SATrends Issue 14 

January 2002

NEWS FROM THE DRY TROPICS:

  1. Back to the Drawing Board
  2. Weed Better, Weed Faster
  3. With Minds of their Own!
  4. Closing Ranks against the Pod Borer
  5. Highlights of Previous Issues

1. Back to the Drawing Board

Everyone hates dead-ends. But when you find yourself in one, you just curse your luck, backtrack, and take another road. In research, however, it's not all that simple, as the sorghum scientists based in Mali discovered when they came up against a major hurdle: the improved sorghum varieties that had been painstakingly developed over several years found few takers. Yet these were far more productive than the traditional varieties!

To solve the riddle, the scientists had to figure out what was wrong, and chart a new course, using a strategy that has never been tried before on graminaceous plants. If their strategy succeeds, "it could lead to a breakthrough for sorghum grain production in the West Africa savanna region," says Dr B Clerget, a plant physiologist from CIRAD (Centre de coopération internationale en recherche agronomique pour le développement), who is working with ICRISAT sorghum breeders on this problem in Mali.

"Improved sorghum varieties lack a fundamental trait of the local ecotype : sensitivity to daylength. This trait allows the local varieties to adjust their growth duration to the unpredictable rainy season of the Sahel," Dr Clerget explains. Photoperiodism is the process by which plants react to the length of lighting they receive.

Ironically, in eliminating this trait from improved varieties, the scientists had followed the Green Revolution strategy, which is based on the use of cultivars insensitive to photoperiodism for greater geographic adaptability. Little did the scientists know that this strategy would fail them in the West Africa savanna region.

In other words, although the local varieties are less productive, they are much better adapted to the region than the improved varieties. Thanks to their photoperiod-sensitivity, farmers can sow them early after the first rain, irrespective of when it occurs. This helps the plants to compete against weeds and benefit from the quick nitrogen mineralization process that occurs during this period. The plants reach flowering at a fix date close to the end of rainy season and produce grain, avoiding attacks from insects, birds, and grain mold.

Now that the scientists have figured out what went wrong, they are developing new varieties, keeping the photoperiod-sensitivity trait of the local types, while making them more productive. New tools, such as modeling, are helping them to understand better the effects of variable growth duration on the plant architecture.

Looks like dead-ends are quite useful for research.

For more information, contact b.clerget@icrisatml.org

Top

 

2. Weed Better, Weed Faster

Smallholder farming is hard work, quite literally. The greatest demands for mechanical energy are for land preparation and weed control; either or both of these can cause bottlenecks and reduce productivity and output.

For land preparation, the limit is due primarily to the intensity of energy demand. For weed control, the duration of the demand is likely to be more restricting. The maximum rate of work (i.e., power developed) a smallholder can generate is around 40 watts over a 6-hour working day and this energy (totalling around 0.9 MJ) is applied rather inefficiently when simple hand tools – typically hoes of various designs – are used. Although weeding requires less power than land preparation, it has to be completed within a short period. This contributes to the drudgery of long hours of weeding, a burden borne mainly by women who must combine weeding with their domestic tasks.

Animal-drawn weeding implements are far more efficient. A range of equipment is available, but farmers and extension agents lack technical information on their performance. Recent work by ICRISAT and its partners – the Zimbabwean Institute for Agricultural Engineering and the Silsoe Research Institute, UK – examined the performance of a range of animal-drawn weeders and weeding practices common in southern Africa.

Results for two different soil types, albeit for a wetter than average season, have helped clarify some of the reasons why many farmers are unwilling to use the traditional five-tine weeder, even after they have bought one. In terms of weeding efficiency, the light three-tined cultivator is very similar to the traditional five-tined cultivator but it has a lower work rate and is more difficult to control on heavier soils, particularly when the reversible tines are replaced with the ducks foot type.

