its not only the question which fertilizer, its more the question which production philosophy: organic farming is proven to be the most sustainable way to manage and optimize nutrient fluxes in those areas.

 I think integrated nutrient supply involving the use of reasonable/affordable amount of fertilizers,manures/composts (from livestock enterprises and locally- available organic resources) and biofertlizers/ bio-cultures may a better option to maintain/sustain reasonably good yields,maintain soil health and meet the food and nutritional security of people.

Indeed. Thank you Professor Eward

Thank you Dr Annangi. Integrated use (both optimum and type) would be a very good option

The answer is not a straight forward YES or NO. It depends, first of all, on what is meant by "intensive fertiliser use".  It also depends on the nature of soil and the kind of crop that is being cultivated. Generally, integrated fertility management is essential, as described by Amandi Rao above. Fertilisers are good and necessary for African soils, but require to be used properly, with environmental concerns considered and integrated soil fertility management principles upheld. Organic - Inorganic interaction is a key part of this, but not possible in all cases.

Sole application of chemical fertilizer is not a good practice as the soil's capacity to hold nutrient is low and susceptible to leaching loss. Regular application of different organic sources with chemical fertilizer may be helpful to increase the nutrient holding as well as water holding capacity of the soil. In addition, split application of fertilizer in such soil may increase the efficiency of fertilizer applied.

No I didn't agre there are various other factors which causes this. Availability of moisture rainfall occurance, intensity, temperature solar radiation the most important factor

Thank you all for your constructive answers and comments. Application of chemical fertilizers enhances production but simultaneously emphasis also should be given to long term impact on soil quality. The present sole chemical fertilizer based intensive production in many Sub-Saharan countries is believed to be physically deteriorating and biologically deactivating the soil. There is misconception among crop production experts, researchers and particularly political leaders on issue of fertilizer consumption, crop productivity, yield, long term effect on soil acidification, organic matter depletion, green house gas emission, Eutrophication etc. What recommendations (may be policy or other) can we forward considering the dominant type and characteristics of soils, climate dynamics particularly moisture and temperature, cultivation since antiquity...etc?

sorry for earlier reply, i  think integrated nutrient management approach will be the best option, apart from that conservation agriculture will help alot and  is the appropriate option for soils of Sub-Saharan Africa

Intensive chemical fertilizer use is not the way forward ecologically and economically. Keep in mind, small scale farmers who produce the bulk of the food in this region are poor and have little or no access to chemical fertilizers which are expensive coupled with the inherent problems posed by soils in this region and high nutrient losses. With this in hindsight, an integrated nutrient management approach {organic-inorganic-biofertilizer} appears to be the best. The INM approach is sustainable economically and ecologically, however this might not work in some regions with respect to crop management systems and availability of organic materials. The onus lies on soil scientist, agronomist and policy maker in those areas to formulate sustainable alternatives that fit best.

Dear Alem Hagos Hailu,

Indeed, your soil description is right; most African soils are amongst the worst soils worldwide. It is therefore that huge parts of Africa are already overpopulated; overpopulated at a low population density in absolute sense. It implies that the African population does not have another choice than using external inputs, chemical fertilizers, to increase the carrying capacity of the continent. Most of its soils are so poor that limited numbers of livestock survive on low quality fodder, producing limited amounts of low quality manure. Using such manure and compost does not improve soil fertility; it helps to slow down soil depletion.

The soils being as you describe, the use of chemical fertilizer alone is very risky. Integrated soil fertility management is required, the combined use of chemical fertilizer to nourish the crops and of soil amendments, in the first place for improving the soil organic matter status. In this way, both the capacity to hold water and to keep nutrients in the top soil is improved in this way. Low quality manure and crop byproducts are effective soil amendments.

Please realize that the average use of chemical fertilizer is already 135 kg/ha, while in sub-Saharan Africa (SSA) it is just about 10 kg/ha. The average yield of cereals is worldwide almost 4 t/ha, the yield in SSA is below 1.5 t/ha.  Countries with well-developed agriculture reach yields of 7 t/ha or more. Most of world’s food insecure countries are SSA countries. Below 135 kg/ha of fertilizer use, the average world use, a strong positive correlation exists between fertilizer use and food security. Developing their agriculture using external inputs such as fertilizers and improved seeds can help countries of SSA also to trigger socio-economic development.

For details and more arguments, please see my publications. A list is available under “About me” on my website AgroBioAfrica (www.henkbreman.com).

