The Effect Of Water And Nitrogen Coupling On Production Of Tomato In The Middle Reaches Of Heihe River

Water and nutrient are two key factors affecting crop growth and development,and their effects are interacted. Therefore, researches of the effects of fertilizers,water supplement and their coupling effect on crop production have drawn highattentions of the researchers worldwide.Water and nitrogen coupling indicates the phenomenon or the results due tointeractions of soil water and nitrogen in agro-ecosystem. The coupling effect ofwater and nitrogen emphasizes and takes the advantages of the integral effects toincrease the output of the crop and the utilization efficiency of water and fertilizer.This experiment was conducted in Linze experiment station of environment andengineering institute of cold and arid regions of CAS in2012. Tomato (Lycopersiconesculentum) cv. Hegel87-5was used as the material. Three soil water gradients(fullirrigation-W1, light deficit irrigation-W2and medium water deficit irrigation-W3)and three nitrogen levels(low nitrogen, N1; moderate nitrogen, N2and high nitrogen,N3)were adopted in two-factor randomized block design to study the effects of soilwater, nitrogen and their coupling effect on plant growth, accumulation of dry matter,the output and the quality of tomato fruits as well as the water use efficiency andeffectiveness of irrigation water so as to provide theoretical basis for the high quality,output and effective production of the crop. The main results are:1. Water deficit and low nitrogen caused weakened plant growth and decreasedfruit yield of tomato. Plant heights, stem diameters, leaf numbers, flower and fruitnumbers all decreased with low soil moisture and nitrogen levels. But significantcoupling effect between water and nitrogen was observed on branching of thetomato plants.Under the same soil moisture, moderate nitrogen fertilization caneffectively improve tomato production, while high nitrogen supplement resulted inyield reduction of tomato.2. Combinations of middle or high water and nitrogen levels can significantlyincrease dry matter accumulation of tomato. Under high soil water condition, plant dry matter accumulation can increase by11.73%to12.31%and by15.77%to12.29%under high nitrogen levels. The coupling of water and nitrogen also hadpositive interactions on plant reproductive allocation of tomato.3. Moderate water deficit combined with high nitrogen supplement had thehighest water use efficiency (0.1624kg/m~3) and fruit productive efficiency (55.50kg/m~3) of irrigation water, but no significant differences from moderate water andnitrogen treatment was found.4. Increasing soil moisture showed negative impact on fruit quality of tomato,and the effect can be discounted by nitrogen fertilizing. Under the same soilmoisture, the ratio between solid substances and acids of tomato fruit can reducesignificantly d (from22.69%to17.05%) when nitrogen level was increased. Underthe same nitrogen level, the total acidity of the tomato fruit increased with theincreasing water deficit. Water deficit and nitrogen supplement can improvelycopene content but not ascorbic acid content of tomato fruits.Overall, the suitable soil moisture and nitrogen level for tomato production in theregion are55%～65%(moderate deficit) and purity nitrogen172.5kg/hm~2(middlelevel) respectively.