Nitrogen and Phosphorus Needs for Tomatoes and Green Peppers Grown with Drip Irrigation
IPNI-2002-CAN-ON27
05 May 2003
Methodology
- The experiments were conducted in a Granby sandy loam soil at the GPCRC, Harrow, ON. For processing tomatoes, treatments included 4 fertilizer N rate ranging from 0 to 258 kg N ha-1 and 3 fertilizer P rates ranging from 0 to 200 kg P2O5 ha-1. For green peppers, treatments included 4 fertilizer N rate ranging from 0 to 198 kg N ha-1 and 3 fertilizer P rates ranging from 0 to 200 kg P2O5 ha-1. For both crops, the plots were arranged in a factorial randomized completely block design, with 4 replicates for a total 96 plots. All fertilizer P and about 40% of fertilizer N were pre-transplant broadcasted and the remaining fertilizer N drip-fertigated. Drip fertigation was applied to all plots using the existing computerized Fertigation Manger system at GPCRC. Weeds were controlled with Treflan + Dual Magnum + Sencor pre-plant incorporation. All other plot managements followed the local practices.
For processing tomatoes, fruits from the central rows of each plot were harvested at the 80% fruit ripening (or peak ripening) stage and graded into processing ripe (marketable), green and cull, and weight recorded. Total fruit yield was calculated. Fruit soluble solids were measured. Fruit and stover were sampled and to be analysed for N and P contents. Total N and P uptake and removals will be calculated in combination with fruit and stover yields.
Leaf petiole nitrate (NO3-N) and potassium measurements were conducted using Cardy nitrate and potassium metre (Spectrum Technologies, Plainfield, IL). Thirty-five leaf petiole samples from the 4th leaf of the complete growing tip were taken from each plots once in a week. The petiole samples were put in a plastic bag and stored in a cooler immediately. At the same day, the composite juice from each plot was analysed for NO3-N and K in the laboratory.
For green peppers, fruits were harvested once a week (7 times of harvests during the season). Fruit were ranked as marketable and non-marketable yields. Fruit and stover were sampled and analysed for moisture, nitrogen and phosphorus contents. Total nitrogen and phosphorus uptake and removals were calculated in combination with fruit and stover yields. Nitrogen and phosphorus requirements for each ton production of green peppers were calculated.
Soil profile samples (0-20, 20-40, 40-60, 60-80, and 80-100 cm depths) were taken before planting and shortly after harvesting and analysed for NO3-N and NH4-N to evaluate the leaching potential of soil N as a function of fertiliser rates. Because of the very low contents of soil NH4-N, the results were not included in the report.
Impacts of fertilizer nitrogen and phosphorus on yield, quality, nitrogen and phosphorus uptake and removal, and potential losses of soil N and P were analysed and quantified using the SAS program.