Field level

For two crops, rice and maize, three adaptation strategies at field scale are explored that address a baseline strategy mainly relying on rain-fed agriculture. Two other adaptations focus on irrigated and intensified conditions. The adaptation strategy mentioned as intensification consists of a package of cultivation practices, which in general will increase crop yields, e.g. improved crop variety, denser planting, chemical inputs and shorter season. Since rice is grown in the wet period, it was explored what the result of growing rice under only rain-fed conditions would be. Irrigated rice was, therefore, the baseline. Rain-fed rice was one adaptation strategy and intensified rice production was the second strategy. Maize production during the wet season is normally done under rain-fed conditions and this practice is used here as the baseline. The adaptation strategies for maize were growing irrigated maize and growing maize with intensified cultivation practices.

Under the baseline - rain-fed - adaptation, rice yields increase slightly for the medium term (2010-2039) under Hadley A2. However, in the long term the yield experienced not only a decrease but also high variability. Under intensification in its

1961—1990 2010—2039 2070—2099

Fig. 9.8. Rice yield prediction under Hadley A2 for no irrigation and intensification.

Fig. 9.8. Rice yield prediction under Hadley A2 for no irrigation and intensification.

3000-

2000-

1000-

1000-

1961-1990 2010-2039 2070-2099

2000 J

2000 J

r

X

_

T

:

1

1

r

1961-1990 2010-2039 2070-2099

1961-1990 2010-2039 2070-2099

Fig. 9.9. Maize yield prediction under Hadley A2 for irrigation and crop intensification.

Table 9.5. Crop production under adaptation for maize and rice in tonnes.

Adaptation strategy 1961-1990 2010-2039 2070-2099

Rice No irrigation 40,216 53,196 39,830

Intensification 8,734 110,242 131,186

Maize Irrigation 1,186,680 1,192,973 131,186

Intensification 1,476,158 1,675,736 1,087,790

cultivation there is a dramatic increase in the yield both in the medium and long terms. Intensification here means: using improved seeds, good agronomic practices, good soil fertility and pest and diseases management but without irrigation (Fig. 9.8). Maize yield under Hadley A2 showed a modest increase with decrease in variability in the long term under irrigation. Under intensified production, however, there was a high variability in the yield, which slightly increases in the medium term and unexpectedly decreases in the long term (Fig. 9.9) (Table 9.5) (MWH, 2001).

Table 9.6. Impact matrix for the main adaptation strategies and the Hadley A2 scenarios.

Volta

Indicator

Unit

Future no Future no Current adaptation adaptation

1990

2030 A2

2070 A2

2030 Food

Adaptation

2070 Food

2030 Energy

2070 Energy

Environment Wetland loss

382,500

382,500

Food Energy

Rice Maize

Energy/year

Tonnes Tonnes TJoule

71,478 833,373 18,116

85,866 956,536 21,595

103,136 440,510 18,742

2,004,400 1,476,158 21,121

2,385,200 1,675,736 18,095

85,866 956,536 23,232

103,136 440,510 19,467

Low level

Years/30 years

CO UJ

0 0

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