Impact of Direct Seeding Mulch-Based Cropping Systems on Soil Health in the Guinea Savanna Zone of Ghana.

Declining soil fertility is a major constraint to agriculture productivity in Northern Ghana. Adoption of sustainable soil intensification practices such as direct seeding mulch–based cropping systems (DMC) can potentially reverse the trend and provide food for the growing population.  The objective of this study was to assess the effect of DMC on soil health. The experiment was conducted at the Savannah Agriculture Research Institute (SARI) located in Nyankpala, Ghana. The experimental design was a split plot arranged in randomized complete block design.  The main treatments consisted of five different cropping systems: DMC1 (maize and Stylosanthes guianensis), DMC2 (maize and Black Dolichos lab lab), DMC3 (maize and cowpea), CC1 (mixed strand of Braccharia ruziziensis, Stylosanthes guianensis, Crotalaria juncea, Crotalaria retusa) and CK (maize as check). The sub-plot factor was fertilizer using NPK fertilizer at the following rates: 0-0-0 (control), 30-30-15 (half recommended rated) and 60-60-30 (full recommended rate) kg ha^–1.  Soil samples were taken from 0-5 and 5-15 cm depth in June 2014. Analyses included potentially mineralizable N (PMN), soil organic carbon (SOC), Total N (TN), microbial respiration, microbial biomass, and soil pH.  Biomass yield (kg ha^-1) was recorded at harvest. DMC cropping systems yielded significantly higher biomass compared to CK in 2012 and 2013.  Soil microbial biomass and activity was not affected by the treatments. High plant biomass produced by DMC1 and DMC3 did not increase SOC and PMN relative to CK. Fertilizer application significant increased plant biomass production resulting in a significant increase in SOC and PMN in the 0-5cm depth. DMC cropping systems and fertilizer decreased soil pH in 0-5cm depth. In conclusion, both organic and inorganic soil amendments may be utilized to improve soil chemical and biological properties in the Guinea Savanna zone of Ghana however low soil pH could hinder improvement in soil health.