While 2 litres of water are often sufficient for daily drinking purposes, it takes about 3,000 litres to produce the daily food needs of a person. To grow one apple we need 70 litres of water, 1 slice of bread is 40 litres, and 1 steak more than 2,000 litres. Everything that we eat or waste, needs water to grow. Globally, the agricultural sector consumes about 70% of the planet’s accessible freshwater, more than twice that of industry (20%) and municipal use (10%).
But water alone is not sufficient to grow or sustain plant growth without soil nutrients and vice versa. Plant nutrients and water are complementary inputs, and plant growth responds according to the availability of them. For example, the processes of nutrient accumulation or depletion are often related to transport processes in water.
The International Fertilizer Industry Association (IFA), the International Water Management Institute (IWMI), the International Plant Nutrition Institute (IPNI) and the International Potash Institute (IPI) jointly published a reference guide, Managing Water and Fertilizer for Sustainable Agricultural Intensification (PDF 15.1MB), to improve general understanding of the best management practices for the use of water and fertilizers throughout the world. Sustainable management of these resources will allow farmers to achieve higher yields and better returns, while mitigating possible negative environmental impacts of their activity.
According with this guide, the interaction of water and nutrients in soil fertility management is governed by the following considerations:
- Soil water stress will limit soil nutrient use at the plant level.
- Soil-supplied nutrients can be taken up by plants only when sufficient soil solution allows mass flow and diffusion of nutrients to roots.
- Soil water content is the single most important factor controlling the rate of many chemical and biological processes, which influence nutrient availability.
Farmers must manage both inputs very closely to ensure they achieve high yields and obtain good returns on their investments. A plant with adequate nutrition is more resistant to water stress conditions. This is particularly important considering the increasing water scarcity throughout the world. The book anticipates that severe scarcity is anticipated in the breadbaskets of northwest India and northern China, and most small islands in the Caribbean and Pacific regions will face increasing water shortage in future.
Although global fertilizer demand is expected to continue increasing, there are still large areas where farmers use little fertilizer and mine their soil nutrient reserves. In 2013, sub-Saharan Africa farmers are estimated to have used only 10% of the global average of fertilizers.
The book calls for a change in approach to address the interactions between water productivity and nutrient use efficiency in irrigated and rain-fed conditions. It also highlights that innovation in water and plant nutrients management, along with policy reform and incentive-based approaches will be critical in this process.
This book is a timely and valuable contribution to expand and transfer the knowledge on plant nutrition and water management and the challenges we face in achieving the Sustainable Development Goals. You can download Managing Water and Fertilizer for Sustainable Agricultural Intensification (PDF 15.1MB) here.