For heavier soils, farmers should use the reversible tines that are sold with most cultivators. On lighter sandy soils, ducks foot tines are recommended. For farmers who own draft animals but do not own a cultivator, a good alternative is post-emergent ridge weeding using a moldboard plough. This not only gives good weed control, but also increases crop yields. Productivity can be further enhanced by tying the ridges to conserve moisture.

For more information, contact s.twomlow@cgiar.org

Top

 

3. With Minds of their Own!

It all started in 1993 when the Southern African Development Community (SADC) Groundnut Project (supported by BMZ-GTZ), based at the Chitedze Research Station in Lilongwe, Malawi invited 300 women farmers from the surrounding districts to a field day. At the end of the day farmers were given 1-kg groundnut seed for planting in group-fields. The objective was to establish demonstration plots for their groups according to specifications they had learned that day.

The crops performed very well the following season and most farmers were keen to acquire more seed to establish individual plots this time. However, some officials advised the farmers to consume whatever they harvested and not keep the seed. The reason? "Because the lines were not yet officially released for cultivation." A few of the older women with minds of their own disregarded the advice and kept seed of their favorite lines. These wily women then planted the seed every year, and gifted small quantities of this treasure to close relatives.

On one occasion, ICRISAT scientists ran into one of these old women farmers. She had almost a hectare of the improved high yielding ICGV-SM 83078 (CG 7 or MGV 4) planted in neatly-weeded rows. She and her husband had been growing the variety for 5 years, gradually increasing the acreage of their field. She too had been gifting seed to her close relatives every year. One of the recipients in 1999 was her young daughter-in-law (in the picture with a baby).

On the road to Chitedze is a large commercial farm where CG 7 has been established at optimum recommended agronomic practices. The SADC/ICRISAT Groundnut Project scientists believe that the task of minimizing the existing gap between the smallholder farmer and the large commercial farmer is achievable with a little improvement.

Smallholder farmers participating in the Project work have agreed to make this possible by increasing the plant density through row spacing adjustments. This will suppress weeds, save labor, and release land for other crops. And it all started because a few women had the courage of their convictions.

For more information, contact e.minja@cgiar.org or p.vandermerwe@cgiar.org

Top

4. Closing Ranks against the Pod Borer

The Helicoverpa pod borer causes an estimated loss of over $900 million in pigeonpea and chickpea in the semi-arid tropics, and possibly over $2,000 million worldwide. An estimated $1,000 million are spent on pesticides to control this pest. In addition to huge direct economic costs, the indirect costs flowing from the deleterious effects of pesticides on the environment and human health are increasingly unacceptable to people everywhere. For problems as intractable as Helicoverpa, scientists believe that no single strategy will suffice to contain this pest. Environmentally safe technologies are not yet ready in a form to be delivered to the farmers.

A 2-day workshop was held at ICRISAT in December 2001 to discuss "Helicoverpa Management - The Journey Ahead". The workshop was organized to:

  •  Document the progress made in Helicoverpa management
  •  Assess the potential of different pest management practices and identify the bottlenecks
  •  Explore the potential of biotechnological tools for Helicoverpa management
  •  Identify priorities for future research in Helicoverpa management

Twenty papers covering biology and population dynamics, host plant resistance, biotechnological approaches, management practices, and integrated pest management were presented during the workshop. The workshop deliberations focused on:

  •  Analysis of multitrophic interactions in the context of crop production and environment conservation.
  •  Effective integration of agronomic practices, host plant resistance, natural enemies, and natural pesticides.
  •  Exploring the possibilities of maximizing the efficacy of insecticide use, while minimizing harmful effects on the environment.
  •  Developing a comprehensive module for Helicoverpa management in different crops and cropping systems.

Over 60 scientists from several organization (including the Indian Council of Agricultural Research; Agricultural Universities; Private Industry; Council of Scientific and Industrial Research; Natural Resources Institute, UK; University of Sydney; and Commonwealth Scientific and Industrial Research Organization, Australia), and 20 scientists/students from ICRISAT participated in the event.

For more information, contact h.sharma@cgiar.org

Top