Weeding Reduces Both Water Loss And Slug Movement

We talked last year about the virtues Dutch hoeing.

SEALS IN WATER
Now, after the recent rains, when the weed seeds in the soil have germinated but not yet seeded, is a perfect time to use a Dutch hoe. Loosening the top half inch (2.5cm) or so of soil will not only kill weeds, but will also break the wicking (capillarity) link between the soil surface and lower layers, thus creating an effective mulch which will both insulate the soil and greatly reduce water loss - it effectively seals the water in.

REDUCES SOIL TEMPERATURE
Loose, airy soil dries very quickly and lightens in colour. Thus, more of the sun's heat is reflected; and what is not reflected cannot conduct down through the loose soil as easily. Hence, the roots can work more effectively.

CONTROLS SLUG MOVEMENT
Slugs do not like moving over loose, dusty surfaces which stick to them, preferring wet conditions. You will notice the difference immediately - they seem to completely disappear. However, they soon return once the surface is wetted again . . . more's the pity.

Potato Surface Root Proliferation

Over the past week or so, fine curly roots have proliferated just beneath soil surface (some are ringed red). However, it's not clear where these are originating. And this activity seems to be mostly above troughs in main root wave. But where main root comes closer to surface, there is little sign of it (right). Although these new roots are clearly visible through side of pot, they cannot be seen from above. i.e. they do not seem to penetrate soil surface.

PURPOSE OF ROOTS
Not sure what purpose these roots serve, but presumably they gather water from light rain showers, which hardly penetrates into soil. Should think they can also extract condensation formed overnight at soil surface from water vapour rising from below. Probably quite a lot of water to be had this way.

Had no idea potatoes were so efficient at extracting water (if that's what these roots are for). But concerned about:

• what happens if surface dries out - do roots survive and remain effective?
• what happens when roots disturbed by surface weed control - how quickly do they re-grow, if at all?
• what happens when potatoes earthed up - how quickly can they reach new surface?
• do they make mulching less effective (not so much in potatoes but in other crops)?
• implications for top dressing

WHEN SURFACE DRIES OUT
Very few commercial soils have constantly damp surfaces. Are these roots damaged by drying? Presumably not - not if their purpose is to harvest rare showers in dry soil.

WEED CONTROL
Surface hoeing could be a real problem and present much damage, at least in the short term. But most of weed control in potato drills is done by covering small weeds during 'earthing up' process. Would seem essential not to let weeds get too large to be covered this way.

MULCHING - IS IT ALWAYS EFFECTIVE?
Because mulching materials tend to be coarser than soil, it's likely these roots cannot proliferate to same extent, if at all, perhaps leaving a dry barrier between soil surface and atmosphere - one which light rain showers could not penetrate.

As already outlined, if the top couple of centimetres (inch) or so of soil surface is loosened by cultivation it forms a natural barrier (mulch) to water loss (see posts on weeding and water conservation). Therefore, all mulching really does is delay the drying process; it is probably not much more effective than the soil's own natural mulch (formed when loosened surface insulates and reduces loss due to wicking). Bearing in mind surface roots, we need to ask the question: 'Are there are circumstances where mulching might be ineffective?'

TOP DRESSING
It's always assumed feeds need working into surface. Might do more harm than good.

Any views about all of this?