Posts Tagged ‘Soil carbon’

Catch crop effects in a wider context, cover crops.

November 21, 2012

Sweden has since several years a catch crop program. It has been focused on reduction of nitrogen leaching. A compensation is paid to the farmer to encourage the practice.

In previous posts on this blog the more general favourable effect of catch crops, on soil structure, on soil life, on organic matter content has been advocated. It is very encouraging that these issues now are discussed an recognized in an official report.

Catch crops can be transformed to cover crops, where even a harvest can be taken. Also this is mentioned, although the research and experience on this is scant. However,  at least in some favoured areas we can produce a second crop after for instance cereals.  Forage can be preserved as silage and used for biogas,  if  local biogas plants are established. In this way agriculture can substantially contribute to energy production and climate gas improvement.


Agriculture stands for 3% of the economy but maybe 20% of the ecology.

December 15, 2009

 Focus Foresight. This was the start of this blog. Meaning that we both as individuals and farmers need to consider the ecology of the planet. The events this year have not diminished the urgency: climate discussion, ecological limits of the globe etc.

In a conference in Cambridge last week (International Fertiliser Society). Nitrogen Efficiency was discussed. Much can be done to improve the efficiency and reduce losses, for instance precision farming and improved manure management.

But how motivate the farmers? That was not on the agenda of the conference. The farmer acts in a competive market and his main concern is to reduce the costs. In fact, the society has given the farmer one primary goal: produce cheap products. Then – if possible – mind the environment.

There is a way forward: utilize available techniques and knowledge to combine both economic and environmental efficiency. Consider the economy over 4-5 years on your specific farm. Then probably both precision farming and cover crops to improve soil organic matter are positive also economically.

It is interesting to note that the development of crops and cultivars for high yields gives increased importance to maintenance of soil organic matter. 5 tons of wheat can be achieved even with some shortcomings now and then, but for 10 tons top performance is required at every stage. Soil organic matter gives resilience and top performance, and is also positive for environmental function and sustainability.

Better economy and improved environment

June 16, 2009

. Many crop producers have this win-win situation. Check it and catch it. It is about soil organic matter. Or rather, measures promoting soil organic matter and biological activity: harvest residues, green manure, cover crops, organic fertilizers. With cover crops no production year is lost and they can be fitted into most rotations.

Well, this turned out to be some advisory speech, sorry.

But use the soil, use the sun. Let plants pump in carbon, energy and nutrients. Whenever there is an opportunity.

A bare soil means an unused resource (but admittedly sometimes there are reasons).

Use new technology and knowledge. Calculate, see and control. Think ahead.

This is an investment, without cost.

Some days have passed. My posts have been less frequent. But it is not summer lazyness, on the contrary. I am summarizing all knowledge I can get hold of concerning agriculture, soil organic matter, what happens to it and what does it mean. It is almost as a detective investigation. Facts add up, evidence is gathered, relations are explored. But there is a difference: the detective works with what has happened, I work with what is happening. And the result? The case of “taking care of soil organic matter” keeps being strengthened.

Soil organic carbon – continuos losses.

April 23, 2009


Longterm experiments with soil analysis for organic carbon show a decline in soil C for normal crop production also if the straw is returned. The decline is proportional to the level of soil C and seems to attain an equilibrium at about 1% soil C..

This is no favourable development. There are measures: cover crops giving more organic material to the soil, modified tillage, preferably only spring tillage.

On a soil with 1.5% soil C (fairly normal for important agricultural areas) and normal tillage with autumn plowing and straw returned a couple of cover crops can save 200 kg C annually.

There are some costs (seeds etc) but within a few years the increased soil fertility gives higher yields. Also without environmental payment there is some economic gain.

Further, the soil fertility development is secured for the future.

Finally, there are environmental benefits: less greenhouse gases (means more than twice the normal tractor emissions), less nitrogen leaching and reduced erosion.

A triple win-win-win.

Competitiveness – soil carbon – cover crops – zero plots – precision farming – Agrotain.

February 12, 2009


Some topics which have been on the agenda the last few days.

The farmers´ organizations stress competitiveness, thinking of Swedish taxes and environmental rules. They are right, we have a problem. Only – one could wish for a wider view.

A well functioning soil also gives competitiveness. But a yield of 8 tons of wheat must imply a good soil? Maybe so, but it could have yielded 8.5.  Soil carbon helps, more organic material from for instance cover crops is positive for soil carbon and biological activity and also soil structure. There are important advantages to harvest.


Nitrogen is a strong agent – it has to be held in tight reins. With zero plots to characterize the soil and precision farming to adapt to the actual crop you are doing just that. But in for instance England there are other ways of development. Much urea is used which means risks for considerable ammonia losses. These can be reduced by means of chemical substance, an urease inhibitor. Market name: Agrotain. This improves the situation somewhat, but you could ask: is this the best way to go? Wouldn´t it be better to use available knowledge and technology to control the use of reliable N sources as well as possible?


Economy, environment and longterm considerations.

January 28, 2009



From the post below it may seem that these goals don’t go together. It can be so, but not necessarily. Often there are win-win situations and that is the idea behind Farming Perspectives.

An example from a cereal-oilseed farm in middle Sweden:

We use cover crops where possible, which is 3 years of 6. The are left over Winter and all soil management takes place in Spring. On many soils this is possible.

There are costs for seeds and for extra herbicides, say in total SEK 300. But instead there are savings in soil management, maybe 300. This evens out.

