Abstract: A 3-year field experiment was conducted in a dryland area on the Loess Plateau, eastern Gansu Province, China, to study the effects of straw incorporation and nitrogen fertilizer reduction on the yield, water use efficiency (WUE), and physiological traits of spring maize (Zea mays). The six treatments included normal fertilization with nitrogen fertilizer at 225 kg N·ha^-1 (F), total straw incorporation of 9000 kg dry matter·ha^-1 (TS), F+TS, 80% F+TS, 60% F+TS, and no fertilization or straw incorporation (control, CK). Compared with the F+TS treatment, both the 80% F+TS and 60% F+TS treatments increased the yield and WUE of spring maize. However, the differences in the grain yield and WUE were not significant among the F+TS, 80% F+TS, and 60% F+TS treatments. The treatments could be ranked, from highest 3-year average yield and WUE to lowest, as follows: 80% F+TS>60% F+TS>F+TS>F>TS>CK. Compared with the F+TS treatment, the 80% F+TS treatment increased yield by 9.9% and the WUE by 8.2%. Compared with CK, the 80% F+TS treatment increased yield by 46.9% and increased the WUE by 52.4%. Compared with the F+TS treatment, the 60% F+TS treatment increased yield by 2.6% and increased the WUE by 37.2%. Compared with CK, the 60% F+TS treatment increased yield by 3.7% and increased the WUE by 46.1%. Compared with all other treatments, the 80% F+TS and 60% F+TS treatments increased soil and plant analyzer development (SPAD) values and dry matter accumulation during the whole growth period of spring maize. The results of this study suggest that 60%-80% F+TS treatments are the optimal fertilization methods for spring maize crops cultivated in dryland areas on the Loess Plateau in eastern Gansu Province, China.

Key words: straw returning, nitrogen reduction, dryland spring maize, yield, physiological indicator