Monday, 7 November 2005
4

Optimal Placement of Controlled Release Fertilizer for Seepage Irrigated Potato Production.

Fernando Munoz and Chad M. Hutchinson. University of Florida, PO Box 728, Hastings, FL 32145

Optimal placement of controlled release fertilizers (CRF, polymer coated urea) will reduce N application rates by increasing crop uptake efficiency and reduce the risk of nitrate leaching and/or runoff. Treatments were arranged in a factorial design consisting of three N-rates (112, 168, and 224 kg ha-1) and four fertilizer placements (banded 5 cm above-seed, banded 5 cm below-seed, mixed homogeneously throughout the row, and side-dressed at early emergence on row shoulders i.e. grower practice). Both the fertilizer placement and N-rate main effects were significant for NO3-N sap concentration at full flowering (FF). The interaction was not significant. Below-seed fertilizer placement treatment produced significantly higher NO3-N sap concentration at FF (1388 ppm) than mixed (968 ppm), above-seed (503 ppm), and sidedressed (258 ppm). CRF at 224 kg ha-1 produced the highest NO3-N sap concentration of all rates. Dry matter accumulation at FF was not affected by N-rate. However, fertilizer banded below-seed and mixed homogeneously in the row produced significantly higher dry biomass than above-seed and sidedressed treatments. There was a significant interaction between placement and rate for both total and marketable yield. Plants in the below-seed and mixed placement at the high N-rate, and below-seed placement at the medium N-rate produced the highest marketable and total yields averaging 33.8 and 37.2 MT ha-1 respectively. There were no significant differences between other treatments. Lowest marketable yields were observed for the above-seed placement at the high N-rate and the side-dressed treatment at the medium rate averaging 23.8 MT ha-1 and 17.9 MT ha-1, respectively. The side-dressed treatment produced a significantly higher percentage of tuber rots and incidence of tuber internal heat necrosis and a lower tuber specific gravity compared to all other treatments. Placement of CRF below-seed is a promising option to increase N uptake in potato under seepage irrigation.

Handout (.pdf format, 8668.0 kb)

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