Effect of Irrigation Type on Soil Functions, Root Systems and Crop Nutrition in Organic Tomato and Corn.

Attempts to improve agronomic water use efficiency by introducing subsurface drip irrigation have met with mixed results in organic systems. Growers point to unavailability of nitrogen from organic inputs as a potential cause of poor performance when crops are grown under drip irrigation, but little information exists on organic nutrient cycling under different irrigation schemes. The objective of this study was to examine the effects of irrigation scheme on soil and plant characteristics of an organic production system. We examined the following aspects of carbon and nitrogen cycling as they relate to soil water movement under two different drip irrigation arrangements and compared them to furrow irrigated plots in organic tomato and corn rotations: 1) crop root system, 2) microbial activity, 3) cover crop decomposition and nitrogen mineralization, and 4) total plant nitrogen uptake. Our results have implications for the feasibility of implementing drip irrigation systems in organic agriculture with regard to crop production and water and nitrogen use efficiency.