Conventional water management was by furrow irrigation or flood irrigation some fifty odd years ago. Today it may be largely using drip system. But these are merely different forms of irrigation that have their own advantages and disadvantages on the basis of managing water stress, nutrient uptake, and application of chemical fertilizers. But still the irrigation system does not mean water management.
Plants don’t need water. They need enough moisture in the soil. They need proper composition of soil, water and air in the root zone. Often farmer uses excess water. This chokes the plants, builds disease causing microbes and reduces the yield. We must understand water requirement and water stress. We must also consider quality of water. Then only we will be able to do proper water management. Role of organic matter in this is immense.
A water budget should be used to track water entering and leaving the system. In a water budget, the crop root zone is visualized as a reservoir of available water. The reservoir is built by rainfall and irrigation. Water is removed from the reservoir through crop water consumption – mainly evapotranspiration. Available soil moisture stored in the root zone represents the balance.
The lowest moisture level at which plant roots are able to extract moisture from the soil (before they wilt beyond recovery) is called the “permanent wilting point.” Just above this point the plants experience tolerable water stress. The highest moisture level that a soil can hold against gravity (when the excess has drained after saturation) is called “field capacity.” Field capacity is determined by soil type, but by and large influenced by the available organic matter. Inorganic soil is just like a heap of pebbles. It can retain water only be surface tension between two pebble surfaces. Organic matter is like a sponge. It can hold much more water than that held by the surface tension.
The farmer needs all this knowledge converted in to applicable methodology. Just testing soil moisture, air temperature and leaf temperature can give you meaningful information of the sufficiency of water applied; provided you know the stage of crop and irrigation schedule followed. Doing this can solve the problem precisely at the micro level. But we keep on discussing soil types and their water retention capacity, evapotranspiration rate of plants; which farmers are not able to use.
Farmers must be educated that excess use of water is always bad. Slight deficit is advisable. Such principles with simple analysis tools to guide about the sufficiency of water used will allow the farmers to achieve proper water management through their conventional irrigation system. They will understand importance of organic matter. They will understand that water application and nutrient uptake may not have any correlation. They will then be empowered to make judicial use of chemical fertilizers, and will focus on water quality, and management.