Dear Vinod, your question is good but should have been posted in a more direct way . Black soils of smectite nature are considered more fertile than any other soils , simply because of the finer texture. Nutrient- as well as water- use- efficiency are much higher.  Tur dal means Pigeon pea crops has preferential  requirement of sulphur followed by  Mg  , B, Mo , in addition to N to trigger off the  process of symbiosis. I propose another question to my colleagues, such question gives  rise a concept , CAN A SOIL BE TAILORED TO MEET NUTRIENT DEMAND OF DIFFERENT CROPS. This is where our art of soil fertility management lies to raise a variety of crops through different management options .

Hello Vinod,

Please give more detail about the soils.  Are they grey cracking clays of neutral to alkaline pH that are described as Vertisols?

Do you want to know the micronutrient content of such soils or its bioavailability?

Regards,  Paul.

Dear Vinod, your question is good but should have been posted in a more direct way . Black soils of smectite nature are considered more fertile than any other soils , simply because of the finer texture. Nutrient- as well as water- use- efficiency are much higher.  Tur dal means Pigeon pea crops has preferential  requirement of sulphur followed by  Mg  , B, Mo , in addition to N to trigger off the  process of symbiosis. I propose another question to my colleagues, such question gives  rise a concept , CAN A SOIL BE TAILORED TO MEET NUTRIENT DEMAND OF DIFFERENT CROPS. This is where our art of soil fertility management lies to raise a variety of crops through different management options .

Yes Paul , he means with cracking  basalt- derived smectite rich soils.

Black soils are rich in micronutrients like calcium, magnesium and iron.

Dear Vinod,

The availability of micronutrients are very much a function of soil pH. 

When soils are alkaline iron will be deficient in many crops this is a function of solubility and the presence in the soil.  Most micronutrients are more available in the acid rather than the alkaline environment.

In terms of relative amounts in soil Iron and Manganese are usually more present in soil than Zinc, Copper, Boron Molybdenum and cobalt in that order. For a legume like pigeon pea the micronutrients can be effective in stimulating the biological Nitrogen fixation through rhizobium bacteria. Zinc Cobalt and Molybdenum is formulated to simulate biological nitrogen fixation in  legumes and might be useful for pigeon pea.

Organic manures and composts can be good sources of micronutrients and have value in correcting micronutrient deficiencies.

Diagnosis is important. Micronutrient dificiencies can be pin pointed using plant tissue analysis and soil analysis to develop a plan of attacking deficiency issues.

Paul I agree with you , its not only black soils , but in most of the soils , we need to address the multiple nutrient deficiencies . That is only possible , when we have a robust system of nutrient diagnostics , very specific to soil mineralogy and crop as well. If our nutrient constraint diagnosis is not precision -based , probably , we will not be able to harvest the expected dividends out of balanced fertilization . Find below my research papers in PDF version  dealing with nutrient diagnostics on  smectite dominated black soils

Yes, DR. Annop and Dr. Paul, I agree with you. Soil pH is very important criterion to decide availability of micro nutrients and P. Therefore, the pH will decide the availability not only its color, though black color of soil is an indication of more organic matter, if not contaminated from industry residues.

Dr Nazir , in these smectite rich soils derived from basalt , even calcium carbonate nodules  of  recent origin,  serve as a potential source of nutrients like Fe, Mn, Zn , a further supplement to what Dr Hepperly is saying .  Find below an interesting PDF  from our research desk .

Yes, I agree with you Dr. Anoop Ca availability will be very high if CaCO3 is present but then the soil may be alkaline and availability of micro nutrient will decrease. Even CaCO3 nodules can adsorb some of the nutrients, especially Zn. 

Zinc is often reported to be deficient in black soils beacuse of alkaline pH and calcareousness. In respect of pigeon pea avaialability of Mo may be crucial for nodule formation. Having said that, I must say that the best pigeon pea is grown in black soils (medium and deep) in north Karnataka under rainfed conditions. 

Dea Ghulappa S. Dasog Mo as you know is critical for Rhizobium bacteria that form nodules it plays a role as a enzymatic co factor in the biological nitrogen fixation process. While most alkaline soils can engender micronutrient deficiencies especiallly over 7.3 pH in the case of Mo is availability is higher in neutral and slightly alkaline condition making distinctive among the micronutrients. Pigeon pea is known to to be effective in producing psidic acid an organic acid which can be very effective in scavengering scarce Phosphorus under acid conditions it also has abiltity to be very effective in biological fixation of Nitrogen and its deep rooted system is wonderful for breaking compacted soil layers. India in their domestication of pigeon pea offers the world a great treasure which I dare to say is under appreciated all over. I my love to earth them with rice.  Greater use of pigeon is very important to improve crop agriculture sustainabilityl. 

Thank you for the excellen input Dear Dr Hepperly.

The key question is: what do you mean with the term "black soil"?. Only the color?. are afected by Na?. That is an important question and the answer depends on this point.. Despite of this, I have read some interesting answers in both directions.

Jose , black soil means smectite rich soils , derived predominantly from basalt parent material    . And accordingly the question was responded

The black soils in Indian context means Vertiosls and Vertic Inceptisols, largely. Na affliction is always in pockets and not the general black soil areas.

The black colour of black soil is due to presence of titaniferous magnatite compound not due to organic matter. Black soils are poor in organic matter content.

