Cowpea N rhizodeposition and its below-ground transfer to a co-existing and to a subsequent millet crop on a sandy soil of the Sudano-Sahelian eco-zone

Abstract

Nitrogen (N) rhizodeposition by cowpea (Vigna unguiculata (L.) Walp) is potentially a large N source in cropping systems of Sub-Saharan Africa. A field experiment was conducted to measure cowpea N rhizodeposition under the conditions of the SudanoSahelian zone using direct 15 N labelling techniques to trace the amount of deposition and its transfer to associated and subsequent crops. Half of the total cowpea crop N was located below-ground at plant maturity, which exceeded 20 kgN ha −1 when intercropped with millet. Only 15% of the below-ground cowpea N was recovered in roots, while 85% was found in the rhizodeposited pools. The experiment demonstrated that direct below-ground N transfer occurred from cowpea to millet in intercrop at a rate of 2 kgN ha −1 over the growing season. Forty percent of the 25 kg below-ground N that the cowpea crop left at harvest were identifiable in the top 0.30 m soil in the beginning of the next planting season 7 months later; a pool still present at the end of that second season. Thus, the subsequent crop of millet (Pennisetum glaucum (L.) R. Br.) only recovered 2.5 kgN ha −1 from the below-ground cowpea pre-crop N during this growth season. The role and potential of cowpea as N provider has been underestimated in the past by ignoring the large proportion of N contained in its Plant Soil (2011) 340:369-382

To Meet Future Food Demands We Need to Change from Annual Grain Legumes to Multipurpose Semi-Perennial Legumes

“…That makes the use of annual leguminous crops a sustainable approach. Under tropical conditions, however, leguminous nitrogen cannot be conserved and controlled in the same manner and thus transfer to subsequent crops when using annual crops are small (Laberge et al, 2011). That may not make the use of annual leguminous crops an unsustainable approach but clearly the nitrogen pools left by the crops are lost and not available to the subsequent crop.…”

“…This approach ignores the depositions belowground associated with crop roots (Gregory, 2006); deposits can benefit subsequent crops (Laberge et al, 2011).…”

“…The initial transfers of nitrogen from annual grain legumes to subsequent crops are relatively small (Høgh-Jensen et al, 2005;Laberge et al, 2011). However, Høgh-Jensen et al (2006) concluded that N-rich leaf litter together with root residues from pigeonpea grown as annual crops well into the dry season is able to enhance a sustainable maize yield that is approximately twice the yield of maize grown in sole stand.…”

Agronomic Management of Cowpea for High Grain Yield and Sustainable Agriculture in Western Indo-Gangetic Plain of India

“…Furthermore, cowpea can be grown as a sole crop as well as an inter crop (Bhilare et al, 2001;Singh et al, 2005) and can contribute nitrogen in the form of biological nitrogen fixation (Rusinamhodzi et al, 2006;Nyemba and Dakora 2010;. Cowpea can play an important role in cropping systems not only due to nitrogen fixation or nitrogen contributed through crop residues after harvest but also due to nitrogen in rhizodeposits (which include root exudates, fine roots and root necrosis products accrued in the soil during plant growth) (Laberge et al, 2011). There is, therefore, a need to include cowpea in different cropping systems.…”

Variability of cowpea (vigna unguiculata l.) nodulation: what efficiency in use of the rhizobial symbiosis for plant growth under zaï cultivation in sub-saharan agro-ecosystem of burkina faso?

“…It is concluded that the measurements of nodulation and growth of cowpea at flowering stage may contribute to optimize the organic fertilization of cowpea in zaï intercropping with sorghum and the subsequent improvement In view of the high proximity of the seedlings of both species vantage of the zaï sowing could be the increase in positive interactions between the cereal and the legume, in particular for the processes of N 2 fixation by the legume and N transfer to the cereal by either rhizo-deposition decomposition (Fustec et al 2011;Laberge et al 2011). However, few information exist on the nodulation of cowpea and its efficiency for the crop growth in the farmers' fields under zaï sowing in Sub-Saharan Africa.…”