Its a very pertinent issue Dr Shirgure , you have raised.  Efficiency of applied nutrients is only possible when associated with optimum irrigation , as part of fertigation . But , the efficacy of fertigation can further be expanded through variable rate application , in order to rationalise the use effiicency of both water and fertilizers. I agree with Dr Prem Baboo.  Using this concept , the Open Filed Hydroponics  in perennial crops started in countries Argentina, Australia, South Africa . To your surprise , it is a huge success . so day -by-day , fertigation is assuming greater significance in fruits and vegetables , in addition to  Floriculture under protected cultivation . 

In a recent study, tree canopy sizes ranging from 0 to 240 m3 were measured with an ultrasonic sensor system in a 17-ha ‘Valencia’ orange  were applied with a VRF spreader according to a prescription map developed from tree canopy size information. For comparison, half of the orchard received the standard uniform N rate of 269 kg·ha−1 per year. Soil leachate samples were collected with vacuum lysimeters at 1.5-m soil depth from below the root zones of 36 trees in 18 paired plots. The leachate samples from 10 sampling dates in 2005 were analyzed for nitrate-N concentration, and leaf samples were analyzed for leaf nutrient concentrations under VRF and uniform fertilization. Trees with excess leaf N (>3%) under uniform fertilization all had smaller canopy volumes (less than 100 m3), and constituted 62% of the orchard. This was evidence of excess fertilization under uniform fertilization management. In contrast, the VRF treatment significantly (P ≤ 0.05) decreased nitrate loading from leachates leaving the root zone compared with the uniform treatment. Mean leachate nitrate-N concentrations for all VRF treatments ranged from 1.5 to 4.5 mg·L−1and were below the maximum contaminant level for groundwater of 10 mg·L−1, while those under uniformly fertilized small and large trees were 28.5 and 14.0 mg·L−1, respectively

Crop canopy quality data from new sensors, in addition to canopy size, would be valuable to distinguish between healthy living and diseased or dead plants. Weak, sick, or dead plants that will not recover should not be fertilized because the nutrients will not be used efficiently in the root zone. Existing canopy sensors tend to measure only size, and can therefore not discriminate between healthy or dead plants.

The competition for existing freshwater supplies will require a paradigmatic shift from maximizing productivity per unit of land area to maximizing productivity per unit of water consumed. This shift will, in turn, demand broad systems approaches that physically and biologically optimize irrigation relative to water delivery and application schemes, rainfall, critical growth stages, soil fertility, location, and weather. Water can be conserved at a watershed or regional level for other uses only if evaporation, transpiration, or both are reduced and unrecoverable losses to unusable sinks are minimized (e.g., salty groundwater or oceans). Agricultural advances will include implementation of crop location strategies, conversion to crops with higher economic value or productivity per unit of water consumed, and adoption of alternate drought-tolerant crops. Emerging computerized GPS-based precision irrigation technologies for self-propelled sprinklers and microirrigation systems will enable growers to apply water and agrochemicals more precisely and site specifically to match soil and plant status and needs as provided by wireless sensor networks. Agriculturalists will need to exercise flexibility in managing the rate, frequency, and duration of water supplies to successfully allocate limited water and other inputs to fruits tree. The most effective means to conserve water appears to be through carefully managed deficit irrigation strategies that are supported by advanced irrigation system and flexible, state-of-the-art water delivery systems. Nonagricultural water users will need to exercise patience as tools reflecting the paradigmatic shift are actualized. Both groups will need to cooperate and compromise as they practice more conservative approaches to freshwater consumption.

Proper nutrition is essential for satisfactory crop growth and production. The use of soil tests can help to determine the status of plant available nutrients to develop fertilizer recommendations to achieve optimum crop production. The profit potential for farmers depends on producing enough crops per acre to keep production costs below the selling price. Efficient application of the correct types and amounts of fertilizers for the supply of the nutrients is an important part of achieving profitable yields. When an essential element is at a low concentration that severely limits yield and produces more or less distinct deficiency symptoms. Extreme deficiencies will lead to death of the plant. When the level of an essential plant nutrient is below that required for optimum yields or when there is an imbalance with another nutrient. Symptoms of this condition are seldom evident. When the concentration of an essential nutrient is present in adequate amounts for optimum crop growth. When the concentration of an essential plant nutrient is sufficiently high to result in a corresponding shortage of another nutrient. A major problem in appropriate fertilizer use is an imbalance of applied nutrients. Nitrogen applications tend to be much too high in relation to the amount of potassium and phosphate used. This is partly the result of price differentials, and partly the lack of knowledge among farmers about the need for balanced fertilizer applications.

