents of N, P, K and dry matter accumulation of shoot among the treatments was not significant, and for T2, the plant nitrogen accumulation from silking stage (R1) to mature stage (R6) was higher than that of the CK (+33.39%). There was significant difference among the three treatments in nitrate nitrogen content in 0-20 cm soil layer between rows, while the value of T2 was 41.85% and 35.46% lower than those of CK and T1, respectively. The content of nitrate nitrogen in 80-100cm soil layer of T1 and T2 treatments was lower than that of CK by 78.68% and 56.02%, respectively, the difference was not significant. The root surface area density of 15-30 cm soil layer was T2 > T1 > CK in the bell-mouthing stage (V12), in which T2 and T1 was 25.89% and 36.17% higher than CK, respectively, and the root surface area density of 30-45 cm soil layer in T2 treatment was 68.59% higher than CK. Overall, the harvest index and yield of T2 treatment were relatively the highest, the difference was not significant, and the nitrogen utilization rate of T2 was 12.13% higher than that of CK. Therefore, under drip irrigation, the ratio of base fertilizer and topdressing should be optimized according to the soil fertility in summer maize production. The base fertilizer in middle and high fertility farmland could be appropriately reduced and topdressed to V6 or even V12, to control the growth at early stage and keep sufficient fertilizer for later growth, reduce the residual nitrate nitrogen in the soil and promote the root growth.

Key words: summer maize, reducing and postponing of base fertilizers, nitrogen use efficiency, nitrogen nutrition index, soil nitrate nitrogen residue