Placement methods for liquid nitrogen fertilizer applicationin ratoon cane

摘要

Nitrogen is essential to the nutritional balance for ratoon cane, mainly, during sprouting and vegetative growth. In Brazil, the nitrogen fertilizer in ratoon cane is commonly supplied by granular fertilizer application, using soil surface or incorporated into the soil through furrows. In application by furrows, the mechanical operation is hampered by mulching layer from harvest (10 up to 20 Mg ha-1), beyond partial damages in root system of plants. Already to the soil surface application, N-fertilizer uptake efficiency can be decreased due to losses, such as, ammonia volatilization and microbial immobilization. To fill the gap, an alternative method by liquid fertilizer injection through soil drilling has been proposed to improve the efficiency ofN-feiiilizer in ratoon cane. The strategy can supply liquid N-fertilizer near to the root system, with minimum mobilization of soil, roots and straw. Taking into account the proposed method, the objective was perform evaluation considering different placement methods for liquid N-fertilizer applied in ratoon cane area, such as: surface application and N-fertilizer incorporation into the soil using furrows or soil drilling process. The experiment was installed on ratoon cane area (1st cycle), in period of May of 2014. To provide the recommendation rate of 100 kg ha-1 of N, it was used a compound of ammonium nitrate (32% of N) dissolved with water, creating a mixture of 18% of N. The evaluation was performed by monitoring of chlorophyll index (measured by SPAD-502) and number of shoots. From evaluation, it was observed the highest level for chlorophyll index and number of shoots along the intermediate phase, during the vegetative growth, when, ratoon cane needs the higher amount of N-nutrient. But, no significant differences were found to placement methods. However, the proposed method can help to preserve the soil, mulch and roots; furthermore, it can be used as an alternative technique to N-fertilizers sources with high ammonia volatilization.