Thanks Dr Prem Baboo. Nice information for further insight.

Its a very pertinent issue Dr Shirgure , you have raised.  Efficiency of applied nutrients is only possible when associated with optimum irrigation , as part of fertigation . But , the efficacy of fertigation can further be expanded through variable rate application , in order to rationalise the use effiicency of both water and fertilizers. I agree with Dr Prem Baboo.  Using this concept , the Open Filed Hydroponics  in perennial crops started in countries Argentina, Australia, South Africa . To your surprise , it is a huge success . so day -by-day , fertigation is assuming greater significance in fruits and vegetables , in addition to  Floriculture under protected cultivation . 

Thanks Dr Srivastava, you correctly stated about the importance and efficacy of the combined use of water and fertilizer inputs for the production of fruits and vegetables as well. This will help in refining the technologies further. 

Dr Shirgure , perhaps the most missing link in the whole issue that you have raised , i find , complete lack of information on the differential requirements of nutrients and water at different critical growth stages of different annual as well as perennial crops. This will lay the very solid foundation for joint use of irrigation and nutrients .

Fertilizer and water use efficiency must always be coupled, as all of you say. Just to add a new article published recently in Global Food Security, a JCR journal but focused on integrated knowledge. I hope you like it.

http://www.sciencedirect.com/science/article/pii/S2211912416300232

Yes, I like your link which enclosed. This is very useful information for all of us on the topic of integrated nutrient and water management. 

Dr Shirgure , it is equally important that a robust and dynamic basis of regulating irrigation is considered . Do you feel , which is the best method to base your irrigation treatments..?

Here are a few publications and presentations demonstrating differential rates of applied water based on crop ET.  We are now examining the impact of coupling Irr. and nutrient applications can further improve efficiency and yield outcomes.  Please send me a PM for additional detail.  

http://cemonterey.ucanr.edu/files/183679.pdf

http://cemonterey.ucanr.edu/about/contact/?facultyid=285

Johnson, L., M. Cahn, F. Martin, F. Melton, C. Lund, B. Farrara, and S. Benzen, 2014.

Results from 2012-2013 Salinas irrigation trials – further development of decision supporttools for cool season vegetable production. Proceedings, US Committee on Irrigation & Drainage, Water Management Conference, 4-7 March, Sacramento.

 Soil properties,soil water, soil air, fertilizer, crop genetic potential, weather, pest and disease incidence, weeds,duration, spacing, sowing time and other agronomic practices interact among themselves to influence the crop yield ultimately and it is virtually impossible to draw valid and time independent conclusions on the crop performance. The question posed by Dr. Parameshwar is next to impossible to provide answer which has universal application and reliability because of extremely complex interactions that operate at a given time. After all, we are dealing with a complex heterogenous soil system. Whereas in pure sciences such as chemistry it is possible to obtain repeatable and reproducible results as experimental conditions can be controlled such as pressure, temperature, volume, density, composition etc. 

Nice feedback by Kirk . Water application based on crop ET is usable even by the farmers as well . Soil tensiometers are considered very handy in regulating the time of irrigation . What are the options, farmers do have  or regulating the time and amount of water given to different crops. 

Let me  raise another issue in connection with on-going discussion . how can we monitor the rationale distribution of nutrients and water in different simulation zones identified in a given field , irrespective of method of application .   

 In 1804, Nicolas De Saussure proposed and published, results of his investigations that plants are composed of mineral and chemical elements obtained from water, soil and air. By 1842 a list of nine elements believed to be essential to plant growth had been made out. In his experiments with inert growing media. By feeding plants with water solutions of various combinations of soil elements growing in pure sand, quartz and charcoal (an inert medium not soil), to which were added solutions of known chemical composition. He concluded that water was essential for plant growth in providing hydrogen and that plant dry matter consisted of hydrogen plus carbon and oxygen which came from the air. He also stated that plants contain nitrogen and other mineral elements, and derive all of their nutrient requirements from the soil elements he used, he was then able to identify the mineral elements and what proportions were necessary to optimize plant growth, which was a major breakthrough.

In 1856 Salm-Horsmar developed techniques using sand and other inert media, various research workers had demonstrated by that time that plants could be grown in an inert medium moistened with a water solution containing minerals required by the plants. The next step was to eliminate the medium entirely and grow the plants in a water solution containing these minerals.

From discoveries and developments in the years 1859-1865 this technique was accomplished by two German scientists, Julius von Sachs (1860), professor of Botany at the University of Wurzburg (1832-1897), and W. Knop (1861), an agricultural chemist. Knop has been called "The Father of Water Culture".

