Response of shallots to different rates of nitrogen grown in the lowland tropics of Cirebon Regency, West Java

Abstract

Abstract Nitrogen (N) is a basic macronutrient required for plant growth and productivity. However, in Indonesian shallot production, there is a tendency to overuse nitrogen, leading to soil degradation and adverse environmental impacts. To address the impact of excessive nitrogen application, an experiment was carried out in a farmer’s field in Ciledug (12 m above sea level), Cirebon, West Java, Indonesia. The aim was to study the response of shallot (Allium cepa var. aggregatum) to different nitrogen rates in the lowland tropics. Seven different levels of nitrogen rates (0, 40, 80, 120, 160, 240 and 320 N kg ha−1) were applied in a random complete block design with four replications, using the shallot variety Bima. As nitrogen application increased, the amount of foliage, bulb, and overall nitrogen uptake increased, reaching the highest level at 320 kg N ha−1, with a total nitrogen uptake of 70 kg N ha−1. Despite the increase in yield with higher nitrogen application rates, the percentage of nitrogen absorbed by the crop decreased significantly. At the highest treatment yield (16.3 t ha−1 at 320 kg N ha−1), the difference between the nitrogen applied and the amount taken up by the crop was approximately 250 kg N ha−1, without considering the uptake of mineralized nitrogen provided by the soil. The fresh yield data was used to fit a quadratic regression model, which resulted in a correlation coefficient (r2) of 0.963. It was found that the most effective maximum yield values occurred at approximately 240 kg N ha−1. There is a need for strategies to enhance nitrogen use efficiency in order to lower fertilizer expenses, enhance crop productivity, and minimize environmental impact.