Reducing nitrogen fertilization of intensive kiwifruit orchards decreases nitrate accumulation in soil without compromising crop production

Excessive nitrogen （N） fertilization of high value horticultural crops is a common problem that not only increases the cost to farmers, but also negatively affects crop growth and the environment. A three-year field experiment was conducted in an intensive kiwifruit orchard in Shaanxi Province, China to compare the effects of reduced N fertilization applied as urea （U）, and controlled release urea （CRU） on the N nutrition of kiwi vines, fruit yield and quality, and nitrate-N accumulation in the soil profile. The three treatments included a conventional N application rate （CF-U, 900 kg N ha-1 yr-1 as urea）, two reduced N fertilization treatments where the amount of N fertilizer applied as U and CRU was reduced by 25％ in 2013 and 2014, and by 45％ in 2015. The 25 and 45％ reduced N treatments had no adverse effects on the N concentrations in leaves and pruning branches and the fruit yield and quality of kiwi vines. However, they significantly enhanced the partial factor productivity of applied N （PFPN） and the economic benefits, and reduced nitrate accumulation in the 0-200 cm soil profile. The same benefits of reduced N fertilization were observed for both the U and CRU treatments, but the CRU treatment had the added benefit of decreasing the loss of nitrate through leaching. We concluded that the current level of N fertilization in kiwi orchards is very excessive, and reducing the N fertilizer rate by 25-45％ could not only guarantee fruit yield, but also reduce N accumulation and loss.

Effects of biofertilizer and water-saving irrigation interactions on the leaf photosynthesis and plant growth of tomatoes

Irrigation and fertilizer interaction is an efficient cultivation management strategy for facility agriculture.However,the effects of irrigation and fertilizer management on tomato growth and its physiological factors remain unclarified.In this study,two irrigation patterns(W1,conventional irrigation;W2,water-saving irrigation)and four fertilizer application patterns(CF,chemical fertilizer;BOF,biological organic fertilizer;NPK,nutrient compound fertilizer;BOF+NPK)were selected to observe the effects of their interaction on cherry tomato plant growth,leaf photosynthesis and fruit quality through pot experiments.The results showed that W2 treatments promoted plant height growth compared to W1 under the same fertilizer addition.Moreover,irrigation and fertilizer management had significant effects on net photosynthetic rate,intercellular oxidation concentration,stomatal conductance and transpiration rate at the first sequence flowering and fruiting stages.The maximum tomato plant height(99.0 cm)was achieved under the irrigation and fertilizer pattern of BOF and W2,along with the highest fruit yield of 1.98 kg/plant,which was approximately 31.1%higher than the minimum yield under the combined CF and W2 treatment.Under W2 treatments,the application of either NPK or BOF increased the soluble sugar content of tomatoes.The structural equation models showed that the soil alkali hydrolyzed nitrogen could directly significantly affect the yield and soluble sugar.The findings suggest that optimization of irrigation-fertilizer interactions positively regulates tomato growth,providing an efficient model for tomato irrigation and fertilizer management and a reference for sustainable development of facility agriculture.