LOW-N TOLERANCE, N-USE EFFICIENCY AND RESPONSIVENESS OF 37 Chenopodium quinoa GENOTYPES UNDER ORGANIC AND MINERAL FERTILIZER CONDITIONS

Low nitrogen (N) fertilizer rate causes negative effects on quinoa productivity; such effects differ from genotype to genotype and from fertilizer type to another. The objectives of the present investigation were: (i) to assess the low-N stress tolerance index (STI) of 37 quinoa genotypes under organic and inorganic fertilizers, (ii) to estimate the superiority of tolerant (T) to sensitive (S) genotypes for studied traits and (iii) to identify high yielding, low-N tolerant, N-efficient and N-responsive genotypes under each fertilizer type. A two-year field experiment was conducted, using a split split-plot design with three replications. Main plots were devoted to two fertilizer types, namely organic (compost) and inorganic (ammonium nitrate), sub-plots to three N rates, namely LN (71.4), MN (142.8) and HN (214.2 kg N/ha), and sub sub-plots to 37 quinoa genotypes. Seed yield/ha (SYPH) of T genotypes was significantly (P≤0.01) superior to S genotypes by 308.8, 123.8, and 152.6 % under organic fertilizer and 100.6, 123.6, and 212.6 % under mineral fertilizer, for LN, MN, and LN, respectively. Superiority in SYPH was associated with significant (P≤0.01) superiority in seed yield/plant (SYPP) and its components, economic (NUEe) and biological (NUEb) N-use efficiency traits under both fertilizer types. Based on STI and seed yield under HN and LN, the genotypes Nat-1, R-103 and Sekam-Bitter, under LN and HN organic fertilizer, Misr1 Improved, R-103 and Giza-1 under LN mineral fertilizer and Agritec-Beige, Egyptian White and, CICA-17, under HN mineral fertilizer conditions, were the most N efficient, most low-N tolerant and the highest seed yielders under respective environments. These genotypes should be recommended to quinoa breeding programs to develop high-yielding varieties for growing under respective low-N as well as high-N organic and inorganic fertilizer conditions.