Henk Breman

The soils in sub saharan Africa are mainly made up of  1.1 clay minerals kaolinite .There is one layer of aluminium and silicon sandiwiched with oxygen and hydroxyl ions ,thus, there is a van der waals forces of attraction between the silicon and aluminium layers with little space to absorb water and nutrients .Besides, the isomorphous substitution between Al and Si leaves one negative charge and when you add chemical fertilisers they can not held by one negative and  are washed away with little utilisation by crops for bumper harvest .also,the soils are pH dependent .The use of organic fertilisers will add more negative charges to soils and will retain more nutrients for crops use which chemical fretilisers can not supply .Hence,there is need for appropriate management techniques ranging from reduced tillage  practces, cover cropping ,planting of  legumes,application of organic fertilisers ,avoiding large scale opening of land to reduce devastating effects of rainfall and organic matter decomposition and soil conservation practices.

In order to make SSA soils more productive, better intervention would be to opt for live stock production and to grow fodder crops which require least quantities of nutrients and drought resistant to sustain water scarcity. The use of chemical fertilizers, in the long run would adversely affect the soil quality and endanger soil sheltered flora and fauna. The contention of Mr. Henk Breman that "Most African soils are amongst the WORST SOILS worldwide" quoting in his own words, to say least is hurting to a Soil Scientist like me. Why to designate them as worst? They are not to be blamed for their status, since it is humans who made them to become worst. Further, by intensive chemical fertilization, we degrade to make them lifeless. Whereas, as a Soil Scientist, I love all soils of the world equally and render them more and more fertile and flourish lively. The tragedy is human over exploitation driven by extreme greed to take out more from soils and give them least. In analogy, humans would be extremely happy and delightful, if cow can yield milk to meet our greedy demands without feeding fodder. Given a chance, I have the confidence to render SSA  soils highly fertile and productive and cause economic stability of those living there. 

Decline in soil fertility is becoming an issue in sub Sahara Africa since land is not given time to regenerate or rest so there is need to return the nutrients back to the soil.

I would suggest organic soil amendments for farmers so they are sustainable for farmers and environment at large.  Farmers identify legumes to fix nitrogen and make own manure from their farm waste. Thank you

Bruce

How to meet fully the nutrient requirements of crops and sustain reasonably higher yields in organic farming is big question?On farm nutrient regeneration through legumes and nutrient (in residues and wastes) recyling assume a lot of importance in organic farming.The following paper uploaded in researchgate by Dr.E.Schnug (one of the followers of the question) provides useful and interesting information on the aspects mentioned above.

Organic plant production-Limited by nutrient supply?An over view. By Paulsen,H.M. et al. In: More Sustainability in Agriculture:New Fertilizers and Fertilization Management-18th International Symposium of CIEC, Proceedings-CIEC 2009 pp.373-380.

Dear colleagues,one more interesting paper  highlights the nutrient balance(budgeting) and dynamics in soil under organic farming.The paper focusses more on N  and P.Unless substantial amount of manure or compost is applied every year,P balance in soil and requirement  by crop may become crucial.How to meet the P needs of crops in organic farming is an important issue.The folllowing paper from researchgate can be consulted for more details.

Nutrient dynamics of organic cropping systems:A tricky balance Walker,R.L. Conference paper August 2010 

https://www.researchgate.net/publication/281284601

Conference Paper NUTRIENT DYNAMICS OF ORGANIC CROPPING SYSTEMS: A TRICKY BALANCE

Dear all. Very good explanations and feedback. The idea of Mr. Henk Breman on soils of Africa is to explain the fertility & productivity status of the soils because of continuous cultivation since antiquity, less return, degradation etc... & he is right, we should take as a positive feedback.

Further recommendations regarding common understanding between soil scientists, agronomists, policy and decision makers to support our community economically without degradation.

Thank you all again

Thanks for all reactions, allowing me to be more clear regarding my statement that both for agricultural as for socio-economic development in sub-Saharan Africa (SSA), chemical fertilizers are a “condition sine qua non”. My apologies, Mr. Kunuthur Srinivasa Reddy, for stating that African soils are amongst the worst world-wide· It is the judgement of an agrobiologist through the eyes of a farmer. It concerns the “natural” agricultural production capacity of these soils, which lies for the dominant soils between less than 500 and 1500 kg/ha of cereal equivalents. The average is presumably less than 1000 kg/ha. Through soil depletion by overexploitation, in reality the yields can still be lower. In practice, yields are somewhat higher (even without chemical fertilizers), thanks to i) applying organic amendments such as manure and compost and ii) laboring soils, causing more aeration and therefore stronger soil organic matter mineralization. The latter process and overgrazing of range- and waste lands are the key mechanisms for human soil depletion.

