Just give the time to crop stand in the field for utilizing residual P.

There is no way to measure P utilization by plants in the years after application. We assume an overall utilization of 100% on healthy soils and as far as at least neutral ammonium citrate soluble P forms applied according to crop removal. Read more in our papers!

The problem of Phosphorus would be generally deficiency in the Indian subcontinent and African and excess in North America and Europe. 

Phosphorus overload is mostly a problem related to factory farming of animals and distribution being limited by cost factors to raw manures. This is outrageously wasteful from a scarce resource outlook. North America is the most outrageous case study of unintended waste.

In the Chesapeake Bay in maize soybean agriculture 59% of increased Nitrogen in bay waters is traced  to synthetic ammoniated fertilizer use and 35% from the use of raw manures in the maize soybean system of conventional farming..

Using the biological inputs focusing on legume for Nitrogen and using compost in rotation with cover crops this can be controlled completely. This has been measures over the more than 30 years of Rodale Farming Systems Trial and in addition to equaling county yields the systems builds soils in organic matter and allays losses in drought years. The experiment has taken over 33000 data points from intact soil core lysimeters. 

We should not forget that the global limiting factor is fresh water for our food and agriculture and the levels of soil carbon is intrinscally important for water capture and use. Since all plant nutrition is a function of dissolution in water.

Large body of literature shows that mycorrhizal fungi with absorp up to 80% of Phosphorus needed for plants. When luxury Phosphorus is provide the signal to plants is reduce mycorrhizae compromising their ability to withstand drought and absorp other critical nutrients like Zn. 

By focusing on cover and legumes in rotations  covering with cover crops and amendment with composted manure we get a system that causes our soils to improve progressively year after year and the net result is not only more production under normal adversity but better quality food. 

 Dr.Schnug, I agree with your statement .I am aware that your team has generated excellent work on P and at least some papers I could see  in the past.I shall see more in near future.I think if farmer keeps a record of his soil test reports,he can himself see the build up in soil test values of his farm over years because of continuous P fertilizer application.Also the soil test summaries prepared  by soil testing laboratory in an area or by district level agricultural functionary may show the build up of P in a district.Accordingly, the Agricultural Extension personnel/Soil Testing Lab in-charge can provide some what moderated/reduced recommendations to farmers to reduce the rate of P application and utilize the residual soil P fertility.Dr .Hepperly,glad to discuss with you again on an important topic. I understand that there is substantial build up of P in soils of Europe and North America mainly because of application of huge amounts of manure and also because of fertilizer P application.I  agree with you that preserving water quality is very important .In India and Africa the soil test P values are not very high but recent reports indicate that under intensive agriculture P has built up over time in  parts of some districts of India.So monitoring soil P status is important .Also use of composted manures, cover crops and inclusion of legumes in rotation will definitely help and farmers can save on fertilizer P application.

If soil pH is too low, I would firsty suggest liming that will improve soil pH to a rate that will allow P to become more available for plants. Microbiological products are available to 'help' with P availability for plants, so P reserves in soil will be better exploited.   

Soil P builds up to very high values in intensively cultivated areas in India. Particularly in tea and coffee plantations in north-east and south india. Besides soil conservation measures to avoid soil and water run-off, planting legumes, adding farm yard manure to improve soil biological activity, improving mycorrhizal activity, inoculation with phosphate solubilizing bacteria are some means. The tap roots of legumes is known to bring soil P in lower layers and bring it to the surface and leave it there in more available form. Inter-cropping with species invlving surface feeders and deep feeders is well known.. maize-pigeonpea.        

Interesting discussion on one of the practical agricultural topics.We can know the build up of soil P through soil test.But all P soil test methods may not show similar increase in soil test P.After knowing the soil P status, what strategy we should follow to exploit the residual P?.Can we skip P application for some years/seasons or apply P at reduced rates?aA suggested by colleagues Dr.D.Rao and Dr.Hepperly,we can grow legumes as green manure crops,inter crops or cover crops to utilize the residual P in soil.How much benefit the associated or following crop get from the mobilized P by the legume crop.We have now several P solubilizing microorganisms including fungi ,bacteria and mycorrhizae.I do not know whether mycorrhizae can work in high P accumulated soils.Now breeding efforts are going on with bio-technical tools to breed  crop varieties to efficiently utilize the soil/residual P in soils.I request the colleagues to throw more light on these any other new approaches.

A very complicated topic.  Various contributors have hit the main points.  If the soil is acidic then raising pH is often effective in decreasing the strength of P binding to hydrous oxides (the effect depends partly on the dominant cation) and will increase the rate of microbial activity and consequent SOM turnover.  Organic amendments temporarily depress sorption. 

Dear Dr.Paul,Soil pH adjustments(moderate) and organic amendments may help to mobilize the accumulated soil P and its utilization by crops.You are right.

In arid and semi-arid regions, most of the non-available remains as Ca-compounds which are insoluble and non-available. In the long run, I would suggest use of acidifying fertilizers, manures and some residue burning could help partially utilize the residual P. Otherwise, built-up of P has to be there. Another way is to identify and genetically modify the plant to be efficient utilizers of such P pools.

I think a take home is the dramatic contrast of approaching the arid and semi arid soil issues in contrast to acid soil infertility ones. In different soils the approaches will be different.

I think that we should enhance the soil P bioavailability by the type of crop or stimulation of microorganisme which could assume P solubilizing such as rhizobia or pseudomenace..............But the type of soil is very important as considering, under Alkaline or acide sol?

Mr.Latati ,soil reaction,efficient plant root  system and associated microbes in rhizo-sphere soil all have important role in utilizing residual P in soil.

