Effect of spatio-temporal deficit irrigation and nitrogen supply on water and nitrogen use of tomato
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Abstract
For sustainable water use in protected agriculture, crop-specific and water-saving irrigation techniques that do not negatively affect crop productivity must be developed. Globally, successful attempts have been documented regarding the use of deficit irrigation methods. Regulated deficit irrigation (RDI) and controlled alternate partial root-zone irrigation (CRAI) have been used to improve irrigation water use efficiency (IWUE) of various crops. Because nitrogen (N) has been the most widely used fertilizer, N demand was likely to grow in the future. Thus the optimization of water and fertilizer use in vegetable production was a critical water/fertilizer-saving strategy. Four irrigation treatments under CRAI and three N levels were explored for optimum modes of water and fertilizer supply in vegetable production under water-saving irrigation in a pot tomato experiment. The irrigation treatments were WHWH (high water level through out growth period), WHWL (high water level at flowering and fruit-setting stages with low water level at full-fruit stage), WLWH (low water level at flowering and fruit-setting stages with high water level at full-fruit stage) and WLWL (low water level through out growth period). Then the N levels included NH high N, 0.45 g(N)·kg-1, NM medium N, 0.30 g(N)·kg-1 and NL low N, 0.15 g(N)·kg-1. Using conventional irrigation (CI) as control experiment, the effect of spatio-temporal of deficit controlled deficit irrigation (STCDI), which combined RDI and CRAI, and N rates on the vegetative parts of tomato dry matter accumulation (DMA), irrigation water use efficiency (IWUE), N accumulation (NA) and soil water and mineral N distribution were studied. Compared with CI, the results showed that WHWH, WLWH, WHWL and WLWL under CRAI decreased tomato DMA by 4.52%, 11.93%, 17.76% and 23.94%, respectively. They respectively decreased NA by 1.74%, 12.86%, 15.50% and 22.47%. The four irrigation treatments decreased N dry matter production efficiency (NDMPE) by 2.24%, 3.93%, 2.55% and 0.89% and increased IWUE by 12.39%, 8.99%, 15.02% and 12.96%, respectively. DMA, IWUE and NA of NA were highest under CRAI. Compared with NL, NM and NH decreased tomato NDMPE by 6.87% 12.70% and 17.81% 24.38% while increasing soil NO3--N content by 31.64% 159.58% and 57.37% 297.37%, respectively. High DMA, IWUE and NA were obtained under WHWH, CRAI and NM. The optimum mode for water and N supply under CRAI was 80% of CI irrigation (which was 70% 85% of soil field capacity) and nitrogen rate of 0.30 g(N)·kg-1(dry soil).
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