| Popis: |
Data are presented from 3 field experiments that studied the effects of nitrogen (N) up to 360 kg N/ha, phosphorus (P) up to 100 kg P/ha, and potassium (K) up to 480 kg K/ha on tuber yield and the concentration of N, P, and K in petioles of youngest fully expanded leaves (P-YFEL) of potato cvv. Kennebec and Atlantic sampled when the length of the longest tubers was 10-15 mm. Data on the significance of relationships between total N and P, total N and nitrate-N, and chloride and nitrate-N in P-YFEL are also presented. At 1 site, Atlantic yielded 18% higher than Kennebec; at another, it yielded 21% less. Significant K x cv. and N x cv. interactions occurred at some sites. Increasing rates of applied N significantly increased total N concentrations in P-YFEL at all sites and nitrate-N concentrations at sites that were N-deficient. At 1 site, increasing the rate of applied P from nil to 100 kg P/ha significantly increased total N concentration from 2.8 to 3.4%. Total N concentrations in P-YFEL of Atlantic were significantly lower than Kennebec. For total N, there were significant N x K and P x cv. interactions. There was no significant interaction between N, P, and K in their effects on nitrate-N concentration in P-YFEL. At all sites, the application of N and P significantly increased P concentrations in P-YFEL, and mean concentrations were significantly greater in Kennebec than Atlantic. At sites deficient in K, the application of K significantly decreased P concentration. Significant N x cv. and P x cv. interactions occurred at 2 sites. At both K-deficient and non-responsive sites, increasing rates of applied K significantly increased K concentrations in P-YFEL. Differences between cultivars in K concentration were not significant at 2 sites, and although significant at the third, the difference (0.2%) was of little practical importance. At 2 sites, significant N x K and K x P interactions were found. Significant positive linear relationships were found between total N and P concentrations in P-YFEL for both the experimental sites (r = 0.46-0.84) and commercial crops (r = 0.43-0.61). Except at site 1 (r = 0.85), total N and nitrate-N concentrations were not highly correlated. For 1 experimental site and for all the growing regions, there were significant negative linear relationships between nitrate-N and chloride concentrations in P-YFEL (r = -0.38 to -0.83). We suggest that the synergism between total N and P and the negative correlation between nitrate N and chloride are important factors to be considered to ensure reliable interpretation of early-season, petiole plant test data for these nutrients in potato crops; that the critical P and total N concentrations are different for Kennebec and Atlantic; and that when K is not yield-limiting, the main effects and interactions between K and total N, P, or nitrate-N do not confound the use of these nutrients in P-YFEL to assess the P, N, or K status of potato crops. |
