Abstract
The critical nitrogen dilution curve (CNDC) can be used as a diagnostic tool to assess crop N nutrition during the growing season. Potato cultivars have different biomass production and accumulation of N and consequently different growth patterns. These differences among cultivars may result in different CNDC. The aims were a) to determine the CNDC for different potato cultivars; b) to compare these curves with reference curves; and c) to assess the possibility of using the CNDC to estimate the N nutritional status of the crop. The biomass production and N concentration of shoots and tubers of potato cultivars Innovator, Gem Russet, Umatilla Russet, Bannock Russet and Markies Russet were measured. The harvest index (HI) and N harvest index (NHI) were determined. The coefficient a of the CNDC was similar among cultivars, while the coefficients b for Innovator and Gem Russet (-0.42 and -0.36, respectively) were smaller than those for the other cultivars (average -0.25). HI and NHI were greater in Innovator, smaller in Markies Russet, and intermediated in the other three cultivars. The coefficients b of the CNDC were correlated with HI and NHI (HI, r = -0.62, p < 0.0001 and -0.53, p < 0.0001; NHI, r = -0.60, p < 0.0001 and -0.61, p < 0.0001 for 2004/5 and 2005/6, respectively). The relationship between relative tuber yield (RY) and N nutrition index (NNI) was fit by a quadratic-plateau function. At similar situations of N deficiency, Innovator had lower yield and greater response to N rate than the other potato cultivars. The differences in HI and NHI among cultivars may explain the differences in the coefficient b of the CNDC. The NNI identified the status of N adequately in potato cultivars.
Highlights
Potato (Solanum tuberosum L.) crop frequently requires great application rates of nitrogen (N) fertilizer to achieve high tuber yield and quality
Nitrogen concentration decreased as total biomass increased in all of the studied cultivars (Figure 1), coinciding with the results determined by Lemaire and Gastal [7]
This decline in N concentration with time, or increasing biomass, is attributed to a decrease in the fraction of total plant N associated with photosynthesis in relation to a concomitant increase in the N fraction of structural and storage constituents [7]
Summary
Potato (Solanum tuberosum L.) crop frequently requires great application rates of nitrogen (N) fertilizer to achieve high tuber yield and quality. An adequate determination of the N fertilizer rate to be applied is important from both economic and environmental points of view [1] [2]. The optimal N fertilizer rate can vary widely among sites and among years. This variation results from the variation in both the N demand and the soil N supply. The development of tools to precisely predict the N requirement can optimize tuber yield and quality, while minimizing the risk of N losses to the environment [1] [4]
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