Study On The Tuber Quality And Plant Nitrogen Status Diagnosis Of Potato Under Different Nitrogen Levels

The effects of different nitrogen levels on potato nitrogen status, potato tuber yield and quality were studied in the field trial in Hohhot using Kexin-1The main results were as followings:1. The potato tuber yield increased with the increase of nitrogen levels, when nitrogen level was 16kg/667m2, the tuber yield reached the peak.2. The tuber nitrate content, soluble protein, soluble sugar and reduce sugar contents increased, while starch content decreased.with the increase of nitrogen rates.3. The Maximal uptake of nitrogen by potato plant occurred at tuber initiation stage to tuber bulking stage, and plant nitrogen accumulation reached the greatest at starch accumulation stage. Agronomic efficiency (AE) and Physiological efficiency (PE) of nitrogen fertilzer increased with the increase of nitrogen rates when the nitrogen was less than 18kg/667m2, above it,they were decreased with nitrogen rates. Recovery efficiency (RE) and Partial factor productivity of applied N (PFP) decreased with the increase of nitrogen rate.4. Significant correlations between SPAD readings and chlorophyll content, total N of shoot, relative yield existed, and the critical SPAD values for Kexin-1 in Hohhot were established in different growth stages. It was 47.3, 45.1 and 40.2 respectively at stages of tuber initiation, bulkingand starch accumulation. Basing on literatures and present research, mathmatics model about potato yield and N applying rate, indexes of nitrogen diagnosis were established; the models were used to recommend the nitrogen topdressing rates in tuber initiation stage, tuber bulking stage respectively: Tuber initiation stage N(kg/667m2)=(2.4-0.05×x)(0.16×x-1.5)×1.09; Tuber bulking stage N(kg/667m2)=(1.4-0.03×x)(0.16×x-1.5)×1.09; X stands for SPAD reading of forth leaf (form the top of shoot).