African soils are not among the worst world-wide through soil depletion. The soils being “naturally” poor and climates difficult, African population density is low in comparison to most other continents. African soils are in the first place poor by the geology of the continent; it is compost out of tectonic plates which are less disturbed than elsewhere. Nutrient losses, for example through leaching, have occurred during millions of years.

Where soils have been disturbed, also in Africa, soils are young and rich, and it is there where population densities are high. In the small country Rwanda, for example, the volcanic regions in the North have a population density of more than 1000 hab./km2, in the East with its sandy soils, the density is less than 100 hab./km2. Soil depletion is much stronger for the fertile volcanic soils than for the poor sandy soils of the East. Therefore, chemical fertilizers are the most effective on the originally fertile volcanic soils!

Based on local organic amendments only, the crop production can only be significantly improved when for each hectare with crops at least 5 – 6 ha of pasture or rangeland well stocked with livestock exist! It is pity that in most of SSA the availability of land is already since long too limited for it. And where it is still possible, for countries with deserts (e.g. in the Sahel and in Southern Africa), the best land for livestock is found far from the land where crop production is possible. It is therefore that chemical fertilizers are indispensable for improving agricultural productivity and for rural development. Until now, most production in SSA is still biological production. Promoting biological agriculture as THE production, is helping to keep SSA poor and hungry.

Dr.Breman,thank you for the background information on agricultural situation in Africa.As I understand the organic sources are limited in availability and the inorganic fertilizers are costly.So a better option is complimentary use of organic and inorganic sources of nutrients to get sustainable yield and also safeguard soil health.The following brief  but pertinent review discusses important aspects of the use of organic,inorganic and both sources of nutrients.One can find several important papers ' citations from India in the review.

Mixing manure with chemical fertilizers,why? and what is after?El Sheikha AF (2016) Nutr Food Technol 2(1):doi http://dx.doi.org/10.16966/2470-6086.112 open access publication

Thank you very much Dr. Breman for the holistic picture provided on SSA soils. Oft repeated slogan in news media is the term 'Global Village' to mean that world has shrunk to a state of a village with respect to reach any part of the world in least time by air travel. Whereas, in true spirit, natural resource poor areas of the world such as SSA should be helped by other countries of the world with a sincere political will and determination instead of shedding a crocodile tears and echoing universal wellness for global publicity minus practice. The SSA soils can not remain as orphans as they are precious part of the world ecosystem. It is essential to provide the necessary inputs to make SSA soils to make them productive causing all interventions.

Hi! Greetings!

Many thanks to Dr Breman who had worked so much on Sahelian pastures. We are acknowledging this scientist for several models he had built for predicting productivities of Sudanian and sahelian pastures. The present question is raising the challenge of food security and determinant factors in SSA. As Breman has stated, It is true that based on local organic amendments only, the crop production can only be significantly improved when for each hectare with crops at least 5 – 6 ha of pasture or rangeland well stocked with livestock exist! It is pity that in most of SSA the availability of land is already since long too limited for it. And where it is still possible, for countries with deserts (e.g. in the Sahel and in Southern Africa), the best land for livestock is found far from the land where crop production is possible.

In this context, avoiding the use of chemical fertilizers might require the development of compost or organic fertilizers industries! Is this possible in the SSA?

Nowadays, African States are experiencing Ecological Organic Agriculture Initiative (EOA-I) which belongs to the Commission of the African Union. The EOA initiative results from the usual practices in conventional agriculture, the harmful effects of climate change on agriculture. The challenge for achieving food security is to find other alternatives to deal with this problem. One of the alternatives adopted by the African heads of State to meet the challenge of food security is the ecological and biological agriculture which takes into account the realities of local communities, biodiversity and local conditions. The project Mainstreaming Ecological Organic Agriculture (EOA) into National Policies, Strategies and Programmes in Africa is being implemented since 2014 for duration of 5 years. Hope this initiative generate results that could be conclusive to the present question we are discussing.

