Major aggregate breakdown mechanisms

Question 1.
Four plots in a farmer’s field with the same soil type were subjected to different treatments. To determine the influence of the treatments on the stability of the aggregates, soil samples were taken from each plot, air-dried, crushed and sieved through a stack of sieves comprising of a 2 mm sieve on top of a 1 mm sieve. The 1-2 mm air-dried aggregates generated were wetted and subjected to wet sieving using a single sieve apparatus. The water stable aggregates (WSA) values calculated using equation 1 and related soil properties are presented in Table 1.
WSA = MS x 100 —- ————-Equation 1 stst-mu
where Ms is mass of stable aggregates and Mu is mass of unstable aggregates.
a) Analyse the data in Table 1 by calculating useful indices for each plot based on the soil data provided. 5 Marks b) Identify and discuss the major aggregate breakdown mechanisms in each plot. 5 Marks c) Explain the implications of the WSA values and associated breakdown mechanisms on the soil and water management of the different plots. 5 Marks
Table I: Water stable aggregates (WSA), wetting rates and some soil chemical properties of the four plots
Wetting rate pH EC Nat Organic matter CEC WSA (dS/m) (cmol kg-1) (%) (owl kw (%) I)

Sample Solution