Salinity and Nitrogen Rate Effects on the Growth and Yield of Chile Pepper Plants

Salinity and low soil N availability are important growth limiting factors for most plants. Our objective was to determine the influence of different N fertilization rates and soil salinity levels on the growth and yield of chile pepper plants (Capsicum annuum L.) grown in a greenhouse in sandy loam soil for 2 yr. The targeted soil salinity levels were 1.3, 3.5, and 5.5 dS m^(-1) in 1999, and 1.3, 3.0, 4.5, and 6.0 dS m^(-1) in 2000 as electrical conductivity of the saturated paste extract (ECe). Total N application rates were 80, 140, and 200 kg ha^(-1) in 1999, and 30, 90, and 150 kg ha^(-1) in 2000. Nitrogen rates of 140 kg ha^(-1) or more increased soil salinities, in some cases by as much as 4 dS m^(-1). Soil salinity decreased plant relative growth rate (RGR) up to first mature pod stage. After this growth stage however, salinity increased the RGR. Low and medium N rates produced the maximum RGR up to the first mature pod stage. After this growth stage, the maximum RGR was achieved with the medium and the high N rates tested in 1999 and 2000, respectively. Increasing N rates and salinity levels interacted to reduce chile pod yield in 1999, and acted independently in 2000. This study indicates that over-fertilization during early plant development may contribute to salinity and decreased pod yield. While salt-stressed chile performs well when adequately fertilized, N should be applied in amounts that increase with plant need over the growing season.