<i>Influence of water-nitrogen coupling on dry matter, yield and water use efficiency of flue-cured tobacco under mulch drip irrigation</i>

Abstract

Abstract. In order to explore the optimal water-nitrogen coupling modes of flue-cured tobacco under mulch drip irrigation, a drip irrigation experiment was carried out under the lysimeter. Three irrigation levels and three nitrogen levels were set and nine different water-nitrogen coupling treatments were carried out. effects of water-nitrogen coupling on accumulation and distribution of dry matter, yield and water use efficiency of flue-cured tobacco.The results showed that the accumulation of dry matter in different parts of flue-cured tobacco increased with the increase of irrigation amount, and increased with the increase of nitrogen application firstly, then decreased, excessive nitrogen application decreased the dry matter accumulation of flue-cured tobacco, the highest accumulation of dry matter was T8 with high water and middle nitrogen. The total dry matter did not changed obviously with the increase of root-shoot ratio. The proportion of leaf dry matter to total dry matter decreased with the increase of root-shoot ratio, and the decrease was more obvious. With the increase of root-shoot ratio, the proportion of dry matter distributed in the roots is constantly increasing, and the two of them showed a very significant linear positive correlation. The highest yield was T8 (500mm, 90kg/hm2) with the high water and middle nitrogen coupling, and the lowest yield of was T1 (300mm, 60kg/hm2) with the low water and low nitrogen. The highest water use efficiency was T2 (300mm, 60kg/hm2) with low water and middle nitrogen, and the lowest water use efficiency was T9 (500mm, 120kg/hm2) with high water and high nitrogen. The increase of nitrogen application is beneficial to increase the water use efficiency of flue-cured tobacco, while the water use efficiency is inversely proportional to the increase of irrigation amount, and increasing irrigation amount is not conducive to the improvement of water use efficiency. With regard to the accumulation and distribution of dry matter, yield and water use efficiency of flue-cured tobacco, 500 mm amount of irrigation combined with 90 kg/hm2 amount of nitrogen application rate is the best water-nitrogen coupling treatment. In the actual production of flue-cured tobacco, it should be balanced and coordinated the relationship between the yield, water use efficiency and water consumption, to meet the high yield conditions, to reduce the irrigation amount can reach a high yield and water saving coordinate unity.