Hi,

By reviewing some literature for other purposes I found this paper: Is increasing inorganic fertilizer use for maize production in SSA a profitable proposition? evidence from Nigeria. Lenis Saweda O. Liverpool-Tasiea, , , Bolarin T. Omononab, Awa Sanoua, Wale O. gunleye

http://www.sciencedirect.com/science/article/pii/S0306919216303785

Which may help answering your question.

Best,

Léa

Many thanks to Lea!

Regards

Do you think Intensive Chemical Fertilizer Use is the appropriate option for soils of Sub-Saharan Africa? I do not agree with that strategy. In relation to this question when synthetic chemical fertizers are an option for the soils? I would be concerned that like you state many soils of Sub Saharan Africa are acid and not nutrient values and the common used ammoniated fertilizers in these conditions would not necessarily resolve any of the issues but can instead contribute to increased soil acidity. In addition the application of ammoniated fertilizers can stimulate the loss of soil organic matter which is already much depleted in many African cultivated soils. This is so important because the biggest food limitation is related to periodic drought and water capture and recycling depends on soil organic matter. Many African soils at less than 2% soil organic matter have greatly reduced ability to percolate, retaind and recycle water needed for the effective farming system.  I believe for Africa the concentration needs to be on improving soils by reducing soil acidity constraint and improving the soil organic matter content. In terms of  fertilizer the use of starter fertilizer would be most implementable focusing on Phosphorus. This shoud  an adjunct practice to improving the soil pH and soil organic matter by improved farming systems focusing on crop rotation, organic amendment and legume production. If we improve soils the soils tend the plants and the farmer will need to be less dependent on expensive imported synthetic inputs with their negative environmental energy and greenhouse gas food prints. While North America and Europe have been successful in elevating production based on synthetic chemical inputs this has also led to issues in the health of our water systems around the World. 

FYI: Soils of Sub-Saharan Africa are known by their low nutrient retention capacity and high leaching susceptibility characteristics. In terms of Africa the teaching of liming and composting as well as crop rotation and integrated farming is the best approach with an increased eye to targeting the actual improvement of the over time rather than input focus which is favored by vested interests in the inputs. 

I think there is a need to specify the part of Sub-Saharan Africa (as not all have the same setting regarding the soil structure and texture), also on the type of crop to be grown, and even the farming system orientation: cash crop (like the case of cotton for example, which is mostly grown under specific recommendations for the quantity of fertilizer…but, regardless of these issues,

I totally agree with Paul Reed, on the idea of composting and more precisely the case of soil with low organic matter (like in the West African Savanah) or liming (like the case of tropical Oxisols of Congo basin, in the central Africa), are the kind of long term solution (mostly for peasant farmers) rather than short term investment (which could also be fine for commercial/industrial agriculture such as Rubber or Sugar cane plantation...).

Dear Paul Reed Hepperly,

I do not have problems with your description of the problems of soils in sub-Saharan Africa (SSA). I do not agree with your recommendations, which are much too easy. They may seem reasonable, as long as you do not quantify anything and neglect cost:benefit ratios of your solution: “an adjunct practice to improving the soil pH and soil organic matter by improved farming systems focusing on crop rotation, organic amendment and legume production”.

Indeed, in parts of SSA, soil acidity is a serious problem and, I agree, certain fertilizer will aggravate the problem in time. It is therefore that I studied the soil acidity problem is the heart of Africa (Central Africa’s Great Lakes Region) and developed with colleges a manual for solving agricultural problems related to soil acidity. A key element of this manual concerns the profitability of liming. Some conclusions:

1. Liming without inorganic fertilizer will further deplete and degrade the soil;

2. In view of transport costs, it is at present prices difficult making liming profitable.

3. The profitability improves by combining fertilizer use and liming, thanks to strong yield increases.

Do not consider African farmers as being “the bottlenecks” of African agriculture, your “crop rotation, organic amendments and legume production” are key elements of their production systems. As I indicated in my first reaction, organic amendments are used a lot, but –caused by poor soils and difficult climates- their quality is low and their availability is limited in view of the existing requirement determined by population density. Applying chemical fertilizers will increase strongly both the availability and quality of organic soil amendments.

I studied also the option “improving soils by legumes”, and developed a decision support system concerning their use for West Africa. A good illustration of the knowledge and experience of farmers in SSA: legumes are important components of production systems in the Northern part of West Africa, where soil-N deficiency dominates over P deficiency. In the Southern half, the opposite is true and the contribution of legumes in production systems is much lower. It is often difficult to stimulate legume growth with phosphor fertilizers; the value:cost ratio is unfavorable. Too often it is, for example, financially more interesting to increase meat and milk production through N-fertilized fodder than producing more legumes using P fertilization.

