Wet on Top, Dry Underneath

WET ON TOP

DRY UNDERNEATH

However, now that we're at the end

What if I said, that it’s the same root cause that produces both drought and flooding? That your farm, whether it be cropping or grazing, organic or conventional can be reworked to be both drought-proof and immune to extreme rain events. Sound too good to be true? Well read on. If it’s not there when it’s wet, it’s not there when it’s dry First we better rewind a few steps and show so how it is that a single causal factor is responsible for droughts and flooding.

This single causal factor means that on the one hand (in 2018) we were feedingout first-cut silage and achieving little or no grain-fill and this winter we ended-up with maize harvests that looking like the Written by Niels Corfield The winter of 2019/20 has been battle of the Somme (reparable but not the surface of these soils that was at challenging for farmers to say the least. good optics). capacity, the bulk soil was dry, often Incessant rain meaning fields were not accessible, and winter crops were not sowed, large areas of flat or low lying Management Dictates Infiltration very dry. See soil pictured below for an illustration. country flooded (sometimes repeatedly) Above we see two spade sample of the and otherwise generally redefining the same soil type on the same day, margin concept of mud. on the left and grazed pasture, recently

of 2020, how's the ground shaped up Simply put the causal factor is a lack over the year? Did the moisture seem of infiltration (or low infiltration rates) in to disappear, even after the wet winter all but the lightest or stoniest of soils — of 2019-20? When the ground across and a lack of retention in these soils. The the farm (and the country), it seems, water that falls as rain has only one of was saturated. two places to go it can either go into-

reseeded. (and through) the soil or away as runoff.

If your soil it’s very light or naturally free draining that water will go straight through, and in heavier soils that water will run-off. In both cases that water has left and has not been retained within in the soil profile.

But our soils were clearly saturated this winter, I hear you say! How can you be suggesting there’s a lack of infiltration?

Well, the experience is, that it’s

Time to Infiltrate 1″ of Water: 7 seconds (field margin, at left) — 20+mins Soil Sample: well hydrated in top 2″, dry below. Standing water and loamy soils.

You’ve got one chance, and one chance only, to get the water into your soil and that’s when it rains, as infiltration.

Without infiltration that water will run off. It’s a simple choice where would we prefer to have are rainfall: in the soil where it can grow crops and forage, or in the valleys where it fills up like a bathtub: damaging property, and causing travel disruption and economic impact?

It seems counter-intuitive to say we want more water in our soils, given the experiences of winter we’ve just had. Surely, all that mud and saturation wants to be mitigated, by drainage or other means?

Well, no, in a word. What we looking for is deep penetration into- and through the soil profile. Structure So what does this mean? What is this indicative of?

Simply that these soils lack pore space. They often are blocky and

consolidated and largely just structured in their “native”, mineral state (where all the soil particles are bonded to each other, in a tight crystalline state). These bonds are strong, but brittle, so when they fail, they may well “cleave” along fault lines, revealing: cracks, jagged edges and angular shapes.

At the landscape scale what features do we associate with these terms (and shapes)?

Generally: cliffs, rock faces, and mountains. And what is the study of these materials and these types of features? It’s geology.

Simply put, if your soil looks and behaves like geology: it shatters, cracks or cleaves, has the appearance of rocks or stone, it is geology.

Which makes sense because the sand, silt and clay is basically just ground up rock. However, when we refer to soil that’s just sand, silt and clay, it’s subsoil (in old money). Fundamentally, the difference between subsoil and topsoil is that topsoil is subsoil that has been acted upon by biology.

And what is biology’s influence on the soil structure? Primarily the creation of pore space. Converting the soil from its native, homogeneous state where the soil particles “pack” readily, into to a heterogeneous state, binding together disparate soil particles into crumbs or “aggregates” with a network of internal voids running between them.

Just as a biscuit maker converts base ingredients, flour and sugar, into crumbs with the addition of a binding agent, like butter. Where the flour and sugar particles are effectively the same size as one another but once the binding agent is added those crumbs that result now have a large variation in size, from something like a bowling ball down to a golf ball.

