Root growth and nitrogen uptake of carrot, early cabbage, onion and lettuce following a range of green manures

Abstract

An experiment was performed to study the significance of rooting depth of four vegetable crops on their utilization of green manure nitrogen (N). Rates of rooting depth development were estimated as approximately 0.2, 0.7, 1.2 and 1.2 mm day °C−1 for onion, carrot, lettuce and cabbage, respectively. At harvest, onion and lettuce were found to be shallow‐rooted with final rooting depths of only 0.3 and 0.6 m, respectively, whereas carrot and cabbage reached rooting depths of at least 1.1 m. The two deep‐rooted vegetables increased their N uptake by 46, 24 and 7 kg N ha−1 when following winter‐hardy legumes, non‐hardy legumes and rye, respectively; the equivalent responses by the two shallow‐rooted crops were 23, 9 and 15 kg N ha−1, respectively. Thus the deep‐rooted crops used the legume N more efficiently but the shallow‐rooted crops made better use of N left by the non‐legume rye crop. These interactions between green manure type and vegetable crop N response are the result of the dual effects of the green manures: biological N fixation by the legumes, and the variable ability of the green manure crops to concentrate available N in the topsoil. Before shallow‐rooted crops, the ability of rye to concentrate N in the topsoil may be as important as the N fixing ability of legumes.

The effect of catch crop species on selenium availability for succeeding crops

“…The higher Se concentrations in cabbages compared to onions may be caused by the deeper root growth of cabbages which increases their access to more soil Se in deeper soil layers. Early harvested cabbage types were found to have root depths of at least 1.1 m compared to the more shallow-rooted onions which reached only 0.3 m ( Thorup-Kristensen 2006).…”

Influence of root zone nitrogen management and a summer catch crop on cucumber yield and soil mineral nitrogen dynamics in intensive production systems

“…Frequent and excessive N side-dressing and irrigation are major features of conventional management systems, and are employed to maintain adequate N concentrations in the root zone. The result is poor control of root zone N supply and ready leaching of nitrate out of the root zone because of the shallow rooting systems of some vegetable species (Thorup-Kristensen 2006;Verma et al 2007).…”

Crop yield, root growth, and nutrient dynamics in a conventional and three organic cropping systems with different levels of external inputs and N re-cycling through fertility building crops

“…A major problem is that green manure crops often are grown the whole growing season and thereby reduce the possibility to grow main crops. Short term green manure strategies using only the autumn after main crop harvest may be quite effective (Thorup-Kristensen, 2006b;Sørensen and Thorup-Kristensen, 2003), and they allow green manures to be grown much more frequently in the rotation and at lower cost. Intercrops are living mulches that are grown together with the main crops.…”

“…Fertility building crops are management tools to reduce the need for external N inputs and losses to the environment, like legume green manures that increase N input through atmospheric N fixation (Thorup- , and autumn N catch crops that increase N re-cycling by uptake and mineralization at optimized management strategies (Thorup-Kristensen, 2006b;Tonitto et al, 2006;Thorup-Kristensen and Dresbøll, 2010). A major problem is that green manure crops often are grown the whole growing season and thereby reduce the possibility to grow main crops.…”