I am usually taken aback when I see how our farmers are still so dependent on rain-fed agriculture. With climate change, clearly, it is unsustainable especially in arid and semi arid areas. Drylands are characterised by low and highly variable rainfall and this is the main challenge to rain-fed crop production.
Climate change is associated with increased rainfall variability and higher temperatures and reduces the water available for crop growth and development. To reduce the climate-related risks farmers relying purely on rainfall, need to know how to make the most use of the rainfall that they receive. This involves understanding when to plant, what to plant and how to manage the water throughout the growing season. Climate services for agriculture aim to provide climate information in a way that assists decision making by farmers, extension workers and other supportive organisations. Such services require appropriate engagement along with an effective access mechanism and must respond to user needs.
In Kenya we have mainly two seasons: the long rain season from March to May and the short rain season from October to November.
A timely start coupled with selection of the crop variety whose growing season length and water requirements fits within the anticipated season enhances the chances of a good yield. The average start of a season is known by many farmers from past experience. It can also be determined from analysis of past rainfall records. However, farmers need to understand the seasonal forecast information provided by the Kenya Meteorological Department ahead of each season as this often sheds more light into the expected amount of rainfall and length of the season. In spite of the farmers experience and the scientific knowledge that exists about weather and climate, climate related risks are inevitable and farmers in drylands need all the support available to manage these risks.
A timely start
To illustrate the kind of risks experienced, a good case study is Katumani in Machakos. The mean annual rainfall is 670 mm with 300 mm falling over the short rains of October, November and December (OND), 270 mm over March, April and May (MAM) and about 100 mm over the rest of the months.
The OND season is therefore more endowed with rain compared to the MAM season. The OND growing season starts on average 15th October and ends on December 30 thereby lasting 75 days.
The average seasonal rainfall over this period is 300 mm. However, only 40 per cent of the OND seasons receive 300 mm and above. A maize crop planted on October 15 that matures over 90 days under the climatic conditions of Katumani requires approximately 300 mm of rainfall.
That means for 60 per cent of the seasons, the rainfall will be less than what a maize crop that matures in 90 days requires. For crops planted around mid-October, the number of days to maturity is the major determinant of the crop water requirement. A crop that would mature in 75 days would need 250 mm and one takes in 60 days would need 200 mm.
The chance of getting at least 200 mm is 90 per cent and over 250 mm is 55 per cent. So selecting early maturing, high yielding varieties and being ready to plant as early as possible in the season is a good strategy to reduce water-related risks.
But that alone is not sufficient. Managing the rainfall and the soil so that infiltration is maximised, runoff is avoided, evaporation losses from exposed soil is minimised and making sure that the crop is disease-free and has all the nutrients required completes the package of practices that farmers need to reduce production risks. We see here that water is so limited and everything that one can do to make use of every drop is critical.
Get start of the season right
Coming in too early is not good; so if some rains appear in September, it might not be wise to rush to plant. Usually dry spells lasting over 10 days might follow and kill the young plants. From long term records of rainfall, the earliest start of the OND season is November 13. In 20 per cent of the OND seasons, (that is two times in ten years) the OND season fails to start within the months of November to December.
For half of the OND seasons, the start of season happens after November 30 and therefore the season ends up being too short for the most crops which require more than 60 days to mature. In addition, in Katumani, about 90 per cent of the rainfall received in a year evaporates back into the atmosphere due to the high temperatures.
This means that farmers have to practice water conservation to preserve water in the soil. Some practices that help conserve water include reduced tillage, cover crops, crop rotations, mulching, use of farm-yard manure, ridging, contour farming and pit-planting.
Understand local climate
Understanding the local climate and the water requirements of your crops needs is fundamental to water management in the drylands. In addition, farmers need to pay attention to the climate information issued by Kenya Meteorological Department (KMD).
With devolution, there is an officer from KMD stationed in each County headquarter. They are tasked with downscaling the national forecast to make it more relevant at the County level. However, forecasts are probabilistic and many farmers are disappointed when the outcome of a season does not look like what was forecast.
In the just completed OND 2018 season, the seasonal forecast issued by the Kenya Meteorological Department on 04/09/2018 predicted enhanced rainfall in many parts of Kenya.
[The writer is a Professor at Jomo Kenyatta University of Agriculture and Technology, a Climate Services Expert and PICSA Trainer and has worked in Eastern and Southern African countries]