Impact of Irrigation System on Microclimatic Parameters and Gas Exchange in Lowland Rice

Publikations-Art

Kongressbeitrag

Autoren

Stuerz, S. Sow, A., Asch, F.

Erscheinungsjahr

2012

Veröffentlicht in

Resilience of agricultural systems against crises

Herausgeber

Tielkes, E.

Verlag

DITSL GmbH , Witzenhausen

Seite (von - bis)

95

Tagungsname

Tropentag 2012

Tagungsort

Göttingen / Kassel

Interest in water-saving irrigation techniques in Senegal is rising from the aim toincrease the domestic rice production. Rice-rice double-cropping and expansion ofthe rice growing area are the strategies for becoming self-sufficient on rice in thenear future. Furthermore, high irrigation costs account for a relatively large shareof production expenses due to increasing fuel and electricity prices. Nevertheless,yield stability under water-saving irrigation is not assured and the reasons remainwidely unclear. In the absence of a ponded water layer, plants are exposed to highertemperature extremes at the growing point. In addition, reduced evaporation can leadto lower relative humidity in the canopy. Therefore, microclimate is considered toinfluence gas-exchange parameters.Experiments were conducted between November 2008 and October 2010 in Ndiaye,located in the Senegal River delta, with typical Sahelian climatic conditions and thusthree distinct seasons: a hot-dry-season from March to July, a short wet-season fromAugust to October and a cold-dry-season from November to February. In bi-monthlystaggered sowing dates, soil temperature, temperature at the growing point and insidethe canopy as well as relative humidity inside the canopy was observed for five ir-rigated lowland rice varieties grown under flooded and non-flooded conditions year-around. Gas-exchange measurements for transpiration, assimilation and stomatal con-ductance were conducted on a regular basis.The effect of higher temperature amplitude in the absence of a ponded water layerwas more pronounced in the two dry-seasons than in the wet season. A negativeeffect of water-saving irrigation on soil temperature, temperature at the growing pointand relative humidity and thus an increased vapour pressure deficit inside the canopywas observed under hot and dry conditions. Low soil temperature and high vapourpressure deficits were associated with a decrease in stomatal conductance and thusassimilation rate. Reduction of assimilation rate without standing water under highvapour pressure deficits was more distinct in varieties adapted to the wet tropics thanin local varieties, whereas neither an impact of irrigation technique nor variety couldbe detected in the wet-season.