Yield, quality and nitrogen use efficiency of fertigated watermelon

Trials on a watermelon crop were carried out in 2000, 2002 and 2003 in a sub-humid area on fertile soils (Po Valley, Italy). The crop was plastic mulched and protected by a small tunnel during the early growth stage. The experimental design consisted of split plots with 4 replications: a Not Irrigated-Not Fertilised Control (NINF); a Irrigated-Not Fertilised Control (INF), and both '' Static '' and '' Dynamic '' fertigation. Static and Dynamic fertigation increased commercial yield by 33.7% and 57.7% respectively compared with the NINF treatment. The INF control increased the 1st class yield by 5.8%. There were no differences in 2nd class yield, waste yield and soluble solids in the fruit between treatments. Fruit K and Mg contents were not affected by fertigation, whereas Ca content increased by about ten times. Relative to NINF, the gross margin of the INF treatment increased by 6.6%, and the profit from the Static and Dynamic treatments were greater by 2798 and 4674 Euro ha(-1) y(-1) respectively. Dry matter accumulation and partitioning and root zone volume algorithms were developed.