Calcium cyanamide effects on nitrogen use efficiency, yield, nitrates, and dry matter content of lettuce

A 2-yr field study was conducted to evaluate the effects of calcium cyanamide as an alternative nitrogen (N) fertilizer source on N use efficiency (NUE), yield, and quality of two types of lettuce (Lactuca sativa L.), romaine (var. longifolia, cv. Manavert) and red oak-leaf (var. crispa, cv. Aruba), grown on clay soil under a Mediterranean environment. Pretransplanting application of 120 kg ha−1 of N as calcium cyanamide (120CC) was compared with a traditional split application of 120 kg ha−1 of soluble N (120SN) consisting of 50% ammonium sulfate applied before transplanting and 50% as ammonium nitrate applied after transplanting. An unfertilized control (0-N) was included to calculate NUE indices. At harvest leaf area index, dry weight, fresh yield, dry matter concentration, and NUE indices were not affected by the N source. Leaf nitrate (NO3–) content was on average 55 and 41% higher in Aruba than in Manavert in the first (Exp-1) and second (Exp-2) season, respectively. Plants fertilized with 120CC had lower leaf NO3– content (41 and 18% in Aruba and 70 and 21% in Manavert in Exp-1 and Exp-2, respectively) compared with those fertilized with 120SN. These results suggest calcium cyanamide may be used as an effective tool to reduce leaf NO3– accumulation and to produce high quality lettuce in compliance with European Regulation No. 1258/2011 while assuring competitive yields.