By: Heidi Boening for the IAEA
Despite poor soil fertility and water scarcity, farmers in Kenya have increased their crop yields by 17-20% and saved 20% of their fertiliser costs thanks to climate-smart agricultural techniques
The techniques, introduced with the support of the International Atomic Energy Agency (IAEA), in partnership with the Food and Agriculture Organization of the United Nations (FAO), help improve soil fertility and enable farmers to better manage the crops’ water requirements.
Isotopic techniques play a crucial role in assessing nutrient qualities of soil and water resources. A group of scientists from the Kenya Agricultural and Livestock Research Organization (KALRO) used nuclear and isotopic techniques to measure changes in soil’s water and nutrients. This effort supports farming practices that keep the soil healthy, improve water and nutrient strategic use, optimise crop yields and increase soil resilience.
These techniques were used in the Kajiado-Central and Tharaka sub counties to assess crop nitrogen use efficiency and to calculate nutrient and water requirements using the stable isotope nitrogen-15 (N-15) and soil moisture sensors.
N-15 isotopes, which have the same amount of proton and electron as “normal” nitrogen atoms, but with an extra neutron, are effective tracers that can be employed to understand the movement of nutrients between soil and plants. They also help to provide quantitative data on the efficiency of nutrients use by crops and this data enables experts to improve water and fertiliser application strategies.
The nitrogen-15 tracing technique is also used to quantify the amount of nitrogen captured from the atmosphere through biological nitrogen fixation by leguminous crops — a natural process in which these crops capture nitrogen from the air and accumulate it in their roots. The nitrogen is released into the soil through the decay of plant roots after harvest, enhancing soil fertility. This technique reduces the need for expensive chemical fertilisers.
Intercropping and crop rotations of pearl millet and maize, the main crops in this region, with cowpea, beans, green gram, pigeon peas and other legumes not only saves the expense of nitrogen fertilisers, it also increased average yields by 20% for the cereals and by 17% for the legumes. “This was a win-win for farmers: reducing costs and achieving higher yields,” says Joseph Adu-Gyamfi, Integrated Soil Fertility Management Specialist at the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture.
Apart from the nutrients, farmers also need to ensure that the crops receive suitable soil moisture through supplementary irrigation when the rains fail. Scientists have installed soil sensors in selected farmers’ fields in several counties to measure real-time soil moisture, temperature and salinity. Once the soil moisture and related data collected is processed, the crop’s water requirements can be estimated, and farmers can be advised on irrigation strategies regarding quantity and frequency of watering. The real-time soil moisture measurements data is transmitted to farmers’ mobile phones, allowing them to determine when and how much to irrigate.
“KALRO scientists are now helping the farmers to source the seed, which they pay for by themselves,” says Isaya Sijali, Irrigation Specialist at the Food Crop Research Institute, KALRO-Kabete. This underscores the sustainability of the project: higher yield provides higher income, which enables farmers to pay for the improved seeds.
The IAEA, through its technical cooperation programme, has also supported the upgrade of KALRO’s analytical laboratory for agricultural water and nutrient management with the operationalisation of an existing Isotope Ratio Mass Spectrometer (IRMS) to meet the capacity for stable isotope analysis for nitrogen-15, the installation and training for a vacuum extraction of water from soil and plant samples for water isotopes analysis and the provision of a laser analyser for stable water isotope analysis of water. “The IAEA’s assistance in upgrading equipment has strengthened KALRO’s capability to hold national and regional trainings on water management and conduct stable isotope analysis of water and nutrients for neighbouring countries in the future,” says Valentina Varbanova, the IAEA Project Management Officer working with Kenya.
This article was first published by the International Atomic Energy Agency (IAEA)