Diagnosing Soil Health Constraints

by | March 30, 2012
Category: News

Field trials across Africa are identifying non-responsive soils

Diagnostic field trials in Nkhata Bay, Malawi, February 2012

Diagnostic field trials in Nkhata Bay, Malawi, February 2012

A key part of the AfSIS project are diagnostic trials, which will contribute to the spatially explicit, evidence-based soil management recommendations to help extension workers, governments, agricultural institutes, farmers, and others tailor agricultural practices to specific soil types. Trials are examining the factors in soil that may limit crop production as well as agricultural practices such as integrated soil fertility management (ISFM).

Trials have been set up in several AfSIS sites in five countries to identify limitations in soils for crop production. Such limitations may relate to macronutrients (such as Nitrogen [N], Phosphorous [P], and Potassium [K]), micronutrients, or other structural limitations such as pH and carbon deficiency.

The analysis examines whether there are common patterns in crop response to fertilizer application and to degradation processes. A key intent is to classify so-called responsive soils — those showing a significant response to fertilizer (NPK) applications — and those that only show a marginal response to fertilizer application. These trials will attempt to understand the factors that make some soils more responsive to fertilizer than others, including whether limitations are due to secondary or micro-nutrient concentrations, low pH values, or deficient soil carbon levels. Dr Jeroen Huising, a senior scientist at CIAT who is leading this effort with other national research organizations, explains that “this information will allow farmers to set realistic yield targets and inform them of the inputs required to achieve these.”

Preliminary results, based on data from 200+ individual experimental fields from sentinel sites in Malawi, Mali, and Tanzania, show three types of response patterns (Figure 1):

Figure 1. Three characteristics crop response patterns derived from 200+ observations (AfSIS diagnostic field trials) using clustering algorithm with expectation-maximization.

Figure 1. Three characteristics crop response patterns derived from 200+ observations (AfSIS diagnostic field trials) using clustering algorithm with expectation-maximization.

  1. Non-responsive soils that do not respond to fertilizers but to liming, micronutrients or manure application (37% of observations; first graph in Figure 1).
  2. Responsive soils that respond strongly to NPK application (20% of observations; second graph in Figure 1).
  3. An intermediate group that responds to N application (though not as strong as the responsive soils) and manure (43% of observations).

These results indicate that different types of soils have different responses to various fertilizers and other treatments. This important information will allow farmers, extension agents, and others to utilize the most appropriate type of fertilizer or treatment for their specific soil type. This not only helps farmers improve agricultural productivity but will greatly increase the efficiency of resource use, ensuring that money is not lost on inappropriate fertilizer type. Importantly, as well, such trials will help scientists determine management recommendations for non-responsive soils. Further studies will illustrate the distinctive soil properties that allow discrimination between the behavioral patterns of these soils and to what extent soil degradation has contributed to these high percentages of marginal and poor soils.

Submit Comment

Your email address will not be published. Required fields are marked *