WET ON TOP DRY UNDERNEATH Written by Niels Corfield
The winter of 2019/20 has been challenging for farmers to say the least. Incessant rain meaning fields were not accessible, and winter crops were not sowed, large areas of flat or low lying country flooded (sometimes repeatedly) and otherwise generally redefining the concept of mud. However, now that we're at the end of 2020, how's the ground shaped up over the year? Did the moisture seem to disappear, even after the wet winter of 2019-20? When the ground across the farm (and the country), it seems, was saturated.
battle of the Somme (reparable but not good optics).
Management Dictates Infiltration
the surface of these soils that was at capacity, the bulk soil was dry, often very dry. See soil pictured below for an illustration.
Above we see two spade sample of the same soil type on the same day, margin on the left and grazed pasture, recently reseeded. Simply put the causal factor is a lack of infiltration (or low infiltration rates) in all but the lightest or stoniest of soils — and a lack of retention in these soils. The water that falls as rain has only one of two places to go it can either go into(and through) the soil or away as runoff.
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.
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
DIRECT DRILLER MAGAZINE
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
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? Time to Infiltrate 1″ of Water: 7 seconds (field margin, at left) — 20+mins
Simply that these soils lack pore space. They often are blocky and www.directdriller.co.uk 37
