Effects of Nitrogen and Water Rates on Nitrogen Uptake Dynamics in Drip Irrigated Sweet Corn

A complete factorial experiment using three nitrogen (67, 156 and 245 lbs N /acre) and three water rates (70, 100 and 130% consumptive use) examined the specific management criteria necessary for obtaining optimum yield and quality of dripirrigated `Sweetie '82' sweet corn. The crop was planted on 22 February and harvested on 30 May with an 86/50° F heat unit accumulation of 1444. When present, a nitrogen deficiency greatly decreased marketable yield number of marketable ears /plan4 mean ear weight, ear length and tip fill. Higher moisture rates generally had less effect on yield and quality than did N rates; however, increasing water rates significantly increased marketable yields and plant height. The effect of N and water rates on N and dry matter accumulation and on diagnostic plant tissue testing results for sweet corn are also presented The maximum marketable yield obtained in this experiment was 7.2 tonsper acre, using 245 lbs N /acre and 20.5 inches of irrigation water. INTRODUCTION Drip irrigation interests vegetable growers because it potentially can improve water and fertilizer use efficiency, as well as increase yields and quality. This research was begun in 1987 (Stroehlein, et al, 1988, Doerge et al, 1989) to obtain information on water use -efficiency and the nutrient requirements of sweet corn, as well as the cultural practices necessary for obtaining high yields and quality using subsurface drip irrigation. MATERIALS AND METHODS N and Water Effects on Yield and Quality `Sweetie '82' sweet corn was planted on 22 February 1989 on east west oriented 40 -inch beds, u.cing a commercial planter. This cultivar is an improved Super Sweet corn which produces 255% more sugar than normal sweet corns. It has 75% Sh2 and 25% SU + Sh2 genes. Drip tubing lines (Chapin Twin -wall IV) were buried 8 inches below the center of each bed, using a tractormounted, 2 -row injecting apparatus. The beds were relisted and smoothed with a commercial bed shaper to provide a flat, firm seedbed for more uniform seed placement and seedling emergence. A single seed row was planted on the south side of each bed to take advantage of solar radiation during the early season. The entire experimental area was treated uniformly until 28 March, when the corn was at the V3, or 3 -leaf stage of growth (Ritchie, et al, 1986). A total of 6.1 inches of water was applied during the establishment period. On 29 March, three nitrogen (N) and three water rates were imposed in a complete factorial design with four replications. The actual amounts of N and water applied throughout the season are listed in Tables 1 and 2. All N was applied through the drip system as liquid urea -ammonium nitrate (Solution 32). The three water rates (I, II and III) were intended to supply 70, 100 and 130% of the consumptive use of sweet corn respectively, based on historical data (Erie, et