Fertigation - the importance of water and nutrients to food production

Plants need water and nutrients – so why not to combine the application of both. Such a combination is called fertigation; it applies nutrients together with the irrigation water.

Scarcity of water in good quality is becoming a major concern in the world. Agriculture is the largest user of water, and has the target to enhance water-use-efficiency. Fertigation technology allows a better use of water. Micro-irrigation systems as drip irrigation (photo 1), have been developed, and provide a better water-use-efficiency of between 80 to 90 %, while other irrigation practices only have a 40-50 % water-use-efficiency. Drip irrigation places the water close to the roots. This reduces the volume of watered soil and the water loss by evaporation. In the past 20 years, the acreage under drip irrigation has grown from 0.4 million ha in the early eighties to up to 3 million ha in the late nineties. The anticipated growth in years to come is estimated to be 6-12%/year.

Drip irrigation system

Once a drip irrigation system is established, it invites to be used not only for irrigation, but also for fertigation, as fertilizers can be easily dissolved in a tank with water prior to application, and injected into the irrigation water according to crop demand.

 The shift from “traditional fertilizer practice” of solid fertilizers to fertigation requires different technical know how and different types of fertilizers. Micro-irrigation systems are sensitive to clogging, therefore mineral particles e.g. from incomplete dissolving fertilizers, precipitation or microbial growth have to be avoided and the fertilizers, either in solid or liquid form as straights or ready-made mixtures have to be completely water soluble.

In drip irrigation systems the soil volume in which the roots grow will be reduced to the soil volume that is watered. A high root density is found in these fertigation bulbs and it is crucial to ensure optimum growth conditions in terms of nutrient and water supply. In order to avoid salinity problems, fertigation should use fertilizers, like calcium nitrate or potassium nitrate, which do not contain any other elements that are not necessary for the nutrition of the crop.

With fertigation, highly plant available nutrients can be placed close to the roots in required rates when needed. As crops require different rates of each nutrient at specific physiological growth stages, fertigation enables the grower to increase yield and fine tune quality of the crop and to strongly enhance fertilizer-use-efficiency (figure 1).

Figure 1: Fertigation increases yield and water-use-efficiency.

The yield increase in fertigation systems is in line with the need to intensify land-use-efficiency to meet the food demand of the growing population by production on a shrinking acreage of available arable land. Furthermore, the higher nutrient-use-efficiency is of advantage for the environment, as nutrients used by the crop are not lost by leaching or gaseous losses.

Fertigation opens new opportunities to optimize plant nutrition, and Yara is investing in research to optimize fertigation recommendations and to improve the understanding of the nutrient dynamics in fertigation systems. Furthermore it is developing tools to improve the nutrient management in fertigation systems, like the computer programme FAST. Trials are showing that calcium nitrate provides a soluble Ca source, which is quite mobile in soil (figure 2).

Figure 2: Water and nutrient distribution in the wetted zone.

Furthermore, it was found that calcium nitrate in combination with potassium nitrate can ameliorate stress caused e.g. by salinity (figure 3).

Figure 3: Calcinit increase yield and quality under saline growing conditions.

Together with our alliance partners SQM, Phosyn and Akzo Nobel, Yara offers the whole range of highly water-soluble fertilizers and additives, which fits best in fertigation systems.