When prospection rhyme with agriculture

(DETECTION & ARCHEOLOGIE N°3)

Many are the prospectors who in the course of prospection request from their colleagues nature cultures that one meets in the fields.

Briefly, I propose to you a panorama of the cultures most commonly met. Indeed, I think that a better knowledge of these cultures, and especially of the periods of occupation of the grounds will make it possible to the prospector to be more attentive and to project outputs (obviously!).

Note:

The dates indicated are not that forks they are valid for a perimeter of 100 km around Paris and for the Centre area. Obviously, these dates vary with the climatic conditions at the time of sowing and harvest (of precipitations work blocks).

The cultures such as beets, corn, pea, colza are called " heads of rotation " because they always precede the culture by a cereal (barley, corn....). In general, rotations of cultures are always rotation-corn-barley head but those can be modified according to market and the practice prices of the fallow by the farmer.

The corn, the beets, the peas is cultures of spring because sowings proceed for this period.

If you decide to prospect after harvest:

In all the cases, it is to better await a passage of tools for désocler the residues of cultures (désocler = " to plough the stubble") then the ground levels will be more pleasant to prospect.

Attention at the periods of hunting in plain 25/09-30/02; you show vigilant if you prospect one Saturday or Sunday morning.

Often the grounds are rather dry preventing an optimal detection because they are less conducting (in this case prefer a wet ground)

Politely ask for the authorization of prospection to the farmers and do not detect in a sown field.

CULTURES	Go back to sowing	Go back to harvest	Tillage before sowing	Advantages
Corn (cereals)	15/10-10/10	10/07-10/08	End with wheatear	Pleasant to prospect (sometimes sticking grounds)
Barley of Spring (cereal)	15/02-30/02	20/07-10/08	Wheatear	Well but cold time
Barley of winter (cereal)	05/10-15/10	30/06-10/07	End with wheatear	Pleasant but attention the perhaps sown field (risk of confusion)
Beets (industrial culture)	15/03-25/03	25/09-20/11	End with very fine	Very pleasant to prospect
Corn (cereal)	05/04-10/04	10/10-10/11	End with very fine	idem
Colza (oleaginous)	20/08-10/09	30/06-20/07	End	idem
Pea (protéagineux)	15/03-25/03	10/07-30/07	End with coarse	To prospect well

Definitions of the words of the technical terms used previously:

- Rotation of crops: Succession of the cultures on a given plot of land.

EX: Beet-Corn-Barley-Beet-Corn-Barley-etc...

The Rotation of crops finds its justification in the fight against the ravageurs of the cultures. The principle being of alternating the cultures to limit the progression of the ravageurs. Nevertheless, in certain areas, one practises on the contrary monoculture (in the Moors with corn), these practices make necessary the use of great amounts of plant health products ("literally which clean the plants and protect them from the ravageurs") to thwart the year development by year of the ravageurs specific to the culture.

Because in the case of monoculture, owing to the fact that the culture is the same one year by year, the ravageurs which are in the ground (mushrooms, insects, many invertebrate.) increase in a number year by year (of or the products phyto!)

Rotations can be modified in function:

- economic context of production (more or less profitable production)

- area (overall according to the microclimate of the area)

- agronomic potential of the grounds (the sugar beets rather appreciate the deep grounds with strong hydrous reserve like the clay soils or the silts)

- orientation of the system of production of the farm (rather breeding or field crops)

- rate of fallow imposed to the farmer (the farmer should not cultivate certain pieces any more during a given time and a given surface)

Generally, principal rotations in our areas are:

- Pea-Corn-Barley

- Colza-Corn-Barley

- Beet-Corn-Barley

- Corn-Corn-Barley

Which information for us prospectors '

Being given that one knows the succession of the cultures (rotations) and dates of establishment a priori of these cultures (see table preceding page), we can envisage our outputs in advance.

Indeed, the establishment of the cultures (sowing) requires beforehand a ploughing, a harrowing; the ground coldly stirred up there at this time awaits nothing any more but one blow of frying pan!

Attention however not to confuse a prepared field and an actually sown field!

A sown field is distinguished very well with traced furrows.

S.DEVANLAY.