A technique for selecting potato (Solanum tuberosum) genotypes with low nitrogen requirement

The technique consists of fitting the quadratic model to find relationship between yield of a genotype and N rates, followed by determination of N dos e tiw getting maximum yields of each genotype including the standard cultiv ar. The maximum yield of standard cultivar is termed as fixed yield target. The dose of N far achieving the fixed yield target by a genotype is determ ined and genotypes requiring less N than standard cultivar are designated a s low-nitrogen requiring genotypes. Methods were also developed to determin e the relative and absolute ecofriendly indices of N of the genotypes compa red to standard cultivars. Based on the technique, 'PJ 376' ('Kufri Ashoka' ) was identified as low-N requiring' early duration potato (Solanum tuberos um L.) genotype from the tuber yield data of the field experiments conducte d at Modipuram from 1991-92 to 1993-94. It required 65 kg N/ha compared to 194 kg Na/ha for 'Kufri Chandramukhi' (standard cultivar) for attaining a f ixed tuber yield target of 33.4 tonnes/ha. In the medium duration 'MS 78-46 ' required 133 kg N/ha compared to 211 kg N/ha by 'Kufri Bahar' (standard c ultivar) far attaining yield target of 41.7 tonnes/ha. The 'MS 78-46' and " Kufri Ashoka' were more ecofriendly as their relative and absolute ecofrien dly indices were higher than the standard cultivars. 'Kufri Ashoka' was mor e efficient in utillizing N from soil,while 'MS 78-46' was more efficient i n utillizing N from soil as well as fertilizer source than the standard cul tivars.