Impacts of farming systems on soil mineral nitrogen levels in irrigated processing tomatoes

Precise management of soil mineral nitrogen (N) is necessary to optimize the profitability of a farming system and to minimize groundwater pollution by reducing N leaching. Organic and low-input farming systems are alternatives to conventional systems for sustainable soil fertility. Little information is available, however, on the effects of these farming systems on soil mineral N availability. Evaluation of a 4-year rotation of organic (no synthetic fertilizer or pesticide use), low-input (reduced amount of synthetic fertilizer and pesticide use), and conventional (synthetic fertilizer and pesticides applied at conventionally recommended rates) (conv-4) fanning systems, and a conventional 2-year rotation (conv-2) on potentially mineralizable nitrogen (PMN) and soil mineral N levels in irrigated processing tomatoes (Lycopersicon esculentum L.) was conducted after 10 years of management. The organic and low-input systems showed 112% and 36% greater PMN pools than the conventional system, respectively. However, nitrogen mineralization rate in the conventional system was 100% greater than in the organic and 28,70 greater than in the low-input system. Organic and low-input systems showed a small but continuous supply of mineral N during the cropping season, while the conventional systems supplied mineral N as fertilizer pulses.