The cover crops increase soil carbon in the long term and biological activity directly. This may mean increased yields and income of SEK 100 – 200 for each crop.

With these figures there is a gain of  SEK100-200 per year.


Not very exciting, but something.


And further: Soil carbon is increasing meaning better soil structure, easier management and better yield security.

There will be less risk for erosion and phosphorus outflow.

Nitrogen is kept in the soil and leaching is reduced.

There is more life of all kinds in the soil and the landscape.


Is this idealized? Not in average. In the specific case it depends on the crops, the soil and other farm specific characteristics. And it should be observed that no subsidies or payments are included. They can be added in some areas.


The whole and the details.

January 8, 2009


The Swedish Environmental Protection Agency is arranging a workshop next week in order to squeeze out ideas for further reduction of emissions to The Baltic. That is needed, for large commitments have been made in Baltic Sea Action Plan.


It is about N and P. But I hope that the topic can be widened to include the integrated function of the soil. And that is almost necessary, since we have gone very far in correcting malpractices and errors. Few simple solutions remain. But there are possibilities to improve the functioning of the soil. Better structure, better stability and surface protection will help reducing P outflow. The very work in this direction will also reduce N outflow and greenhouse gases. Biodiversity and yield capacity will increase. Cover crops are more than just N catch crops.

Have a look at my post of 30 Dec.


In general, segmentation and specialization is a problem, both concerning authorities and research. Different units have there own segments. Integration is difficult. The economists should perhaps integrate, but also they have got specialized tasks.


A flower to Greppa Näringen (Focus on Nutrients) who has dared to integrate many aspects in “The soil fertility module”.

Soil fertility and environment. Connections.

December 29, 2008


I am just now working with the following chain of connections.


When soil carbon is low, an increase is positive for soil fertility.

Increase in soil carbon can be achieved by means of cover crops, preferably over-wintering.

An increase in soil carbon improves soil structural stability.

Cover crops not only give raw material for soil carbon, they also provide fresh organic matter which increases soil biological activity, which also is positive for soil structure and fertility.

Soil carbon reacts slowly (decades), biological activity faster (year).

Which means: soil carbon building measures have a positive effect on soil structure both shortterm and longterm.

A more stable soil reduces dispersion in water flow situations and gives lower phosphorus outflow.

A more stable and better aggregated soil gives better infiltration and higher water holding capacity, which tends to reduce both surface runoff and total water outflow.

Less water outflow gives reduced outflow of both N and P.

Cover crops reduce the amount of nitrate in the soil profile and the leaching.

All these links in the chain work together to an end result: measures increasing soil carbon also reduce the outflow of  N and P.


Question marks and counter arguments:


Increased organic matter can increase N outflow. — Yes, but however the future management is arranged there will be a net reduction in total N outflow.


A crop in winter can release soluble P. — Yes, but in field experiments this has not been found. But needs further investigation. A compromise: shallow incorporation late autumn.


Too expensive and troublesome.—  Calculate! How much does a continous decline in soil fertility cost?


Cover crops will lead to more herbicide use. — Maybe. To some extent maybe worth it. To some extent possible to avoid by choice of crops and methods.


And there is another aspect: Greenhouse gases.

If an amount of 200 kg carbon is tied up as soil carbon, 720 kg GHG is tied up, comparable to the emissions when 240 l oil is used.

But this cannot go on for long? No, maybe 30-50 years. But those years may be important.

Nitrous oxide? Varying experimental data. Maybe overwintering cover crop is of advantage.

To plow – or just to sow?

December 6, 2008


Today I have been plowing – in reports on paper and the net. And there was a result: a summary of nordic field experiments about catch crops and soil management.


Usually the question is: Is it really possible to omit the plow? But it seems more relevant to turn the issue around. An answer could be: Maybe the normal autumn plowing works OK in your situation, but experience shows that in most cases some kind of reduced tillage gives higher yields.


This is not a new issue. I remember from the studies in Uppsala during the 1960s I came across a book: Plowman´s folly. It gave me something to think about.


Catch crops – they reduce nitrogen leaching but are also an important factor for soil fertility. Field experiments begin to show that they are positive for soil organic matter and also that in shorter terms (a few years) improve soil structure and soil life.


Both measures save energy and greenhouse gases and interact positively. But they should be used in a way adapted to the soil and the individual farm.






Soil organic matter.

November 28, 2008


Digging through research reports about soil organic matter, its importance for soils and yields, how it is affected by various measures. Some good news:


Cover crops favour soil organic matter. Within a few years advantages for soil structure and yields are evident.


Spring cultivation favours soil organic matter. In addition the nitrogen leaching is reduced.


These relations could be used much more than today.


Some more background:

The soil organic matter (SOM) is a product of long term soil development. The average age in an agricultural soil may be several hundred years. But some minor fractions are young and ephemeral, but their presence and the activity around them are beneficial for the soil structure and function.


Many of our soils should be more fertile and manageable with more SOM. It can slowly be increased by addition of more organic raw material (straw and other residues, green manure) or organic fertilizer. The breakdown of SOM can be reduced by less and later tillage.


The bulk of SOM reacts slowly, it is a matter of decades. But the younger fractions can have more direct influence of the soil function. Danish experiments show that ryegrass cover crops improve soil structure and yields within a few years. In addition nitrate leaching and climate gases are reduced.


A win-win situation, but there are questionmarks for some soils.