In the case of the soil, our sugar is analogous to sand (coarse, granular), while the clay is analogous to flour (since if you purchase dried clay it comes bagged, as a powder). In soil, the aggregates are bound together by sticky substances like polysaccharides (carbohydrates) that are secreted by organisms like bacteria. In the same way that if you’ve ever got slug trail on your clothing it goes on sticky, cannot easily be washed off and sets hard, in other

Pasture vs Covered Arable vs Bare Arable (Photo: LSU AgCenter) words these compounds are glue-like in nature.

So, we can say that soil aggregates are literally glued together by the secretions of biology.

This is what gives boy soil it’s friable crumbly and easily workable texture.

Fundamentally it’s this crumb structure and the pore space that facilitates infiltration. Over and above what the native soil does alone.

Moreover, with light soils these crumbs increase the surface area and with-it water holding capacity making them more moisture retentive. Since these surfaces of the aggregates are places where water films form. And it’s these billions of tiny water films throughout the soil volume that gives it its water holding capacity.

In heavy soils the opposite is the case, it serves to make the soil more free-draining. By opening up the dense structure and introducing pore spaces. Spaces that are interconnected, through which rainfall can easily percolate whilst also collecting around the aggregates as water films.

In both cases this forms a water reserve that can be drawn upon by crops and forages in the sunny, warm periods that are optimal for growth and grain fill.

So, with the exception of a small number of self-aggregating soils, crumb structure is entirely a product of biological activity and an expression of the carbon cycle in action, as these are carbon-based compounds, derived from plants, often root exudates (sugars).

It’s these processes at play in the above example comparing margin with reseeded pasture Management Determines Infiltration Rates So, what you can do, how can you achieve this friable structure without necessarily going to grass? Simply put, apply the soil health principles at every stage of your cropping and management practices Pasture vs Covered Arable vs Bare Arable (Photo: LSU AgCenter) Simply put here in the UK we are not victims of either too much or too little rainfall, just inadequate infiltration or retention. In a cropping situation it’s not only the lack of pore space but also surface capping (from rainsplash etc) As Yoda says: “Hmm, not how much rains it matters, how much we retain, it does.” So in one fell swoop by fixing infiltration we not only do ourselves a favour: eliminating muddy conditions and poor field access options early and late season, we also optimise production through seasons like 2018.

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DRILL MANUFACTURERS IN FOCUS...

FOCUS TD OFFERS STRIP-TILL IN NEW 3M WORKING WIDTH

HORSCH has launched a 3m version of the proven Focus TD strip-till line to offer a solution for smaller operations to combine strip tillage and sowing.

Following customer requests for a smaller machine, the 3m model has a steel hopper with 3500 litre capacity with a partition of 60:40. In addition, a MiniDrill with an additional 400 litre capacity is available. MiniDrill increases productivity The MiniDrill offers a third component in the application process and increases the productivity of the machine. In the case of OSR seeding, the rape seed can be metered with the MiniDrill and the two main hoppers can be used for fertiliser, increasing the seeding output of the Focus by 40%. If the MiniDrill is used as an addition to the PPF system, the seed outlets are located in the seed bar area and can be used to apply slug pellets, for example.

The Focus TD has been designed to be an uncompromising solution for strip and conventional drilling in one machine. The TerraGrip tine system creates a deep loosened area and fertiliser can be placed shallow, deep or 50/50. The tine cultivation frame can be replaced with the DiscSystem to create a compact rotary disc harrow. Further options As an additional choice to the wellproven TurboDisc double disc coulter, the new TurboEdge tine coulter can be specified. It is suited to row spacings that are larger than 25cm for rape and beans. Especially suited to heavy soils or those with a lot of residues on the surface, the seed tine offers exact placement of the seed. Even if there is limited cultivation work, the TurboEdge coulter shows its advantages. In other conditions, the TurboDisc coulter continues to be the best choice for optimum precise seed placement.

A crumbling unit, instead of the levelling discs, in front of the packer provides a fine earth in the seed strip and is particularly effective on medium and heavy soils. Due to its open design and small diameter, coarse soil is easily crushed and the self-cleaning effect on sticky damp soils is excellent.