Optimizing Levels of Water and Nitrogen Applied through Drip Irrigation for Yield, Quality, and Water Productivity of Processing Tomato (Lycopersicon esculentum Mill.)

Abstract

The main goal of this study was to evaluate the effects of different levels of irrigation water and nitrogen on yield, quality, and water productivity of processing tomato grown in clay-loam soil. Three water levels of pan evaporation ($E_{pan}$) replenishment applied via drip irrigation ($1.00{\times}E_{pan}$, $0.75{\times}E_{pan}$, and $0.50{\times}E_{pan}$) and four N application rates with fertigation (0, 60, 120, and $180kgN{\cdot}ha^{-1}$) were tested in the sub-humid climate conditions of Turkey during the 2010 and 2011 growing seasons. The highest marketable yields were observed with full irrigation ($1.00{\times}E_{pan}$) for each season. Decreasing irrigation rate generally improved dry matter, total soluble solids, total sugars, titratable acidity, lycopene and total carotene, and decreased fruit $NO_3$-N content and fruit total protein content slightly. The highest water productivity was obtained with a moderate soil water deficit ($0.75{\times}E_{pan}$). The $180kgN{\cdot}ha^{-1}$ fertilization rate produced the highest values for marketable yield, fruit size, total soluble solids yield, $NO_3$-N, and total protein content. Increasing N rate also increased the values of fruit total sugars and titratable acidity. Increasing both irrigation and N levels increased the $NO_3$-N and protein contents. The higher lycopene and total carotene values were obtained in the treatments of 60 and $120kgN{\cdot}ha^{-1}$. Increasing N supply improved the water productivity with the 3 irrigation application ratios. Considering the quantity and quality for the processing and water productivity, the $0.75{\times}E_{pan}$ irrigation regime and a 120 or $120kg{\cdot}ha^{-1}$ nitrogen supply can considered optimal.

Keywords

• carotenoids;
• limited irrigation;
• N fertilization;
• total soluble solids;
• water-use efficiency