Decision-making on the optimum timing for nitrogen fertilization on sugarcane ratoon

Castro, Sérgio Gustavo Quassi deRossi Neto, JoãoKõlln, Oriel TiagoBorges, Bernardo Melo Montes NogueiraFranco, Henrique Coutinho Junqueira

Low efficiency of nitrogen from fertilizers is a major concern worldwide, threatening the sustainability of sugarcane production. The N use efficiency (NUE) by sugarcane can be improved by adopting better fertilizing management practices, reducing environmental impacts. This work evaluated the effects of varying N rates and time of application on stalks and sugar yield in ratoon harvested early in the crop season. The experimental design was a randomized block in a 2 × 4 factorial design and a control (no N) with five replications, including two application times (45 or 90 DAH – days after harvest) and four N rates (50, 100, 150, or 200 kg N ha−1). The time of N fertilizer application promoted differences in stalk yield, as the cumulative yield of two harvests was increased by 8 % (15 Mg ha−1) at 45 DAH when compared to the application at 90 DAH. The application performed at 45 DAH augmented sugar yield by 10 % (2.8 Mg ha−1 of sugar) in relation to 90 DAH. The N rates that promoted the highest sugarcane yield were, respectively, 122 and 144 kg N ha−1 in the first and second crop cycles. The average economical rates obtained for the first and second agricultural cycles were, respectively, 104 and 127 kg N ha−1, demonstrating that the gains by applying high amounts of fertilizers (rates above 150 kg N ha−1) may not cover the investment.(AU)

1. green cane
2. N fertilization
3. sugarcane yield
4. economical rate