Yes Mr Subba, and we can suggest also crop association such as legume cereal which can mitigate P availability by complementarity and facilitation. Thus, Symbiosis by N2 fixing is considered as key role to enhance P availability under either calcareous or alkaline P defecient soil

Symbiosis is the name of the game in nature and we need to rescue it in our farming systems if we are become sustainable and regenerate our natural resources we all ultimately need for surviving and thriving through its power. In terms of interactions I believe we need to understand that the mycorhizosphere composes the plant root court the fungal court and the rhizosphere microbial population I would like to include also the earth worms which work as the pistons of soil living machine. 

The soil living machine functions as results of the human management through the way the farming system is envisioned and managed. Physical, geological, chemical and biological resources are all in interplay.  If we have a healthy farming systems for instance it should be replete with worms and biological life and not devoid of them which as so often been the consequence of our own intentional or unintentional management and its implications known and unknown.

The fallacy of our current synthetic chemical input farming system has been its intervention without an appreciation for the long term sustainability and the potential to renew and regenerate the system itself through the biology which are the building components.  All these isolated factors are meant to work symbiotically and synergistically and if the result is not such something needs to change.

The biggest change we can envision is that we need to re-establish the native functioning of the systems through the relationship utilizing our own intention and information and those of supporting experts..

Yes Mr Paul Reed it is very important to better improve management technologies for  sustainability of our agrosystem. However, Adopting sustainable technologies to better exploit soil nutrients resources such as P and N has been an interesting research challenge to be resolved. Thus, management of agricultural practices including the intercropping cereals with legumes is so far considered as one of the main agriculture sustainable components.

Dr.Latati,Dr.Hepperly,Integrated farming system may may address several issues raised by you, regarding organic matter,manure use,inter cropping ,residual nutrients use .We need more work with  integrated farming approach.

Integrated farming approach is the best option for many problems. But resource poor farmers and fragmented land holding is the obstacle in adoption of it.

The think one of the management policy in utilizing accumulated P can be, let the crops consume residual P until the Soil test P (STP)  levels declined below or nearby critical levels of P for a certain cropping sequence. When STP level  approaches Critical Limits, follow to apply P fertilizer rates equivalent to the crop removal 

Dr Jagdeep Singh may only partially correct because in his approach crop yields may suffer owing to slow release / conversion of non-available P in to labile P. But crops with low P requirement could be used.

 P application rate's should be decreased it will increase the uptake of residual P by crops.  As Cumulative inputs of P fertilizer and manure for the period 1965–2007 in Europe (1,115 kg⋅ha−1 of cropland) grossly exceeded the cumulative P uptake by crops (360 kg⋅ha−1). Since the 1980s in much of Europe, P application rates have been reduced, and uptake continues to increase due to the supply of plant-available P from residual soil P pool.

Dr.Singh, now integrated farming modules are available even for small farmers.You may please refer to work of ICAR all coordinated research project on Farming Systems Research,Modipuram .I agree with Dr.Ghafoor that when we are utilizing the residual P in soil we may not completely skip the application P fertilizer.Depending on the residual P in soil,as revealed in soil test ,we can reduce the recommended P dose by 25%or 50% and utilize both fresh P and residual P in crop production.Crop yield should be monitored over time to make any midterm correction.Only in soils adequate in available P(above critical limit),   the replacement of  of crop removal( through fertilizer application )is advocated.

Dear Colleagues

I am enclosing a popular article I did on earth worms.

Earth worms could help some of addresses issues in the sub Continent.

I believe the use of earth worm castings are the most effective starter nutrient package. They have a rich amount of Phosphorus and Nitrogen but having the Nitrogen in nitrate makes them much less prone to salt issues. I believe I could teach people at a village level how to use their manure of rearing earth worms with great advantages to your agriculture. I believe it would resolve a lot of issues in your cropping systems.

Dr.Hepperly I will go through your article on earth worms.Our Indian Government realized the importance of vermicomposting and our state governments are promoting the same and some   others are providing subsidy also.As a component of organic farming  vermicomposting is being promoted.Of course expert advice will always benefit.

Some of the suggestions made by researchers are workable to utilize residual P.

I agree with you Dr.Hussain that several methods and approaches workable to utilize residual P in soil are available.We expect good research work to breed varieties for efficient use of soil accumulated P .I also expect more use of mycorrhizae culture to mobilise and access soil P and  more use of bio-fertilizers for P solubilization in rhizosphere.Soil test methodology also needs improvement for better  assessment of  the quantum of residual P in soil (with better soil test)and also the limit up to which one can exploit the soil test P without exhausting the soil .

Phosphorus supply to the crop is affected by soil P, P fertilizer management and by soil and environmental conditions influencing availability of P to plants  and root growth. As phosphorus is an immobile nutrient in the soil, P sorption/fixation is a major problem both in acidic and alkaline soils, where its availability to plants significantly decreases. Even in the presence of reasonable residual amount of P, its availability is limited by  fixation. As you know, the pH range for phosphate availability is 5.5-7, with optimum being 6.5-7. Thus, desorption of residual or applied P can be enhanced by optimizing pH of soils both in acidic and alkaline soils.

The use of phosphate solubilizing bacteria as inoculants simultaneously increases P uptake by the plant and crop yield. Strains from the genera Pseudomonas, Bacillus and Rhizobium are among the most powerful phosphate solubilizers. The principal mechanism for mineral phosphate solubilization is the production of organic acids, and acid phosphatases play a key role in the mineralization of organic P in soil. Phosphorus uptake in many crops can also be improved by associations with arbuscular mycorrhizal fungi.

Application of organic  amendments may also directly or indirectly improve the availability of soil bio-physical and chemical properties, including soil OC,  pH, CEC, soil water content which is essential for nutrient availability and soil microbial biomass.

Workable suggestions from Getachew, thank you.

I also compliment Dr.Getachew for summarizing good points for the benefit of followers and viewers