Nitrogen Use Efficiency Of Potato Cultivated In Sandy Soil.

Correct nitrogen fertilization is essential for potato (Solanum tuberosum L.) cultivation because its undeveloped root system are not able to uptake excessive nitrogen rate applications. This surplus of nitrogen applied in the soil will be lost by leaching and volatilization resulting not only in environmental pollution but also in economic losses, mostly in when the potato is cultivated in sandy soil.  The use of nitrification inhibitors would decrease soil nitrogen losses by decreasing both leaching and volatilization. The objective of this study was to evaluate the effect of different types of nitrogen fertilizers and different rates on potato nitrogen use efficiency and yield in a sandy soil. In 2012, an experimental field, with four blocks in a randomized block design, was cultivated with potato var. Ágata in Avaré, São Paulo State, Brazil. It was compared plant dry matter production, N accumulation, potato yield, and N use efficiency for dry matter and fresh tuber production among three types of nitrogen fertilizers: (i) Entec 26 (Ammonium Sulfonitrate with nitrification inhibitor DMPP (3.4-dimethylpyrazole phosphate), (ii) ammonium sulfate, and (iii) urea which were applied at three different rates such as 80, 120 and 160 kg ha^-1. In addition, replications with no N application were used as control treatment. For plots treated with N rate of 80 kg ha^-1, all N fertilizer was applied at planting; however, N application was divided in 40 kg N ha^-1 at planting and the remainder N was sidedressed at the hilling time for N rates of 120 and 160 kg ha^-1. According to the results, the N rates increased plant dry matter, the nitrogen accumulation and tuber yield regardless to N fertilizer type. Conversely, the N rates decreased N use efficiency for dry matter and fresh tuber production. The N higher rates applied at planting and sidedress promoted higher yield and better N use efficiency than the lowest N rate applied totally at planting. Additionally, Entec 26 promoted higher potato yield than the other evaluated N fertilizer types.

Keywords: Solanum tuberosum, uptake, nitrogen nutrition.