Nitrogen Uptake Efficiency and Growth of Bell Pepper in Relation to Time of Exposure to Fertilizer Solution

Abstract

Irrigation of high‐value vegetable crops on sandy soils with poor water‐retention capacities may result in fertilizer nitrogen (N) displacement below the effective root zone prior to complete crop uptake. As a result, fertilizer N‐uptake efficiency (FUE) of vegetable crops is often relatively low, thereby increasing the potential risk of groundwater contamination. The objective of this study was to determine how time of exposure of the root zone to the N fertilizer (which is referred to as “fertilizer residence time” or t _R), as related to irrigation management, affects N uptake, FUE, growth, and yield of bell pepper (Capsicum annuum L.). Plants were grown in PVC columns with 45 kg of soil equipped with a drainage valve in the bottom of the column. Weekly irrigation with dissolved fertilizers (potassium nitrate; KNO₃) was applied 1, 3, or 7 d before weekly removal of residual soil N by leaching. Weekly N uptake rates were calculated by comparing total N recovery between unplanted (reference) and planted columns. At 77 d after planting, increasing the t _R from 1 to 3 or 7 d increased the weekly N uptake from 1.4 to 10.8 and/or 13.3 kg N ha⁻¹, respectively. Total calculated plant N accumulations were 19, 72, and 106 kg N ha⁻¹ for the 1‐, 3‐, and 7‐d t _R treatments, with overall FUE values being 8, 31, and 45%, respectively. It is concluded that during initial growth crop, uptake capacity is limiting, and more frequent (daily) fertilizer injection into the irrigation water may be required to enhance FUE. It is proposed also that via sound or innovative irrigation management practices, fertilizer retention in the root zone can be enhanced, thereby improving crop growth, yield, and FUE while reducing production cost and potential environmental impacts.

Keywords:

• Nitrate leaching
• nitrogen recovery
• pepper
• root system
• uptake dynamics
• vegetable crops
• yield

ACKNOWLEDGMENTS

Research was conducted with the financial support of the Florida Department of Agriculture and Consumer Services (FDACS) via the grant “Improved Use of Crop Nutrient Interception for Groundwater Protection.” We gratefully acknowledge Andrew Schreffler, Hannah Snyder, Huazhi Liu, Laura Avilla, and Kari Reno for their assistance with sampling and sample processing.