Enthusiasts are often frustrated when attempting to intervene in natural systems. Things don't turn out as planned, and the effects of intervention are seldom quick to manifest. I see that a lot when working as an advisor or consultant to others. The interventions that I propose take time and have variable results depending on initial conditions as well as the specific interventions. Over time it is usually necessary to adjust management in response to the effects of previous management. It can look like I'm making it up as I go, and to some extent this is true, but it is more useful to see it as adapative management.

One of the old sayings among growers is that the best fertilizer is the grower's footprints. Fields and swards that are closely observed by principals do better. It can be time consuming but it is time well spent since amendment is adjusted to reflect observations. One day we may be able to delegate that work to sensor networks of some sort, but that day hasn't arrived yet. For the time being the new fangled tech is a supplement to the farmer, in effect making his footprints deeper, more numerous and frequent, rather than a substitute.

Rejuvenating Soil Life Requires Patience

Soil data is "noisy" data. Being a difficult medium to observe and measure, soil has an almost weird capacity to mask change.

In several instances that I can recall, it seemed improvement in soil carbon status was not evident until several years after a change in management was made. The increases in soil organic matter called intervening data into question.

You can see similar data fluctuations due to individual samplers, but this delayed stepping pattern of carbon increase happens a little too often to ignore. It is as if the momentum for an increase in carbon must first collect in the biological dynamic of the soil, invisible to our simple agricultural analysis tools where we measure TKN [Total Kjeldahl Nitrogen], TOC [Total Organic Carbon] and C:N ratios.

The post goes on to quote from a No-Till On The Plains Conference keynote address by Dan Towery, president of Ag Conservation Solutions, which proposed that management regimes such as no-till that seek to massively alter soil should be thought of as goals that may take decades to achieve.

Phase one, initialization, occurs in the first five years. It is where soil structure starts to improve and microbial activity increases. Additional nitrogen is required to do that.

"As organic matter increases, you need the added nitrogen to make more of it," Towery said.

The second phase is transition from the fifth to tenth years. This is when organic matter accumulates, soil aggregation and soil microbial activity elevates, phosphorous accumulates, and nitrogen immobilization and greater mineralization occurs.

Why?

One of the reasons that Dr. Lehmann recommends caution in the use of biochar can be seen in the paper recently published by Christoph Steiner et al., mentioned in previous messages. He did get excellent plant growth responses to adding biochar - as long as mineral fertilizer was also used. When you look at plant growth in the biochar only treatment, growth was worse than doing nothing at all (check plots). In the nutrient-poor and highly leached soils of the tropics, the added biochar likely bound whatever nutrients were present in the soil solution and these became unavailable for plant uptake. These results should make you cautious as well. How fertile a soil needs to be for biochar not to reduce plant growth or exactly how much fertilizer and/or compost should be added to be sure there is good, sustained release of nutrients, will likely vary soil to soil and we simply do not have these data available at present to make proper recommendations. . .

As to the 'wee beasties' or 'critters' as I like to call them, we have made progress on this front over the last several years. Brendan O'Neill and Julie Grossman in my laboratory, Sui Mai Tsai, our Brazilian collaborator at CENA and the University of Sao Paulo, and Biqing Liang, and many others in Johannes Lehmann's laboratory have been characterizing microbial populations in three different terra preta soils and comparing these to the adjacent, unmodified soils near by to them. Brendan found that populations of culturable bacteria and fungi are higher in the terra preta soils, as compared to the unmodified soils, in all cases. Yet, Biqing found that the respiratory activity of these populations is lower (see Liang et al., 2006), even when fresh organic matter is added. This alone means that the turnover of organic matter is slower in the terra preta soils - suggesting that the presence of black C in the terra pretas is helping to stabilize labile organic matter and is itself not turning over in the short term. All good news for C sequestration. However, since the respiratory activity is lower (slower decomposition), this may lead to slower release of other mineral nutrient associated with the fresh organic inputs. In some circumstances this is a good thing (maintaining nutrient release over the growing season), in other circumstances (more immobilization), perhaps not. We need more work on this to understand the implications of these results more fully.

We don't have full knowledge, but in my patch we think of it as needing to feed the 'wee beasties'. The things we do that make soil nicer for them, so that they will in turn make soil nicer for our purposes, causes a population increase. They need to be provisioned in the early days or else they will suffer famine and not increase as we wish.

So, I always recommend adding manufactured fertilizers to swards that are being renovated or improved, even though the end goal is to create swards that do not require such amendment. It is dead common to see enthusiasts dose their fields with manure and get poor growth in response. The fields go into nitrogen deficit since it takes nitrogen to release nitrogen from the manure. Adding char, which is suspected of binding nutrients, seems to have a similar effect. Green manure does the same. Fully rotted and aged compost creates much less deficit, but still tends to increase the 'wee beasties' and so creates a drain on resources at first.

If you do it right, and do it repeatedly, then over time the amount of nutrients needed decreases. There's no magic, you have to see that the nutrients are supplied one way or another, but you can reach the point where manufactured fertilizers are seldom if ever needed. You pay a price for this, there's no free lunch, since the things you must do to avoid manufactured nutrients have costs. If you don't import fertility in some form then it must be created on site, and this reduces net output. One way or another you pays for your pleasure.

Given world needs for productivity it is arguable that the price is too high. More production is needed from limited land and water supplies. The best practice appears to be a combined system that takes pains to create the healthiest soils, which need less imported fertility to yield spectacularly, but which do better when nutrient supplements are applied.