Use of Aquacrop Model to Predict Maize Yields under Depleted Rainfall and Elevated Temperature in a Semi-Arid Environment in Kenya
Volume 6:3
Joab Onyango Wamari*, Sijali Vincent Isaya*,Lee Heng Kheng**, Joseph Mutwiri Miriti***, Esilaba Anthony Obutiati****
*Kenya Agricultural Research Laboratories-Kenya, **Soil and Water management and Crop Nutrition Section, ***National Agricultural Research Centre -Kenya, ****Kenya Agricultural Research institute
Joab Onyango Wamari
Kenya Agricultural Research Laboratories
P. O. Box 14733-00800, Nairobi Kenya.
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(Manuscript received 22 June 2011, in final form 11 January 2012)
There has been increasing concern that drier and hotter seasons are becoming more frequent due to climate change especially in semi-arid environments causing adverse effects on agricultural production. Analysis of long-term (1980-2010) trends of rainfall in the first growing season (i.e. March and July) at Katumani, Kenya showed that about 55% of the seasons were below the long-term average, with an all time low occurring in the year 2000. Although the wettest years (1998 and 1985 ) had relatively
higher percentages above the long-term average (143.9% and 138.4% ) compared to lower percentages ( 61.7% and 59.7%) of the driest years ( 2000 and 1987), the latter were relatively less in numbers (i.e. 45%). Mean seasonal temperatures however did not show high variation from the long term mean implying that rainfall was the main cause of yield variation in this area. The AquaCrop model (Ver. 3.1) evaluated using three years (i.e. 1999, 2000 and 2001) of experimental results at Katumani, gave reasonable estimates of above ground biomass and grain yield of Katumani composite maize variety. The model was then used to predict Katumani maize yields under 20% depletion of rainfall and 3°C temperature elevation scenarios. Biomass and grain yields simulated respectively ranged between 2.971 to 6.558 and 0.910 to 2.564 T Ha-1 with probabilities of obtaining 3-5 T Ha-1 biomass and 1-2 T Ha-1 grain yields each dropping from 98 to 25%. Adaptation measures are given as management recommendations in line with the changed climatic scenario.
Keywords: Katumani maize composite, AquaCrop model, Semi-arid environment. Kenya
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