Carrot Yield, Quality, and Storability in Relation to Preplant and Residual Nitrogen on Mineral and Organic Soils

Abstract

<jats:p>The Nutrient Management Act (NMA) established in the province of Ontario in 2002 has prompted a re-evaluation of nitrogen (N) management practices. However, N management research in Ontario is currently outdated. The experiment in this 3-year study was designed to establish the yield response of carrot (<jats:italic>Daucus carota</jats:italic>) to N fertilization on mineral and organic soils and identify the relative yield effects of preplant and residual soil N. In 2002, N was applied at 0%, 50%, 100%, 150%, and 200% of recommended N application rates in Ontario as ammonium nitrate (organic soil: 60 kg·ha<jats:sup>-1</jats:sup> preplant; mineral soil: 110 kg·ha<jats:sup>-1</jats:sup> split 66% preplant/33% sidedress). Experimental units were split in half in 2003 and 2004, and N was applied to one half in 2003 and both halves in 2004 to identify the effects of residual N from the previous season on yield. Crop stand, yield, and quality were assessed at harvest, and storability was assessed by placing carrots into cold storage for 6 months. Nitrogen application rate had no effect on the yield, quality, or storability of carrots grown on organic soil. On mineral soil there were no effects of applied N in the first year of the 3-year study. In the second and third year on mineral soil, yield increased in response to increasing N, up to 200% and 91% of the recommended application rate, respectively, based on the regression equations. Yield declined above 91% of the recommended application rate in the third year due to a decrease in stand at higher N application rates. There were no effects of N on carrot quality or storability on mineral soil. On mineral soil, residual N from the 2002 season had more effect on yield at harvest in 2003 than N applied in 2003. This major effect of residual soil N on yield provides an explanation for the lack of yield response to preplant N application in previous studies conducted in temperate regions. These results indicate that there is no single N recommendation that is appropriate for all years on mineral soil. Assessing the availability of N from the soil at different depths at seeding is recommended to determine the need for N application.</jats:p>

Establishment of Critical Sap and Soil Nitrate Concentrations using a Cardy Nitrate Meter for Two Carrot Cultivars Grown on Organic and Mineral Soil

“…The most consistent critical sap NO 3 -N concentrations occurred at the late sampling date for both soil types and both cultivars. The critical levels reported for organic soil can only be assumed to be maximum critical concentrations because optimal yield may have been achieved under lower N fertility levels than occurred in the no-N treatment in all three years (Westerveld, McDonald, and McKeown 2006). "Idaho" had consistently lower critical sap NO 3 -N concentrations than "Fontana", especially at the first two sampling dates (Table 4).…”

“…It is possible that crop growth was limited by Westerveld, McDonald, and McKeown (2006) and calculated from regression equations for each cultivar where significant, assuming no N rate is desired rate where no effect of N on total yield exists. Recommended rates: organic soil ¼ 60 kg .…”

“…Yield samples were collected from these plots, and results were as described in Westerveld, McDonald, and McKeown (2006). There was no yield response in any of the 3 years on organic soil or the first year on mineral soil.…”

“…However, when soil residual N is low, which occurs mainly on sandy soils, carrot yield can increase up to an N application rate of 220 kg . ha 21 (Westerveld, McDonald, and McKeown 2006). In addition, carrot yields respond to N in most studies conducted in tropical or subtropical regions (Arora and Mathur 1972;Burdine and Hall 1976;Hipp 1978;Hochmuth, Brecht, and Bassett 1999), which is probably due to increased rainfall in these regions during the winter growing season (Hochmuth, Brecht, and Bassett 1999).…”

“…Generally, carrots grown in temperate regions do not respond to applied N (Hamilton and Bernier 1975;Warncke 1996;Sanderson and Ivany 1997;Westerveld 2002;Westerveld et al 2006). However, when soil residual N is low, which occurs mainly on sandy soils, carrot yield can increase up to an N application rate of 220 kg .…”