[Coupling effects of periodic rewatering after drought stress and nitrogen fertilizer on growth and water and nitrogen productivity of Coffea arabica].

The effects of periodic rewatering after drought stress and nitrogen fertilizer on growth, yield, photosynthetic characteristics of leaves and water and nitrogen productivity of Coffea arabica (Katim P7963) were studied under different nitrogen application levels in 2.5 consecutive years. Irrigation (periodic rewatering after drought stress) and nitrogen were designed as two factors, with four modes of irrigation, namely, full irrigation (I: 100%ET+100%ET, ET was reference crop evapotranspiration), rewatering after light drought stress (I: 80%ET+100%ET), rewatering after moderate drought stress (I: 60%ET+100%ET) and rewatering after severe drought stress (I: 40%ET+100%ET), and three levels of nitrogen, namely, high nitrogen (N: 750 kg N·hm each time), middle nitrogen (N: 500 kg N·hm each time), low nitrogen (N: 250 kg N·hm each time), and nitrogen was equally applied for 4 times. The results showed that irrigation and nitrogen had significant effect on plant height, stem diameter, yield and water and nitrogen productivity of C. arabica, and plant height and stem diameter showed S-curve with the day ordinal number, and leaf photosynthesis decreased significantly under drought stress but most photosynthesis index recovered somewhat after rewatering. Compared with I, I increased dry bean yield by 6.9%, while I and I decreased dry bean yield by 15.2% and 38.5%, respectively; I and I increased water use efficiency by 18.8% and 6.0%, respectively, while I decreased water use efficiency by 12.1%; I increased nitrogen partial productivity by 6.1%, while I and I decreased nitrogen partial productivity by 14.0% and 36.0%, respectively. Compared with N, N increased dry bean yield and water use efficiency by 20.9% and 19.3%, while N decreased dry bean yield and water use efficiency by 42.4% and 41.9%, respectively; N and N increased nitrogen partial productivity by 81.4% and 72.9%, respectively. Compared with IN, IN increased dry bean yield, water use efficiency and nitrogen partial productivity by 37.6%, 52.9% and 106.4%, respectively. Regression analysis showed that the yield of dry bean was the maximum (2362 kg·hm) when the irrigation amount was 318 mm and the nitrogen application amount was 583 kg·hm; the water use efficiency was the maximum (0.78 kg·m) when the irrigationamount was 295 mm and the nitrogen application amount was 584 kg·hm, that's to say when yield of dry bean and water use efficiency reach the maximum value at the same time, the combination was the closest to IN. Therefore, the best combination of water and nitrogen model for C. arabica was IN.