Preface Fertigation requires a thorough understanding of the science behind the technology to make it deliver the immense possibility it offers in crop production. Though the idea of fertigation existed from the times of solution culture, it did not receive the necessary attention from among plant nutritionists and agronomists when it reappeared in the context of micro irrigation. Fertilizer application in field agriculture has also not developed as a precision technology. Recommendations of the quantum of fertilizers required for a crop, at least in India are not based on current varieties of the crops, nor have they anything to do with the growth rate and developmental changes occurring while a crop is managed by the grower. Most of the fertilizer recommendations are itself very old and efforts to make them relevant to the current growing conditions, soil status, crop variety and crops reaction to the environment etc. are very limited. It is even worse when growers follow traders’ recommendations whose idea is to sell more the fertilizer they supply. Not only lower yields and very low fertilizer use efficiencies, but the deterioration of soil and water bodies are the results. In this scenario, a good knowledge of fertigation; its principle, process and field level application is critical to get more crop per unit nutrient; higher fertilizer use efficiencies. It is essential to confirm fertigation schedules at the field level by regular and repeatable agronomy trials in the field. Unfortunately, almost all the trials so far concentrated only on testing the total amount of fertilizer for a crop when fertigated vis-a-vis soil applied. While it is important to quantify the crop requirement of fertilizers, it is equally important to figure out the time a particular nutrient to be introduced in fertigation in order to get the best effects of nutrient on crop yield and quality. More research in this area is required before standardized fertigation plans (or programs) for many crops are designed and recommended to the growers. It is also necessary to introduce Fertigation as a major subject at the University level or even earlier in the academic curricula. In this book, I try to explain the basics and project the future course this technology may take in assisting precision crop production. A lot ofthe analysis is based on direct field experience of last 3 decades of extension and farmer support programs conducted by the author along with a team he developed, among small land holder farmers in several states in India and countries overseas. The author extends a very deep gratitude to Jain Irrigation Systems Ltd., a company which acted as the backbone of introducing micro irrigation and fertigation to Indian farmers with a very practical approach- Research, Develop, and Demonstrate in house and Train the farmers throughout the crop cycle, so that they ultimately become field masters of the technology. They saw, they were Taught, and they Applied their learning and they Won. This is continuing in the farm.

What is that the grower wants to achieve while he nourishes the crop with costly fertilizer inputs? He would like to get maximum output (yield and quality) of the produce; and for the maximization of out-put the fertilizer input should be utilized by the crop to its maximum potential. Thus it is not higher fertilizer dose that decides the highest yield; but the highest efficiency in crop’s use of those fertilizers. The efficiency, yield/unit fertilizer can be enhanced by the following factors; a) Plant roots absorbing (in-take) total quanta of applied fertilizer and minimizing the loss of applied nutrients by not having spare quantities lying around the soil profile. This is possible only if the quantum of application matches with the quantum of need. b) Plants utilizing the absorbed nutrients for metabolic activities concurrent to absorption. This is possible only if the fertilizers are applied in times of need of the plants and not before or after. This compels the grower to know the physiological need of the nutrient during each developmental stages; which nutrient required when. Here the grower must have a powerful tool or method to provide nutrients to the plants strictly following the above two factors. Fertigation offers an opportunity to practice nutrient inputs based on the above two factors: the grower is able to correctly decide the dose, type and time of providing the correct nutrient at precise quantity and at the required stage of plant/ crop development. Thus the purpose of Agriculture, to maximize yield and quality of crops and minimize the costs of production while maintaining sustainability can be put into practice by fertigation. Two most important prerequisites to achieve all of these are the optimal and balanced supply of water and nutrients. Tuning of plant nutrient supply with the uptake and utilization rates by crops is essentially an art and is made doable by fertigation technology.

Only a very brief mention of various basic aspects of plant nutrition is given here. Associates wanting to know more details should refer to any one of the standard Plant Nutrition publication (PRINCIPLES OF PLANT NUTRITION by K. Mengel and E.A. Kirkby). Increased production of food and cash crops is the need of our times; as land and irrigation water are limited and beyond any means of expansion. Crop yields per unit input should increase. Crop yield under natural production systems is limited by the availability of nutrients in the soil. Unless the supply of nutrients can be enhanced yields cannot be high.

Although the application of fertilizer to even fairly fertile soils can give a great increase in crop yield, soil fertility is not simply a matter of nutrient content. It is dependent on a number of complex of issues: Soil depth The volume of soil from which the crop draws its nutrition varies according to the rooting depth of the crop. However hard or rocky layers can restrict natural root development; this is particularly the case with micro irrigation systems. Soil structure Particle size and soil aggregate size and distribution, effect the size and distribution of pores and therefore the availability of air and water to the roots.

Organic Fertilizers and Manures Farmers have been using organic waste as fertilizers for a very long time. As previously mentioned, the application of O.M. to a soil can have number of beneficial effects on soil structure, C.E.C. and microbial activity. However, organic manures mainly originate from the waste products of animal and plant production and although rich in carbon compounds, they are usually relatively poor in available plant nutrients. The nutrient content of organic manures varies widely depending on their source and moisture content. Farm yard manure (F.Y.M.) is one of the most common organic fertilizers used. Others are concentrated animal manures, and crop residues such as straw.

There is a lot of confusion and lack of understanding when it comes to scheduling of fertigation. Even crop specialists prepare a fertigation dosage by dividing the total fertilizer quantity by the number of days of crop growth. This is highly erroneous. A scientifically prepared fertigation plan allows coordination of nutrient supply with changing demands of the growing crops which changes with the physiological shifts in the crop. Fertigation planner requires following information to prepare this schedule- which, when and how much plan:

The crop growing environment, both soil/media and aerial are controlled in green house. Therefore, the movement of water (liquid and vapour) and minerals (nutrient ions) follow a different pattern altogether. This factor should be considered while preparing the fertigation program. This becomes all the more different if soil-less rooting media is used. Table 7.1: Differences in Nutrient uptake in open field and Protected (GH) conditions.

Fig 8.1: A scheme for fertigation program working with automation In modern farming with fertigation machines (NutriCare) and automated drip irrigation systems, fertigation set up schemes like the above are put into practice. This scheme will stream line the installation, operation and monitoring of the entire process. An informed grower would be able to control crop performance more precisely and achieve his objectives.

References 1. Kafkafi. U and J. Tarchitsky. 2011 Fertigation -A tool for efficient fertilizer and water management. International Fertilizer Industry Association (IFA) and International Potash Institute (IPI). Paris, France. 2. Mengel .K, and E.A.Kirkby, 2001. Principles of Plant Nutrition. 5th edition. Dordrecht: Kluwer Academic Publishers. 3. Ankerman. B.S, and Large .R., (Ed.) 2005 Soil and Plant analysis Agronomy Handbook. A & L Agricultural Laboratories. 4. Soils Bulletin 1980. Soils and Plant testing as a basis of Fertilizer recommendations. FAO bulletins. FAO portal. 5. Zende, G.K., 1984. Efficient use of fertilizers for increasing sugarcane productivity. 34th Convention of DSTA, Pune, India. 6. Hoagland, D.R. and D.I. Arnon, 1950. The water culture method for growing plants without soil. Circular, California Agriculture Experiment Station. Vol. 347 (2nd Ed.). 7. International Potash Institute (IPI) 2005. Fertigation Proceedings: Selected papers on the IPI-NATESC-CAU-CAAS International Symposium on Fertigation, (ed. P. Imas and M.R. Price), Beijing, China, 20-24 September 2005.