SATrends Issue 91
June 2008
1. Underground agents survive the searing SAT

The earthworm is the farmer's friend. Its favorite food, plant matter, nourishes the soil after digestion. In an experiment at ICRISAT-Patancheru, ongoing since 1999, large numbers of earthworms were seen, especially in treatment plots where low-cost inputs, including weeds, glyricidia loppings and other plant materials are used.

HHB 67 Earthworms seen at ICRISAT-Patancheru

How do these creatures survive the temperatures at the height of a summer in the semi-arid tropics (SAT)? About 20 hours after a 36.7mm rainfall, and while assessing soil moisture before sowing, scientists noticed a high number of earthworms, and decided to quantify their population. Samples were taken from six different spots (treated as replications) from each of the four treatments. The highest population of worms was recorded in two treatments that haven't received any agro-chemicals and plowing since 1999 (labeled as Low cost 1 and 2 - LC1, LC2 in Table 1). The number of earthworms was at least 10 times higher than that in the control (Mainstream Agriculture - MA), and indicates the possible negative effects that fertilizers, pesticides and plowing used in the treatment have on earthworm populations.

The treatment ‘MA+Biomass’, which received both agrochemicals (as applied to MA) and biomass (at the rates similar to LC1 or LC2) also had a substantial population of earthworms, but was 38 to 40% lower than that in the LC1-LC2. This indicates that the possible negative effects of the agronomy in the MA were ameliorated by the added biomass.

HHB 67

Two types of full-grown worms (a) 3 to 5 cm long, and (b) 8 to 10 cm long were found. Both types are native to the soil and need to be identified. The big ones seem similar to Eisenia foetida. The small types were 7 to 15 times more in number than the big types. The fact that full-grown worms were observed in the topsoil within 20 hours and quantified within three days after the rain, suggests that large populations survive in depths lower than 60 cm in the soil profile, which may still be moist.

Details about this experiment are in: Rupela OP. 2008. Organic farming: Building on farmers' knowledge with modern science. Pages 28 to 45 in Organic farming in Rainfed Agriculture: Opportunities and Constraints (Venkateswarlu B, Balloli SS and Ramakrishna YS, eds.). Central Research Institute on Dryland Agriculture (CRIDA), Hyderabad.

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2. Livestock Water Productivity: Stimulating a new research agenda

The idea of more crop per drop has stimulated research and development to address water-use efficiency and increased production per unit area in cropping systems. Now that same concept of getting more per drop is being expanded to include livestock systems.

The livestock industry has often been criticized because vast amounts of water are needed to produce meat and milk. For example, much more water is needed to produce a kilogram of meat (13.5 m3) than a kilogram of vegetables (0.15 m3) or cereal (0.7-1.4 m3). As the pressure on livestock producers and governments to develop environmentally benign livestock systems mounts, it has become imperative to consider water-use efficiency in livestock systems.

HHB 67 Increasing the water-use efficiency at the farm level will create sustainable systems that avoid risk.

A team of scientists from IWMI, ICRISAT and ILRI together with their NARS partners in Ethiopia and Zimbabwe are studying opportunities to improve the water-use efficiency of crop-livestock systems as part of the BMZ-funded project Improving Water Productivity of Crop-Livestock Systems of Sub-Saharan Africa. Since livestock eat as much as 100 times more water than they drink, much of the research is focused on improving livestock management and feeding systems. The team has identified four main research areas:

The researchers will identify entry points to increase the water-use efficiency at the farm level focusing on livestock products in particular. In so doing, the project will identify the most efficient rather than the most productive systems. Efficient systems are more risk averse and sustainable, especially when allowing farmers to respond to the vagaries of climate change.

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