Effects of Nitrogen Rates on Yields and Quality of Watermelon, Cantaloupe and Honeyloup

A study was made of the response of six kinds of melons to different nitrogen fertilizer rates when grown with drip irrigation. Results indicated a general response of petiole nitrate and yields to increasing N rates, depending on the kind of melon. The study will be continued in 1990 and include water and N rates with three kinds of melons. MATERIALS AND METHODS Drip -irrigated field plots used for a melon study in 1988 were used in 1989. The field had remained fallow after the 1988 crop, and few weeds were present due to the dry winter. Beds were reshaped over the buried drip lines with a tractor -drawn blade and melons were seeded in dry soil with a Planet Jr. type planter on 15 March. Drip lines were reconnected to laterals, water meters and fertilizer injectors and the crop was irrigated daily as needed. The three N treatments were replicated three times and melons were planted in each row. Three N fertilizer levels were based on results of the previous year and weekly monitoring of petiole nitrates for each melon variety. The experimental irrigation system did not, however, allow for differences in N application rates to cantaloupe and watermelons. The schedule used for applying Solution 32 (urea -ammonium nitrate) is shown in Table 1 and final rates were 40, 100 and 170 kg N /ha. Zinc in the form of EDTA was applied to all plots on 1 June at a rate of 1.1 kg /ha. Total water applied was 600 mm. Melons used in 1989 were `Laguna' and `Topmark' cantaloupe, `Royal Sweet' and `Mirage' watermelon, and `Gallicum' and `11818' hybrid honeyloups. Each of the six melons was planted in 50 -ft. plots in each row. A satisfactory stand was obtained, except some reseeding of `Mirage' watermelon was required on 29 March. Thinning and weed control were done by hand. Petioles from youngest fully expanded leaves were collected on a weekly basis, beginning as early as 26 April for the more vigorous melons. Samples were dried and analyzed on a timely basis in order to use the data as a guide for N application. Melons were harvested twice a week, weighed and graded on an individual basis. Yields are shown in Table 2.