Dear J.C. Biswas,

Throughout human history, our relationship with the soil has affected our ability to cultivate crops and influenced the success of civilizations. This relationship between humans, the earth, and food sources affirms soil as the foundation of agriculture. Throughout Earth's history, natural cycling of nutrients has occurred from the soil to plants and animals, and then back to the soil, primarily through decomposition of biomass. This cycling helps to maintain the essential nutrients required for plant growth in the soil. Complex nutrient cycles incorporate a range of physical, chemical, and — most importantly — biological processes to trace the fate of specific plant nutrients (e.g., N, P, C, S) in the environment. For a thorough analysis of these cycles, additional reference materials are available. For the purpose of this article, a simplified version of nutrient cycling in natural and agricultural systems is shown in attached Figure .A complex of interrelated technological, land-improvement, and organizational measures for land utilization and the restoration and improvement of soil fertility. 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. Today, agricultural fields are not immune to the forces of nature (e.g., moving water, blowing wind, extremes of temperature) that caused soil erosion in the past. Implementation of agricultural best management practices (BMPs), and through the practice of conservation agriculture, the rate of soil loss can be reduced to approximately equal the rate of soil formation, although often still greater than that in natural systems.(as per attached table) In addition to soil erosion, intensive land use has resulted in deforestation, water shortages, and rapidly increasing desertification of vast areas of the globe, all of which threaten the sustainability of our agricultural systems.

regards,

Prem Baboo

P Baboo,

Thanks for your comments and the attached article. The question is stoichiometric relationship of C, N, P and K is changing because of anthropogenic acitivities. More importantly N:P ratio is making sustainable crop production difficult. Moreover, other element ratios are also changing. Do you think that the answer is very straight forward?

Dear J. C. Biswas

I think, the soil had enough N, P, K contents which means it happened by our cultivation method from long time ago using uncontrollable agro chemical compound. It depressed nutrients availability in soil and had lowered element concentration to uptake by plant. Some biological agent take important role to ensure uptake rate from soil particle into plant roots had killed by extreme soil chemical characteristic changing (pH, temperature, etc) for long period which caused by overdose of chemical fertilizer, even if the medium can also by non biological agent. It is also cause some elements blocking or has catalyzed by other dominated elements so it lock into soil particles. Crop rotation, bioremediation/fitoremediation, land resting maybe can be alternative ways to regenerate land stability and productivity either it takes a long time.

Thanks.

RI Prabowo,

I am confused with your statement. Better we should study more to understand stoichiometry.

Dr.Biswas,you have raised a good question.But at the same time we can not link several things that too total nutrients in organic matter and their relationships.At macrolevel they appear  very attractive but at microlevel they may not convey any thing at least in arable agricultural land.First point, we cannot link K with C and N.We can link C N P S with ratios.Potassium depends more on soil mineralogy,fertilizer K  and manure  addition and crop residue recycling and is not a constituent of any plant organelle.There is  an established good relationship between C and N. C N P S ratios and relations may more valid in undisturbed ecosystems like a forest.Cultivation and cropping depleted from around 30 to 60 % of soil organic carbon over centuries.Nitrogen might have also been lost with carbon.Now they reached some sort of steady state equilibrium under irrigation and good management.Many Long-term Experiments reveal the same.But is not the case with P and S.P is affected by fertilizer and manure additions and S in addition soil minerals like gypsum and irrigation(from ground water).So the ratios worked out with total organic sources may not really govern the availability of P and S.As mentioned by Dr.Singh, the P is not subjected to much losses and K is also subjected to leaching losses in very coarse textured soils. S losses may also be more in coarse textured soils by leaching.So to manage N,P,S,and K we have to follow different strategies in different agro-ecosystems. Nutrient balance sheets may provide better picture of nutrients behavior in agricultural soils and their use efficiency compared to total nutrient ratios in soil organic matter.Even mineralization studies have become more  problematic with P and S (because of resorption and precipitation reactions).

Dear J.C Biswas,

If your concerned is how to overcome the lowering of C, N and P in your soil that leads to poor productivity of the soil I humbly suggest  using of lime to neutralized your soil.

  Regards.

Dear Biswas, maybe my article can bo of your interest:

- Pelliciardi V. 2012. Nutrient (N, P, and K) recycling in traditional soil fertility practices in Leh district: a case study at small farm level. Ladakh Studies 28: 27-35.

You can dowload at:

http://www.ladakhstudies.org/downloads/files/LS28.pdf

All the best. Vladimiro

Dear Biswas, maybe my article can bo of your interest:

- Pelliciardi V. 2012. Nutrient (N, P, and K) recycling in traditional soil fertility practices in Leh district: a case study at small farm level. Ladakh Studies 28: 27-35.

You can dowload at:

http://www.ladakhstudies.org/downloads/files/LS28.pdf

All the best. Vladimiro

 Dr.Pelliciardi,interesting study especially nutrients balance sheet.

Dr Pelliciardi,

Thanks for the paper. I appreciate Dr Rao and Odeza for their valuable comments. Although K is not concerned with C, but uptake ratio in a plant system impair Mg and Ca uptake through the luxurious K uptake. A soil having pH around 6.0- liming might not help for improving crop yield.

Thanks

Reduction of soil organic matter is the main cause of soil fertility depletion and declining agricultural productivity in most agricultural soils.  According to studies global soil acidity occupies 30% of ice-free land and about 20% of irrigated global land has been seriously affected by salinity. Majority of the agricultural productions depend on synthetic fertilizers, and one of the major problems is over application of fertilizers, especially N fertilizers such as urea.

The benefits of inorganic fertilizers, which have played a significant role in increasing agricultural production and productivity over the last half century, have been widely demonstrated since the green revolution. However, the productivity boost provided by fertilizer technology may be reaching a point of diminishing returns, with chemical fertilizer use becoming increasingly unsustainable, environmentally damaging. the application of fertilizer alone is not a sustainable solution to improve soil fertility and maintain yield increases; rather, excessive inorganic fertilizer, especially N, may cause soil deterioration and other environmental problems due to more rapid organic matter mineralization. Thus, maintaining an appropriate level of SOM and ensuring the efficient biological cycling of nutrients is crucial to the success of soil management and agricultural productivity strategies. This can be achieved by integrated soil fertility and plant nutrient management approaches, i.e. both organic and inorganic nutrient sources.

Dr Agegnehu,

Thanks for the linkage.

Biswas asked very important question of practical nature. Actually no one cared about C: N ration with the introduction of high yielding varieties until crop production starting decreasing significantly again. Addition of crop residues and other organic matter is the only solution of the problem. Getachew referred some good linkages.

This is a reality and pertinent issue of sustaining crop prodcuctivity especially in the developing countries. Nutrients mining (increased crop intensity, high nutrients demanding crops/varieties and imbalanced use of chemical fertilizers), reduced recycling of crop residues and organic matter into soil and more importantly soil erosion lead the nutrients depletions (especially N, K and micronutrients) in soil. Balancing soil organic matter (SOM) in soil is rarely considered in crops production! What I beleive is that an integrated nutrients management approach should be followed. Depletion of the SOM shoul  be balanced  through increased use of organic matters (residues, green manures, cover crops and organic manures) and complementing nutrients with inorganic fertilizers.

The suggested measures by Kalidas may prove useful if carefully practiced.