Nitrogen forms affect root growth, photosynthesis, and yield of tomato under alternate partial root-zone irrigation

摘要

To increase efficiency of water and nitrogen (N) fertilizer use, this study was conducted with a split-root pot experiment to investigate the effects of different forms of N fertilizer on root growth, photosynthesis, instantaneous water use efficiency (IWUE), and yield of tomato (Lycopersicon esculentum L.) under alternate partial root-zone irrigation (APRI). Three irrigation modes comprised conventional irrigation (CI) and two kinds of APRI, i. e., APRI with water content in the drying soil compartment controlled at >= 60% or 40% of the water-holding capacity (APRI-60, APRI-40). Two N forms included ammonium-N and nitrate-N supplied as calcium nitrate or ammonium sulfate, respectively. The results show that APRI-60 enhanced root growth and increased leaf IWUE with a slight yield reduction compared with CI regardless of the N form supplied. In contrast, APRI-40 significantly decreased root growth and inhibited photosynthesis, thereby resulting in a significant yield loss. In addition, at the flowering stage tomato plants grew better with ammonium-N than nitrate-N supply; however, at the fruit expansion stage and maturity stage, the tomato plants had a higher biomass accumulation and yield with nitrate-N than ammonium-N supply. Therefore, the application of APRI should consider the soil water condition coupled with an appropriate N form. In the present study, APRI controlled at >= 60% of the water-holding capacity (WHC) for the drying soil side with nitrate-N supply was the best water-fertilizer supply for tomato cultivation.