Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 5, 2006
Publication Date: February 1, 2007
Citation: Alva, A.K. Petiole and soil nitrogen concentrations during the growing season of two potato cultivars as influenced by different nitrogen management practices. Commun. Soil Sci. Plant Anal. 38, 403-421. 2007. Interpretive Summary: Poor management of nitrogen (N) fertilizers can result in excess leaching of nitrate (NO3-) below the crop rootzone resulting in contamination of groundwater. Combination of crop monitoring for nutrient status and soil monitoring for transport of nitrate is useful to minimize nitrate leaching losses. This paper reports two years' data on petiole nutrient monitoring and soil nitrogen forms monitoring under different N management practices for Ranger Russet and Umatilla Russet potato varieties grown on a sandy soil in the Pacific Northwest. The petiole nitrate evaluations showed both years the concentrations in the optimum or excess range about 40 to 60 days following the pre-plant N application. During the subsequent growth period, the petiole N levels were in the low range. The soil N (both ammonium and nitrate forms) in the top 4 feet soil returned to the background concentrations within about 100 days after application of pre-plant N regardless of the N rates. The in-season N applications had minimal impact on the soil N levels. Therefore, application of N as fertigation with irrigation water is preferred method to minimize leaching losses.
Technical Abstract: Finetuning nitrogen (N) management for crop production in sandy soils, under irrigated production, is a desirable goal to optimize production and minimize negative impacts on the environment. Monitoring the crop for adequate nutrient status and soil analysis for residual soil N are important to evaluate the effects of different N management practices on N uptake efficiency as well as potential for leaching losses. Effects of different rates of pre-plant N application and different rates and frequencies of in-season N on the petiole nutrient status, as well as changes in soil N status (120 cm depth) were evaluated for 'Ranger Russet' and 'Umatilla Russet' potato cultivars grown on a Quincy fine sand (mixed, mesic, Xeric Torripsamments) in the Pacific Northwest (PNW). In the 2001 experiment, the petiole NO3-N concentrations in both the cultivars were either in the optimum or excess range until about 30 days after application (DAA) of pre-plant N (PP-N), followed by in the low range until about 40-45 DAA of PP-N. In the subsequent sampling, the petiole NO3-N concentrations showed a wide range proportional to the rates of in-season N (IS-N). In the 2002 experiment, the petiole NO3-N concentrations were in the excess range until about 55 to 60 DAA of PP-N in both the cultivars, followed by a decline in concentrations to the low range. The petiole P and K concentrations were mostly above the excess range in both the cultivars over the entire sampling period. The soil N data showed that the transformation of urea N was quite rapid and that the extractable NH4-N and NO3-N concentrations in the soil returned to the background levels within 100 days after the pre-plant N application. By this time period, the soil profile N status was independent of preplant N rates applied.