In that same year (1860), Professor Julius von Sachs published the first standard formula for a nutrient solution that could be dissolved in water and in which plants could be successfully grown. This marked the end of the long search for the source of the nutrients vital to all plants.

With the advancement in research, it has been established that efficiency of applied nutrients is only possible when associated with optimum irrigation, as part of fertigation . 

Let us get on to the ACTION to exceed the prefixed national target on pulse production which includes buffer stock as well as the one for export to the needy and hungry nations. With you all the Best of Times Dr. Suresh K Malhotra.

It affects positively to help in the preparation of organic fertilizer and organic compounds to be used in growing crops.

Thanks Maria, I appreciate your concern about the changes in organic fertilizers used in various crops due to changing fertilizer and water doses. 

Nice introductory history of plant nutrition, described in a lucid way ., Dr Malhotra.   Maria  has added another dimension to whole discussion bringing organic fertilizers as well , as long as organic fertilizers are soluble , there will not be any issue with regard to its efficacy ...?

I am very sorry for my  mismatching answers on the topics which is inadvertent as two topics one on pulse production and the other on water-fertilizer interaction are running simultaneously. 

Its alright Dr Reddy. This may happen sometimes. Your valuable inputs we help me definitely. Thanks for you interaction.  

Dr Shirgure and learned colleagues , is there any report  comparing inorganic fertilizers against organic fertilizers through fertigation across different crops. 

Thanks Abhishek for your pdf attachments. 

Worth reading PDFs Abhishek , you have attached . These PDfs throw some light on the possibility of using even organic fertilizers through foliar application  and  fertigation . However , such exercises lack experimental proofs on a large variety  of crops and soils . In limited experiments , where organic fertilizers are used , some supplemental fertilizers in inorganic forms are also used , which a big handicap in declaring the whole practice as organic ...?

Dear friend, If it is fruit tree than the difference in plant size and fruits size and quality may also be due to different plant material. Thanks

The biggest visible effect  of combined application of nutrient and water together is the way , both the inputs compliment each other to improve use efficiency of both nutrients and water , besides impact on different growth related parameters along with quality and available of of nutrients in soil and better nutrient density in index plant parts...

I think it will be evident in the yield

Yes , very much evident through yield response . But , that  yield response , we are willing to get at minimum investment on water and nutrients both..?

It differs from crop to crop and plant to plant.

@Parameshwar I believe all living organisms need balanced/complete nutrients then only they are healthy. We studied about micro-nutrients and macro-nutrients. Apart from this water is the ultimate vital component. Without water highly impossible to exist any organism (few exceptions Xerophytes in case of plants). Obviously more the plants there will be huge competition among them (forget about even or uneven plot) so we have to supply nutrients in the form of manure or fertilizers. Hope the following links give some useful information.

Effects of Irrigation Frequency and Nitrogen Fertilizer Rate on Water Stress, Nitrogen Uptake, and Plant Growth of Container-grown Rhododendron

http://hortsci.ashspublications.org/content/46/12/1598.full.pdf+html

The Appropriate Use of Fertilizer

http://www.agnet.org/library.php?func=view&id=20110804093824

IMPACT OF QUALITY AND RELIABILITY OF IRRIGATION ON FIELD AND FARM LEVEL WATER PRODUCTIVITY OF CROPS

http://publications.iwmi.org/PDF/H041877.pdf

Crop responses to climatic variation

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1569569/pdf/rstb20051752.pdf

Growth and yield of barley (Hordeum vulgare L.) as affected by nitrogen and

phosphorus fertilization and water regimes in Tigray, Ethiopia

http://www.mu.edu.et/mejs/pdfs/V6N1/6-MEJS%2000132-45-57.pdf

Chapter 2 - Physical aspects of crop productivity

http://www.fao.org/docrep/v9926e/v9926e04.htm

Methods and technologies to improve efficiency of water use

http://onlinelibrary.wiley.com/doi/10.1029/2007WR006200/full

Design and Development of Subsoiler-cum-Differential Rate Fertilizer Applicator (attached)

Full Time Horticultural Training Course at The Organic Centre.

http://www.theorganiccentre.ie/courses-and-training/organic-horticulture-full-time-fetac-level-5/

Much bigger question is , how can we rationalise both nutrients and water , without affecting either yield,  quality or soil health related issues..? How does variable rate application in this context , finds its utility ..?

Thanks for asking me this question but I am unable to give any answer due to the lack of my knowledge in this field.

Precision Farming Tools: Variable-Rate Application

https://pubs.ext.vt.edu/442/442-505/442-505_PDF.pdf

'This publication is intended to discuss variable-rate devices that are available, while providing an understanding of which technologies might best fit a cropping system and production management strategy'.

