Droughts

The just given mitigation approaches for temperature extremes are also successfully used in relatively short term drought conditions, although Walker (1991) believes that such chances are larger in Asia than in Africa. As an example of microclimate manipulation, Onyewotu et al. (2004) made understandable how multiple shelterbelts protected crops from advected hot dry air under conditions of limited water supply on soils reclaimed from desertification in Nigeria. As an example of crop selection, Das et al. (2003) give the case of using a perennial xerophyte cotton variety surviving drought with lower yields and compensating with good production in normal years.

An even more recent illustration was provided by H.P. Das (personal communication) for a prolonged dry period resulting in water deficiency in all the districts of Assam, India, from the 1st week of July up to the second week of August 2006, although the seasonal rainfall total had been forecasted as "normal" in that region. In fact a drought situation was declared by the state government. Along with this dry period, unusual high temperature was prevailing almost throughout the state. In view of this, farmers were advised to stop sowing "Sali" rice, as the delayed sowing of this would cause severe moisture stress in the plants, and to start sowing short duration pulses with minimum irrigation, ttey implemented the advice. Subsequently after onset of new rains, the farmers were advised to sow more pulses. tte state of the crops according to extension officers was satisfactory till the last date covered, by early September. It was noted that farmers are very conscious of their needs and appeared to be more interested in the onset of rains and dry spells. In this particular case, close monitoring of the rainfall situation rather than long range forecasts of the seasonal rainfall led to giving the right agrometeorological service, ttis illustrates the challenge of finding for each problem the simplest methods of support to mitigation possibilities instead of forcing methodologies to fit problem solving.

Although rainfall in Asia is generally expected by climate change scenarios to increase, the also increasing variability has already given yield diminishing moisture stresses due to prolonged dry spells in combination with heat stress (Zhao Yanxia et al. 2005). ttis makes the mitigation of, and for, dry spells the most challenging issue for the future. A culture of small scale water impoundment (Stigter et al. 2005a) may assist if the health dangers of standing water can be overcome.

0 0

Post a comment