The decomposition of plant leafy biomass and their manure derivatives in Kolikoro, Mali

After farmers apply either plant leafy biomass or animal manure in their farms how long does it take for nutrients to be available to crops?

Plant foliage in sealed and unsealed litterbags. (Photo: Siriki Fane)

This graphs shows the weights of the buried bags of foliage and manure decreasing over the weeks.

Plant foliage and manure decomposition patterns in Koulikoro, Mali.

Introduction

Decomposition encompasses all the physical, chemical, and biological processes by which organic matter breaks down in the soil to release CO2, and nutrients for plant growth (Aerts, 1997). The decomposition process is controlled by climate, soil fertility, and organic matter quality (Aerts, 1997). However, under the same climate and soil fertility, organic matter quality is the important factor controlling decomposition. Several research projects conducted in the Sahelian Region of West Africa have shown the improvement of crop yield and soil fertility when either plant leafy biomass or animal manure is used to fertilize crops (e,g. Kaya and Nair, 2001). Considering that the above-mentioned organic amendments are of different quality, our study sought to estimate and compare the rate of decomposition of these organic amendments.

Materials and methods

The decomposition study was undertaken in Koulikoro, Mali by placing 17 g of the foliage of four selected plants (Khaya senegalensis, Pterocarpus lucens, Ficus sycomorus, and Pennisetum pedicellatum) and their manure derivatives into 20 cm × 20 cm litterbag with a mesh size of 2 mm. Filled litterbags were collected at week 0, 4, 8, 16, and 32 after their placement at 1-2 cm depth in the soil. After collection, contents from the litterbags were oven dried and weighed.

Results

After 4 weeks of litterbag placement on the soil surface, manure and plant foliage lost 80% and 50% respectively of their initial dry weight (Fig 2). Consequently, the rate of decomposition in manure was 50% greater than plant foliage.

Conclusion

To synchronize the nutrient requirements of crops with the nutrient release from mulch, farmers can either use manure or plant foliage. For crops whose nutrient requirements are high shortly after planting, manure is recommended whereas those whose nutrient requirement peaks at a later time after planting then plant foliage is recommended.

Works Cited

Aerts R (1997) Climate, leaf litter chemistry and leaf-litter decom- position in terrestrial ecosystems—a triangular relationship. Oikos 79:439–449

Kaya, B., Nair, P.K.R. Soil fertility and crop yields under improved-fallow systems in southern Mali. Agroforestry Systems 52, 1–11 (2001). doi.org/10.1023/A:1010717629129