Most important in exploiting the benefits of variable rate application principles is, how effectively , we delineate the production/management zones to implement variable rate application of fertilizers to rationalise the fertilizer-use-efficiency .  While doing so , how shall we interpret the spatial and temporal variability in application response...?

Thanks for sharing. I am working with rice mostly.

Thanks Ramadevi, the PDF is very informative and useful. 

@Anoop yes the question you raised is very useful, indeed it is excellent if we could show all factors together. As per my knowledge research people take particular factor(s) one or two and work on that, may be rare to find out if anybody could work considering all. I come across some interesting articles/links, hope they could provide 'a bit' useful information.

Nutrient/fertilizer use efficiency: measurement, current situation and trends

http://www.fertilizer.org/imis20/images/Library_Downloads/2014_fue_chapter_1.pdf?WebsiteKey=411e9724-4bda-422f-abfc-8152ed74f306&=404%3bhttp%3a%2f%2fwww.fertilizer.org%3a80%2fen%2fimages%2fLibrary_Downloads%2f2014_fue_chapter_1.pdf

Temporal Variability of Crop Response to Fertilizer

http://www.ipni.net/ppiweb/bcrops.nsf/$webindex/312C66162B38CD088525778C00646545/$file/BC-2010-3-Page-16-17.pdf

Application of the ‘‘4R’’ Nutrient Stewardship Concept to Horticultural Crops: Applying

Nutrients at the ‘‘Right Time’’

http://academic.uprm.edu/dsotomayor/agro6505/4R_MattsonVanIersel_Time.pdf

Managing Water and Fertilizer for Sustainable Agricultural Intensification (A reference guide to improve general understanding of the best management practices for the use of water and fertilizers throughout the world to enhance crop production, improve farm profitability and resource efficiency, and reduce environmental impacts related to crop production.)

http://www.iwmi.cgiar.org/Publications/Books/PDF/managing_water_and_fertilizer_for_sustainable_agricultural_intensification.pdf

Rethinking the principles and practices of nutrient monitoring and field testing

in horticultural crops.

http://ipnc.ucdavis.edu/powerpoints/R307_0828_0915_Brown.pdf

Management Zones For Variable Rate Application

http://www.nutrientstewardship.org/implementation/article/management-zones-variable-rate-application

Site-Specific Nutrient Management

http://www.cropnutrition.com/efu-site-specific-nutrient-management

Fluid Fertilizer - Research Projects

http://www.fluidfertilizer.com/fertilizer_research_projects.html

INTEGRATED SOIL MANAGEMENT FOR SUSTAINABLE AGRICULTURE AND FOOD SECURITY IN SOUTHERN AND EAST AFRICA

ftp://ftp.fao.org/agl/agll/docs/misc23.pdf

Information and communication technologies for agricultural development in Latin America

Trends, barriers and policies

http://repositorio.cepal.org/bitstream/handle/11362/35400/S2013050_en.pdf;jsessionid=805C8339C8276D04E3668C1434846480?sequence=1

PROCEEDINGS OF KERALA ENVIRONMENT CONGRESS 2012 (interesting papers and presentations)

http://www.indiawaterportal.org/sites/indiawaterportal.org/files/proceedings_of_the_kerala_environment_congress_centre_for_environment_and_development_2012.pdf

Ramadevi, very much thanks for your excellent feedback and that too prompt .

Yes , you are right Jetty ,  effective delineation of management zones , application variable rate fertilizer application and tailoring the input application through site specific nutrient management , all three go hand-in-hand. some very useful links , you have provided...

Yes, I agree with you Dr Srivastava. Let us debate on some nutrient sensors especially the plant nutrient sensors. 

Thanks Abhishek, proximal sensing of nutrients is a upcoming field for identifying nutrient constraints without disturbing the plant.

This is a very good point Abhishek , and later ratified by Dr Shirgure ..

Proximal sensing of nutrients is one of the effective ways of identifying the nutrient constraints  without coming in contact with the object at which sensing is to be exercised.  Hyperspectral analysis is another field coming up...but , the majo r limitation is , it is confined with certain nutrients like nitrogen predominantly...

Let us discuss the nutrient sensors that can be directly used in diagnosing the nutrient constraints in annual as well as perennial crops .

Dr Shirgure , there are sensors , for some nutrients, but  for nitrogen in most of the cases., it is most effective. for other nutrients , yet a long way to go...

Let us discuss the tailoring of irrigation requirement and  fertilization for a precision farming , how shall these two components be hooked together  to derive the maximum benefits..?

Irrigation and fertilization have to complement each other. Only thing we need to tailor them for maximum crop output.