Nitrogen contributions of legume roots to cabbage nutrition

Thiago de Oliveira Vargas, Ellen Rúbia Diniz, Ricardo Henrique Silva Santos, Segundo Urquiaga, Paulo Roberto Cecon
2013 Scientia Agricola  
The effects of roots are generally not considered in studies assessing crop responses to green manure. However, measuring such effects can contribute to a better understanding of crop rotation. In two experiments, we evaluated the content of legume-N in crop tissue and the fertilizer value of the roots and shoots of two legume species. Roots, shoots, or whole plants of the legumes sunhemp (Crotalaria juncea) and jack beans (Canavalia ensiformis) were cropped as green manure to supply nitrogen
more » ... cabbage crops (Brassica oleracea var. capitata). The principle of the A-value technique was applied to estimate the fertilizer value of each plant part. In a pot experiment, both the content of legume-N in cabbage and the fertilizer value of the whole plant was higher than the shoots, which was in turn higher than that of the roots. In fi eld condition, roots had a decreasing effect on the N content of cabbage plants. Growing cabbage on legume root residue resulted in an increased absorption of 15 N-urea, resulting in negative values for legume-N content: -13.59 g kg -1 and -3.51 g kg -1 for sunhemp and jack beans, respectively. Suggesting both low N supply by roots and N immobilization in soil organic matter or microbial biomass. Future research should focus on estimating the net N acquisition by plants from root residues under fi eld conditions, where rooting patterns and biomass distribution differ from those in pot experiments, therefore giving a more realistic quantitative estimate.
doi:10.1590/s0103-90162013000600006 fatcat:ndnwbpuzpnbuvfgxpdbyyfonru