Thursday, February 4, 2010

Lit in Review: Integrated Soil Fertility in Malawi

Sauer and Tchale (2009), "The Economics of Soil Fertility Management in Malawi," Review of Agricultural Economics, Vol. 31, No. 3, p. 535-560

Integrated Soil Fertility Management (ISFM) uses both organic and inorganic methods to improve soil quality, such as dual cropping complementary crops that can fertilize other and improved following. Sauer and Tchale (2009) review eight studies and produce another one demonstrating that ISFM provides greater productivity, profits, and sustainbility than chemical fertilizers alone for African smallholder farmers.

Maize yields in Malawi -- the subject of three of the case studies for our new Food Policy book: count em, one, two, three -- have been highly dependent on fertilizer prices and government policies. At the turn of the century, government policies had done a great deal to limit the growth of the private fertilizer market. Sauer and Tchale explain that "gertilizer dealers require substantial risk premiums to hold and transport fertilizer in an inflationary economy," and the increasing prices for fertilizer from reduced subsidies, devalued currency, and rising world prices have hurt demand for fertilizer greatly. So Integrated Soil Fertility Management (ISFM) is likely to do substantially better in Malawi relative to inorganic fertilizers only, than it would in other places.

In their study, they find that inorganic fertilizers have a return to scale of 0.5, compared with 2.5 for ISFM; ISFM improved maize yield by 8-9 percent in two areas and 3 percent in a third region. If you include the value of the other crops planted at the same time to fertilize the ground (groundnuts, soy, and pigeon peas), the yield increases. ISFM also significantly increases the marginal value of fertilizer. So supporting ISFM can reduce the government burden of fertilizer subsidies while increasing sustainability, incomes, and food security.


  1. Fertilizers in crops helps gain time factor and also increase the volume I know but what about the food quality?What about the soil that is left with residuals of fertilizers?Is it good for health?

  2. There are several dimensions of food quality. In terms of the qualities consumers tend to care about, fertilizers do a great job. In terms of health and food safety, fertilizers add nutrients that the plants would be taking from the soil in first place rather than adding new chemicals that would be harmful. Fertilizers do not harm food safety at all.

    Excessive or inappropriate timing of pesticide or fertilizer application can cause some problems, but in Malawi the concern isn't using too much but using far too little.

    Regarding soil fertility, part of the point of adding fertilizers to the soil is to improve fertility and soil health. The problem is that plants take nutrients out of the soil that are not replaced with some kind of fertilizer. Without fertilizers of some kind, soils become depleted and it can lead to desertification. Animal fertilizers are nice, but they cannot be balanced as precisely as chemical fertilizers can be for the particular soils and their particular needs -- though that is assuming a greater level of technical knowledge than is going to be available in many cases here. Other plant fertilizers are nice, but they require additional land to plant and time to harvest and apply. Integrated fertilization with legumes is quite promising, but legumes primarily add nitrogen, not the full complement of nutrients needed (I could be wrong on that last point).

    Is it good for health for people to starve because there isn't enough food locally? or for farming households to not have enough money to purchase additional foods because their land is not fertile? I don't think so.