Effect of organic amendments on soil aggregate stability in Chipata and Kasama, Zambia

Organic amendments have been known to improve soil physical and chemical properties in sub-Saharan Africa. However, research information on how organic amendments affect aggregate stability and the degree of their effects in comparison to others is indaquate in Zambia. The study was therefore carried out to assess the effect of organic amendments on soil aggregate stability and organic matter content on soils from Chipata and Kasama, Zambia. The specific objectives were (i) To assess the effect of organic amendments on soil aggregate stability on two Zambian soils. (ii) To assess the effect of organic amendments on soil organic matter and soil aggregate stability of two Zambian soils.(iii) To assess if there is a relationship between soil organic matter and soil aggregate stability. Soil aggregates were collected from the top 10 cm of 10 m x10 m plots in each treatment replicated five times. These aggregates were sieved through a 9.5 mm, and the retained aggregates on an 8 mm sieve were collected and used for aggregate stability analysis. Analysis of variance (ANOVA) of results showed significant differences among the means of four treatments; Sun hemp, tephrosia vogelii alley cropping, pigeon pea alley cropping, Animal manure, and conventional treatments on a loamy ferric luvisol. Amending soils with Sunhemp showed a significantly higher mean weight diameter (MWDd) of 2.393 compared to amending soils with tephrosia vogelii alley cropping MWDd 1.767 (P value <0.001***). There was a highly significant difference in the organic matter content for the Ferasols at Misamfu (P value 0.002**). The difference was significant in larger aggregates than smaller aggregates. There was a significant correlation in the 7.18 mm and 1.9 mm aggregate size distribution for Ferasols at Misamfu with Pearsons correlation of 0.292* and -0.334** respectively. Hence for a loamy ferric luvisol soil, Sunhemp and animal manure may be used to improve the condition especially for aeration and aggregate stability. Aggregate stability information is an important physical parameter that has several effects on several soil properties that can be used to improve soil productivity in Agricultural production.
Key words: Aggregate stability, Organic amendments, Organic matter, Soil aggregates.