Partial macronutrient balances of mucuna/maize rotations in the forest savannah transitional zone of Ghana.

Abstract

A study was conducted in 1999 to analyse nutrient balances to assess the potential sustainability of mucuna (Mucuna pruriens var. utilis)/maize rotations in Sunyani, Ghana. Mucuna fixed 105.7 (±11.8) kg/ha in the aboveground biomass representing 57% of the total nitrogen uptake. Due to higher yields, nutrients removed by seeds of maize grown after a mucuna fallow were higher compared to nutrients in seeds of maize grown after a short-season natural fallow. Similar differences existed for the crop residues but losses were low due to cob straw removal while the stalks were left in the field. Farmers harvested 808±88 kg/ha mucuna seeds. The nutrient concentrations of the four samples were 3.76±0.16% N, 0.04±0.01% P, 0.94±0.27% K, 0.59±0.11% Ca and 0.49±0.13% Mg, indicating that 30.4 kg N/ha or 27.3% of the biologically fixed N by mucuna fallowing was lost through seed harvesting, while losses of other elements were rather low. Nutrient losses caused by burning were the major negative nutrient flow in the natural fallow system. Tabulated data are presented on the partial nutrient balance in kg ha-1 year-1 of mucuna/maize rotation and a short-season natural fallow/maize system when the fallow vegetation is burnt. Without burning, the natural fallow system was advantageous over mucuna for all elements except for N. When N was added to the system, other nutrients became more depleted because of increased maize yield levels after a mucuna fallow compared with a natural fallow.

Effect ofMucunaFallow on Weed Dry Matter and Composition in Succeeding Maize

“…Although the difference in weed density in maize after the early maturing Mucuna variety Downloaded by [Eastern Michigan University] at 10:19 11 October 2014 (77 seedlings m· 2 ) was not significantly different from the natural fallow treatment (113 seedlings m· 2 ), the suppressing effect of Mucuna fallow on weeds was still visible. The Mucuna technology reduces the labour demand for land preparation at a time when labour is scarce and plant nutrients are not lost through volatilization due to burning (Anthofer & Kroschel, 2002).…”

“…Similar to experiences in the Derived Savannah of Benin (Honlonkou et al, 1999), one of the main reasons for farmers to adopt Mucuna was its effect on weeds (Anthofer, 2000). Moreover, Mucuna fallow systems imply also a shift from slash-and-bum to slash-and-mulch (Anthofer & Kroschel, 2002) with additional effects on the weed biomass. Therefore, it is important to know by how much Mucuna fallow systems are able to reduce the weed pressure in subsequent maize under on-farm conditions.…”