Effects of Nitrogen on Yield and Chlorophyll of Potato (solanum Tuberosum L.) Cultivars

Effects of nitrogen on the leaf chlorophyll (chl), yield and yield attributing characters of potato as tuber number and mean tuber weight were studied. Correlation coefficients between the investigated characters were determined. Five nitrogen rates (0, 150, 200, 250 and 300 kg/ha) and four potato cultivars (Burren, Slaney, Anna and Emma) were used in the study. First, second, third class tuber yields and total tuber yield, tuber number per plant, and leaf chl were significantly influenced by both nitrogen rate and cultivar, whereas mean tuber weight was affected only by cultivar. Maximum total yield was obtained at 200 kg N/ha. There was significant linear relationship between leaf chl and N applied (R=0.91). There were significant correlations between chl and yield and yield related characters. Total yield significantly correlated with leaf chl. Correlations between first class yield and total yield as well as total yield and tuber number per plant were highly significant. Introduction Nitrogen is of vital importance for plant growth due to being a part of amino acid, protein and chlorophyll molecule (Gilbert 1949, Tisdale and Nelson 1956). Potato needs large amount of nitrogen. Therefore, adequate N fertilization is critical for optimizing potato yield and quality (Westermann and Kleinkopf 1985, Westermann et al. 1988). Insufficient available N leads to reduced growth, reduced light interception, limited yield and early crop senescence. On the otherhand, excessive available N can result in reduced yield, delayed tuber set and reduced tuber dry matter content (Kleinkopf et al. 1981). Chlorophyll meter (Minolta) uses light sources and detects the light transmitted by a plant leaf at two wavelengths (at red and infrared region of the spectrum). This has been used for determination of N requirements of many crops including corn (Piekielek et al. 1995, Blackmer and Schepers 1995, Varvel et al. 1997), wheat (Singh et al. 2002), rice (Turner and Jund 1991, Singh et al. 2002) and potato (Shaaban and El-Bendary 1999, Denuit et al. 2002). Yadava (1986) working with 22 species representing 14 plant families found significant correlations between chl meter reading and chl concentration determined by a conventional technique. Vos and Bom (1993) reported that chl meter reading was well correlated with laboratory measurements of chl content and with the nitrogen concentration in leaves of potato (r>0.95). Wu et al. (2007) compared petiole nitrate concentrations, chl meter readings and satellite imagery to detect nitrogen status of potato canopies by applying six N rates from 34 to 270 kg/ha. They found that overall treatment variations in chl meter readings were consistent with those in petiole nitrate nitrogen (NO3-N) concentrations. Madeira et al. (2003) reported that in situ chl meter readings and extractable chl content were highly correlated with, both for chl a (r=0.93) and total chl (r=0.89). The aims of the present study were to determine yield, yield attributes and leaf chl content of potato as influenced by nitrogen application on crop cultivars and to find out the relationships among these characters. *E-mail: [email protected]