Effects of soil fumigation and N source on soil inorganic N and tomato growth

Abstract

Soil fumigation, commonly used in vegetable production, may alter the rate of nitrification, affecting availability of N for crop use. The objective of this research was to examine effects of soil fumigation and N fertilizer source on tomato growth and soil NO3–N and NH4–N in field production. Experiments 1 and 2 included application of methyl bromide at 420 kg ha-1 to a Norfolk sandy loam (fine loamy siliceous thermic Typic Kandiudult) in combination with preplant applications of calcium nitrate, ammonium nitrate, and ammonium sulfate at 144 kg N ha-1. An additional fumigant, metam-sodium, was included in the second experiment at 703 L ha-1 (268 kg sodium methyldithiocarbamate ha-1). Experiment 3 included methyl bromide and metam-sodium, with ammonium sulfate as the sole source of N applied at 144 kg N ha-1. In the first two studies, fumigants had little or no effect on soil NH4–N or NO3–N concentration. Tomato plants were larger and fruit yield was greater in fumigated plots, but there were few growth or yield responses to N source. In the third experiment, fumigants increased concentration of soil NO3–N and NH4–N at 16 days after fumigation (DAF), however, there was no effect on nitrification owing to fumigants. It appears that N source selection to overcome inhibition of nitrification is not necessary in plant production systems that involve fumigation