I like to repeat what I suggested in my first intervention: Improve the food security in SSA and accelerate rural development by the use of more chemical fertilizer in an integrated soil fertility management context. Nourish crops with fertilizer in the first place, improve and maintain soil quality by using soil amendments such as compost, manure and lime. I like to add: For making the use of chemical fertilizers, lime and improved seeds more profitable, governments have to help improving the access to input and output markets for farmers, the private sector should be supported in developing these markets better, and farmers should be supported in adopting the technologies related to external inputs. In this way, the use of external inputs will become much more profitable than today, and much more organic matter becomes available for soil improvement.

Dr.Breman,I agree and support the last paragraph of your comments.

 The myth of nitrogen fertilization for soil carbon sequestration.

Khan SA1, Mulvaney RL, Ellsworth TR, Boast CW.

Author information

Abstract

Intensive use of N fertilizers in modern agriculture is motivated by the economic value of high grain yields and is generally perceived to sequester soil organic C by increasing the input of crop residues. This perception is at odds with a century of soil organic C data reported herein for the Morrow Plots, the world's oldest experimental site under continuous corn (Zea mays L.). After 40 to 50 yr of synthetic fertilization that exceeded grain N removal by 60 to 190%, a net decline occurred in soil C despite increasingly massive residue C incorporation, the decline being more extensive for a corn-soybean (Glycine max L. Merr.) or corn-oats (Avena sativa L.)-hay rotation than for continuous corn and of greater intensity for the profile (0-46 cm) than the surface soil. These findings implicate fertilizer N in promoting the decomposition of crop residues and soil organic matter and are consistent with data from numerous cropping experiments involving synthetic N fertilization in the USA Corn Belt and elsewhere, although not with the interpretation usually provided. There are important implications for soil C sequestration because the yield-based input of fertilizer N has commonly exceeded grain N removal for corn production on fertile soils since the 1960s. To mitigate the ongoing consequences of soil deterioration, atmospheric CO(2) enrichment, and NO(3)(-) pollution of ground and surface waters, N fertilization should be managed by site-specific assessment of soil N availability. Current fertilizer N management practices, if combined with corn stover removal for bioenergy production, exacerbate soil C loss.

Comment in

Comment on "The myth of nitrogen fertilization for soil carbon sequestration", by S.A. Khan et al. in the Journal of Environmental Quality 36:1821-1832. [J Environ Qual. 2008]

The over 100 years of data from the University of Illinois Morrow Plots puts in question the idea that we can use synthetic fertilizer as a means of gaining soil organic matter. The idea that propped crop growth under ideal conditions is sustainable has not been verified by long term experimentation. In areas such as Sub Saharan Africa where soil acidity is a real problem and there is no good liming infrastructure the reliance of ammoniated fertilizer will be counter productive. 

Please find work attached from Ethiopia showing 12 of 13 crops of interest showed superior response to compost over synthetic fertilizer. fyi. I reiterate that when drought is the issue the ability to maintain and increase soil Carbon is critical to having good response to rainfed agriculture as the percolation, retention and use of water is increased. All soil before their cultivation have ability to capture over twice that weight in soil which at or over 5% soil organic matter in soils of 1% or less the capacity in terms of water percolation, retention and use is 1/6th that of soil organic matter in optimized soil. Gaining soil organic is definitely proven but not easy what is easy is the fertilizer application but it sustainability that  is the issue especially with farmers of low capitalization. Fertilizers have issues both in their heavy fossil fuel dependency and in their potential to reduce carbon and nitrogen sequestration in the soil itself. The use of agriculture optimized for greenhouse gas emission reduction is important but the big ticket is the enormous potential of agriculture to sequester atmospheric Carbon and Nitrogen which are green house gases contributing to climatic change. This strategy demands a priority given to soil state and secondary interest in application of fertilizers. In fact the over 30 year Rodale Farming Systems Trial show that all the Nitrogen needs for corn and soybean agriculture can be provided by legumes and organic amendment and that after a transition period the yield can equal mean yields in good precipitation years and in drought years the improved soil quality increases the drought yields 25% for maize and 50% for soybean.  These results were achieved by a deliberate effort to eliminate synthetic chemical inputs and depend instead on cover crops, rotations and organic amendment. 

Of course not, preferable using organic fertilizers or compost with chemical fertilizers to reduce hazards of soil