Leaf analysis, out of many options of diagnosis of nutrient constraints , is considered , by far the most effective diagnostic tool in perennial fruits. An optimum leaf nutrient value with respect to all essential nutrients in relation to fruit yield and quality is the ultimate aim of balanced fertilization , besides safeguarding the soil against any possible nutrient mining . Different irrigation systems are practiced across different belts , which will give out distinct variation in nutrient-use-efficiency . For example, 2.4% leaf N is suggested as optimum value under basin irrigation with flat bed and basal fertilization method , will the same leaf N value be effective under raised bed system with fertigation or hydroponics?
If you accept the definition that all elements are in adequate supply, no adjustment is necessary. (The classic values from surveys are probably a little on the high side because nutrients were not supplied continuously.)
Thanks Paul. What I am interested to know , if there is a citrus orchard under basin method of irrigation ( Nutrients applied exogenously with flood irrigation , I suggest under this practice , optimum leaf N is 2.4 %) . Let us consider another condition of citrus orchard where fertigation is implemented . Here fertilizer use efficiency will be much higher compared to earlier case, do you feel, in this situation also , same optimum leaf N of 2.4% will be required , or lesser than that .
My experience is that 'sufficiency' levels are largely genetically determined. That is why 'critical' concentrations are, by and large, transferable between widely differing environments.
I agree with Paul. If you improve the growing conditions by making used of raised beds, you may, however, increase the plant's efficiency to make use of applied and soil borne nutrients, because of more and healthier roots.
Then , in this situation , whether nutrient optima will undergo any change , should it be on the lower side?
To amplify on what I wrote earlier, and I think that Anoop was suggesting, if anything there may be a small decrease in minimum required foliar nutrient concentrations
I do not agree. As said earlier, nutrient optima is more a function of the plant species/cultivar than the growing conditions.
I agree with both Paul and Piete, but partially. Nutrient optima is said to be physiological constant since it is interpreted on the basis of index plant parts with suitable time of sampling. And index plant part is arrived through following the changes in nutrient concentration and delineating a condition where there is a minimum change in nutrient concentration . This period is defined as index period . Off course , this will very as per plant species and agro-pedological conditions.
My concern is whether changes in nutrient-use-efficiency will affect this nutrient optima. For example, basin irrigation where fertilizers are not given along with irrigation versus fertigation where nutrient and water both are simultaneously pumped into the rhizosphere zone of plant . How do you see the difference in nutrient-use-efficiency under two contrasting condidions vis-a-vis nutrient optima.
You cannot pump the nutrients into the plant, you just make it available. The uptake of most nutrients is not through mass flow, however, if the nutrients are more available and conditions are more favourable for uptake you will need to apply less nutrients, but that does not mean that there will be a change in the optimum levels in the plant.
As said above Pieter, I think this is the key: "if the nutrients are more available and conditions are more favourable for uptake you will need to apply less nutrients" However, I know in crops as Loquat tree, the nutrient concentrations in the trees under drip irrigation were slightly higher than those found in trees irrigated by flooding, but without significant differences.
That's the answer , I was looking for . It is my firm opinion that probably , you need to adjust the nutrient optima ( Using index plant part ....) according to fertilizer-use-efficiency . And , hence , different correct factor could the option to already existing nutrient standards in order to make those standards applicable to varying growing conditions .
Now, We need to get different leaf samples from different varieties at the same sampling period and in different growing conditions. Nutrient concentrations must be analyzed and We must carefully reviewed nutrients standard with this results.
Ana, can you please throw some light , whether there is any need to develop some kind of correction factor for those orchards practising fertigation versus orchards under exclusive basin irrigation .
Yes, Dr Srivastava. Leaf nutrient optima can be calibrated using conventional fertilizer applications versus fertigation. We need to develop a correction factor to adjust such relationship.
Your question is very useful but very little is available to react as a response. But surely we need to develop some simulation equation following basin irrigation as against drip irrigation.
Dear Anoop,
I believe that there is a statistical method to compare efficiencies and select an optimum combination nutrient/irrigation. This is the Analysis of Variance design. I adjunt an article which explains this objective statistical technique with two factors (nutrient and irrigation) in different levels.
I agree , we need to resolve this issue through a comprehensive statistical design , using fertigation treatments versus conventionally used fertilizer treatments. My straight question is , how to arrive at optimum leaf nutrient composition to be used under fertigation , using the same , earlier worked through conventional soil application of fertilizers ..?
Dear Anoop,
This can be investigated via experimentation with several levels of nutrient composition. Thank you, and have a happy Christmas!
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