Supplementary file 1_Soil and crop productivity under on-farm vermiculture-based farming system at smallholder rates in the sub-humid tropics.docx

Introduction

Vermiculture-based manures such as vermicompost and its byproducts like vermiculture are gaining importance as viable alternative soil amendments. This is practically feasible, especially in subsistence farming, by replacing common organic and synthetic inputs that are often costly and inaccessible to farmers. However, the effectiveness of vermiculture tea as a sole amendment or in combination with other inputs has not been tested under field conditions. Moreover, its longterm impact on soil and crop productivity has not been established.

Methods

We conducted an on-farm field study in farmers' fields to evaluate the effects of sole vermiculture tea (Vermi), in combination with other organic amendments (VermOrg), and with synthetic fertilizers (VermInt) applied at subsistence rates on soil properties and crop productivity. We conducted the field experiment for 8 years in a 3-year maize-legume-potato-based crop rotation.

Results and discussion

The subsistence (low) input rates applied led to mining or maintained soil nutrient levels. Sole vermiculture tea yielded significantly (p < 0.01) higher maize grain in most of the experimental seasons, while VermInt recorded significantly (p < 0.01) higher potato tuber yield in all the cultivation seasons. The overall yields of all the rotation crops were low due to the application of suboptimal input levels and insufficient precipitation, especially during vegetative stages.

Conclusion and recommendations

Vermiculture tea could be a viable fertilization alternative, but it does not attain the productivity potential of soil and crops at low-input levels. We recommend optimal application rates of vermiculture tea, as its production is rapid and flexible for scaling for the improvement of crop productivity.