In North America and Europe in the grassland plains the use of potassium hydroxide gives an extraction of humic acids which are decidedly black in color and associated with high fertility and utility. Excellent observation by Doctor Singh this is certainly not the case in the low soil organic black vertisol of the tropical Indian subcontinent. In this condition the high salinity and the high pH will immobilize critical micronutrients in that case in a crop like soybean you will find Iron chlorosis or zinc deficiency. This may not be because of absence of iron or zinc but of the biogeochemical reaction makes the micro element insoluble. As Singh has pointed out side by side we have black and red soils on the same subcontinent. I suspect and correct me that red soils would be leached more thoroughly on humid areas and ones would be found in more semiarid region although might come from the same parent material the difference in climate would produce a different soil result. The black Indian soil would have issues related to its physical tightness but be quite fertile under the right conditions. The more leached red soil would probably result in better physical mechanical quality but less nutrient fertility potential.

 All nutrition in the crop plants depends on the mineral being put into solution and then absorped and utilized by the plant. That is why pH of the soil should be a primary consideration.  Organic matter in soil can increase the amounts and solubility in some cases but not all cases. We need to get our local issues all ironed out to improve the productivity and quality of our crops. If we map out the areas high in alkalinity and salts we can use elemental sulfur and calcium sulfate as part of a remediative process.

For the micronutrients we need to use a complete soil analysis combined with plant analysis to conclusively identify the problems and issue. We then develop a remediative strategy, apply the soiution, and monitor how the plant and soil reacts. After the balancing effective maintenance and monitoring becomes less critical but still needed.

Hope you find some food for thought in this discussion.

Dr.Singh how can you say black soils are poor in organic  matter? In comparison to which predominant Indian or other country soils you are commenting on?

In terms to central North America blacker soils are generally higher in soil organic matter. Pedro Sanchez a world tropical soil expert says this observation does not fit many tropical soils.

The best way to settle this is to get the data and determine what it actually mean. Usually the more data the better interpretation and planning.

The ability to accumulate soil organic matter from data in India and North America increases with higher Calcium and Clay content. While soil organic matter and clay has overall negative total charge and will tend to repel each other the use of Calcium with its two cationic charge binds the clay and organic matter into a complex which has better persistency give a fluffy texture to a material that otherwise is more dense. The binding and flocculation gives a greater specific density and associates with more sites for microbial inhabitants.

It would be interesting to contrast the soils in Icrisat which are in close approximation and are red and black for their contrasting or similiarity in soil organic matter.

Thank you for your valuable feedback's ,these discussions helped me a lot.

Thank you all once again.

Does anyone have the soil analysis of the black and red soils at Icrisat? If you could share it would interesting because they are under the same environment but apparently come from distinctive mineral sources.

When one works with Cajanus cajan, the pigeon pea, I agree with Doctor Srivastava that the nutrition need should be tailored first to the crop, then second to the soil and then thirdly to the variety.

With a grain legume like pigeon pea the requirement of Nitrogen can be completely satisfied by the biological Nitrogen fixation. The Rhizobia bacteria need to be available by inoculation or soil population.

Molybdenum, Zinc, Cobalt, and Boron are very important for the satisfying of Rhizobia bacteria nutrition requirement. In turn when the plant is well nodulated it favors the mycorrhizal fungi.

Consider using Rhizobia inoculation and seed treatment with micro's big potential benefit from a small application. A few grams of Rhizobia and micro preparation gives assurance of over 100 kg per ha of Nitrogen contribution for the pigeon pea which extends to the following sorghum crop in rotation for example.

Nitrogen application has the largest fossil fuel imprint and environment impact of all farming practices.

If the cropping systems does not reduce the problems with erosion the sustainability of fertility programs will be greatly compromised. I am asking you to consciously consider the implementing of farming systems rather than a single crop consciousness.

This will reduce erosion to less than Universal Soil Loss Values when applied optimally.

For the conversion of depletive farming system in North America to a regenerative one the legumes need to be the provider for Nitrogen requirement and plant coverage needs to drastically increased to reduce soil erosion.

At the Rodale Institute Farming System the use of Wheat hairy vetch Maize rye soybean rotation provides a grain crop yearly but covers the ground between crops eliminating the erosion. When combined with mixed farming composted manures add to regenerative effect since compost is gives a prolong soil advantage.

The Rodale farming has converted over 150 hectares to soil organic levels of over 5% from less than 3% originally. With this type of farming the erosion issues are not only succumbed but the soil regeneration resolves global greenhouse gas contribution through increase of soil carbon and nitrogen content. The increases in soil organic matter result in increases in the other major and minor elements at the same time.

Dr.Hepperly,Very good account on pigeon pea nutrient management for higher productivity ,fertility improvement and overall productivity improvement of Vertisols.

Dr.Hepperly,You may download the following publication from the publications of Suhas P.Wani of ICRISAT in Researchgate. .Characterization of benchmark spots of selected red and black soils in semiarid tropics of India for identifying systems of carbon sequestration and increased productivity in semiarid tropical environments Report no.42 ICRISAT,Patancheru. The report contains description of ICRISAT farm and other soils from SAT zone

The major micro-nutrients in black soils are Zinc, Molybdenum, Iron, Cupper, Mangnanese, Boron, Chloride.

Friends , let me float another hypothetical question , how do you feel , a  soil could face a number  of fertility constraints,  depending upon the crop requirement , and the target yield. A given soil , irrespective of crop , may not face any nutrient constraint if target yield    is well within the  nutrient removal far lower than the application or reserve pool of nutrients in the soil .  If we fix the target yield on the higher side , the removal will immediately exceed the  application of  inputs , the crop will face the nutrient constraint  of varying magnitude .  Do you feel ,a soil is optimum or suboptimum in a given nutrient depending upon the yield target?. Your responses please.