Root depth and nitrogen uptake from deep soil layers in organic vegetable production -- a preliminary study.

摘要

Deep-rooted crops that uptake nitrate from deep soil layers may be used as a tool to increase nutrient use efficiency in crop rotations. A study on deep root growth and N uptake by catch crops (winter rye, winter rape) and vegetables (maize, carrots, white cabbage) on a sandy loam soil under organic farming practice in Denmark was established in 1999 and 2000. Root depth was registered regularly over the season by the use of minirhizotron method, and uptake of nitrate from deep soil layers was studied by deep point injection of Na15NO3 followed by harvest of aboveground biomass after 5 days. The ability for deep root growth ( > 100 cm) was found to be common among catch crops and vegetables. White cabbage had deep root growth with an average deptharound 220 cm at the beginning of September. Both catch crops had significant 15N uptake from deep soil layers (130 cm depth). The 15N results from the vegetable experiment are not yet available. Overall deep soil N was indicated to be a potentially important source of N for catch crops and vegetables that have the ability to extend root growth to deep soil layers. The results further show that restriction of root measurements to upper soil layers ( < 100 cm) may give erroneous conclusions on root depth and N dynamics.