As we know annual and one season cultivating crops need minimum amount of nutrients for growth during initial period. But most of the cereals, pulses and flowers recommended 50% N, 100% P & K. Use efficiency of the macro nutrients vary crop to crop and was estimated N-30-35%, P-10-20 & K-70-80%. If we change the pattern of fertilizer recommendation based on growth stage of crop, few possibilities will open to improve nutrient use efficiency with sustainability.
Full amount of N at basal leads to losses of N in the form of leaching, denitrification etc. as N is highly mobile in soil. Thats why only half amount of N is recommended as basal dose. Whereas P is immobile and K is less mobile in soil and no need to split doses of these nutrient. Sometimes in light soil, splitting of K fertilizer is advocated.
Dear sir, my preview of raising the question is to understand the nutrient dynamics on vegetative growth and if we recommend 10/15/25/30 % within 25-30 DAS, will increase nutrient use efficiency or not. It is researchable
This is a very good question , but its answer will not be so flat. Such questions should be more reliably answered through experimentation on partitioning of the NPK across different time period within vegetative phase also. And , this needs to be worked out for different crops and major soil types. Our colleague, Dr Shahrajabian has rightly put out in his response , it needs to be looked into soil test-based recommendation . Unfortunately , we lack conspicuously on the issue of interpreting soil test results while dealing nutrient requirement of a specific crop...or different crops on the same soil type, atleast at either great group or sub-group level...
It is correct that we are advocating to split the N fertilizer to reduce loss and increase use efficiency as N is very mobile nutrient . Similarly we advise to place the P fertilizer as they are immobile and unless and until root present there it may not be available. Again we find that a bulk amount of nutrient is needed during the critical growth period of the crop, which comes between 6 and 8 weeks of crop age and that time we need to supply the nutrient to the plants, especially essential nutrients, if they are not available in sufficient quantities in the soil. Actually there the split concept of application has come . But for the plant nutrient supply the basic concept should be:
1. Nutrients removed must be return to the soil.
2. Organic carbon level should be maintained and enhanced.
3. Soil physical conditions should be maintained and upgraded.
4. Build-up of abiotic stresses should be minimal.
5. Soil quality with respect to soil acidity/toxic elements must be sustained.
6. Degradation of land due to soil erosion must be controlled.
7. Nutrient use efficiency should be maximum.
Dear Dr.Manikandan,the basic point is, one has to supply the plant nutrients as per the demands of the crop at different growth stages.Do you think that most of the uptake is finished or completed within 25-30 days, especially in cereals? Nutrient like N ,which is subjected to different kinds of losses in soil- plant system, has to be applied in splits as per uptake requirement at different growth stages.The current thinking that one can reduce the basal dose and apply relatively more amount at stages like tillering,grand growth and panicle initiation stages(names of stages may change with crop) where the demand for N is more.Nutrient demand at reproductive stage is also important for nutrients like P. I agree with the comments of Dr.Choudhary for nutrients P and K.However in case of P if sufficient P is not taken up during vegetative stage (for translocation to grain) and if soil supply is inadequate in reproductive stage(for direct uptake in reproductive stage) the crop may face the limitation of P.So one can think of foliar application or another split application of P at flowering or panicle initiation stage.Split application of K is also advocated in rice in some states especially on sandy or coarse textured soils.
Conversions of nitrates is a very fast procedure to avoid this and leaching of the N fertilizer it is applied in 1/2 dose while P and K used as full in basal dose.
Nitrogen, the only essential plant nutrient which is volatile and highly mobile in plant and soil system. Due to mobile nature of this element, it undergoes several losses like leaching denitrification, volatilization and some time fixation in case of ammonium ion..In order to increase use efficiency of nitrogen or reducing its losses, we have to make split application so that nitrogen may also be available for uptake during peak demand period ( in between different stages of the crop) and rest of the crop growth cycle..because very small amount of nitrogen applied as basal application may be taken up by the crop due to initial period of crop growth...
There are certain premises of fertilizer application based on crop , soil test value, and importantly the principles of 4R stewardship .These issues need to be addressed in order to ensure that applied fertilizers are used maximum without facilitating their leaching into groundwater...
Ms.Verma,you have already answered why we need to apply N in 2 or more splits- both to avoid losses and keeping in view the requirement of N in later stages of crop growth,say tillering, grand growth, panicle initiation etc.Compared to N , such nutrient losses are minimum in case of P and K and so they are applied as full dose at the time of sowing.Under certain conditions K is also split especially in case of rice crop when grown under waterlogged conditions, in light or coarse textured textured soils, late sown conditions or mid- season drought condition etc.Even though scientists are not recommending,some rice farmers are applying P in two split doses as complex fertilizers along with N and K.We have to consider both losses ( leaching and volatilization losses of N,fixation of P and K) of a particular nutreints in different soil- crop-climate condtions and requirement of nutrients at different crop growth stages in deciding application nutrients.Our ultimate aim is to increase the nutrient use efficiency in soil-plant system.
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