Conservation Agriculture in Zambia: Effects on Selected Soil Properties and Biological Nitrogen Fixation in Soya Beans (Glycine max (L.) Merr)

Abstract

<p>Conservation agriculture has been promoted in Zambia as a strategy to mitigate some of the negative effects arising from conventional tillage practices. Conservation agriculture offers several potential benefits on soil properties. However, these benefits and impacts vary across agro ecological regions and management practices. This study investigated changes, over time, associated with the practice of conservation agriculture in selected soil chemical, physical and biological properties, including an assessment of the effects on soil respiration, nodulation and biological nitrogen fixation in soya beans (<em>Glycine max </em>(L.) Merr). Six paired soil samples were collected from conservation agriculture and conventional tillage fields. Fields under conservation agriculture were 4, 7 and 16 years old while those under conventional tillage had been cultivated for over 18 years. Changes in soil properties due to conservation agriculture practice were determined using published laboratory procedures and compared using the paired t-test at 95% confidence level. The results indicated significantly higher soil pH, soil organic carbon, nodulation and biological nitrogen fixation under conservation agriculture than conventional tillage after seven years of practice. The study also showed significantly higher total porosity, soil microbial biomass, soil respiration and lower soil bulk density after sixteen years of practice. Based on these results, the practice of conservation agriculture has potential to improve crop productivity by improving the different aspects of soil fertility, the length of time before this is realized notwithstanding. Further studies that compare several conservation agriculture systems are recommended in other agro-ecological zones of the country to validate these findings.</p>

Influence of Various Tillage Practices on Soil Physical Properties and Wheat Performance in Different Wheat-based Cropping Systems

“…The CA benefits include less fuel consumption (Baker et al, 2007;Tahir et al, 2008;Lithourgidis et al, 2009;Akbarnia and Farhani, 2014), reduced soil loss due to enhanced aggregate stability and the protective effect of crop residues left over the soil (Friedrich et al, 2011;Sanderson et al, 2013;Vanlauwe et al, 2014). It is more productive as compared to conventional tillage because it improves soil quality and water use efficiency of plants (Samarajeewa et al, 2006;Brunel et al, 2013;Muchabi et al, 2014). Conservation tillage creates more continuous pore systems and reduces the soil porosity for aeration but increase the capillary porosity, helps improving soil water holding capacity (Bhattachariya et al, 2008;Kishor et al, 2013).…”

Chemical and Biological Properties of Soils Under Maize-Cowpea Cropping Systems in Conservation Agriculture

“…Cropping sequence did not influence soil microbial biomass or activity. Earlier findings have shown that significant changes in soil microbial biomass in soils under CA are apparent only after 16 years of practice (Muchabi et al, 2014); this suggests that the length of time of practice in this case being only six years might have been too short to elicit observable changes.…”

“…Length of time under CA practice is also an essential factor determining SOC accumulation over time (Blanco-Canqui & Lal, 2007). Studies by Umar et al (2011) and Muchabi et al (2014) in Lusaka, Eastern, Southern and Central provinces of Zambia suggested that five years of CA practice would not be long enough for the effects to be significant but waiting for seven years would result in sufficient SOC accumulation. That this soil had been under CA practice for only six years could explain why SOC levels were still low and, in some cases, not significantly higher than under conventional farming.…”

“…Further, while many on-station and on-farm trials have been conducted to evaluate changes in soil properties and crop yield, there is still only partial understanding of the interactions of different tillage practices, cropping sequences, soil cover types and properties, crop residue properties, soil macro-and micro fauna, and underlying mechanisms of nutrient cycling (Whitfield et al, 2015). Previous research on the effects of CA on soil properties in Zambia have suggested that changes in soil chemical and biological properties may take many years before they are evident (Muchabi, Lungu, & Mweetwa, 2014); these changes must go through particular phases which also are strongly influenced by farmer practice. The lack of quick results could be a discouraging factor leading to disadoptions and therefore, presenting a need for farmer sensitization of this aspect of CA adoption.…”

“…The paper focuses specifically on maize-cowpea cropping sequences and their effects on soil properties and biological nitrogen fixation capabilities of cowpea. The paper builds on earlier work in Zambia that show the influence of length of time of practice (Muchabi et al, 2014) and cropping sequences (Thierfelder, Cheesman, & Rusinamhodzi, 2012) on soil chemical, physical and biological properties under CA.…”