If our correspondent would _mix_, in the proportion of 200 lbs. of _guano_, one bushel of _charcoal_, and half a bushel of plaster per acre, and sow the mixture on his wheat field next spring, after the frost is entirely out of the ground, then seed each acre with clover seed, and roll his land, we have no doubt that his wheat crop would be increased five or six bushels to the acre, perhaps more, and that he would have a good stand of clover plants, and a luxuriant crop of the latter next year. "Our opinion is, that _guanoed_ land should always be sowed to clover, or clover and orchard grass." In this, particularly the opinion of the last paragraph, we fully concur--to obtain the full value of guano it must either be mixed with plaster or charcoal, or what is better, plowed in and thoroughly incorporated with the soil, and the land always sown with clover, peas or some other plant of equal value for green manure. It is true Col. Carter has been successful with wheat after wheat; while many continue successful, by carefully retaining all the straw; the guano being sufficient to keep up the everlasting ability of the soil to produce an annual crop of grain. THE FIVE FIELD SYSTEM AND GUANO. We look upon this as the most preferable of all other systems of farming ever adopted in the South--it is the system of Edmund Ruffin, to whom Virginia owes a debt of gratitude beyond her power to pay. It will be seen from the following extract from a letter of Mr. Newton that that eminent agriculturist is of opinion that improvement of poor land is unlimited, if guano in connection with this system is perseveringly applied. He says--"The "five field System," which is now rapidly extending over all the poor and worn lands that are now under improvement by marl, lime, or guano, originated, or at least was first extensively introduced in lower Virginia, on the Pamunkey, and has there wrought wonders, aided by marl and judicious farming. The rotation is corn,--wheat,--clover--wheat, or clover fallow,--and pasture, and after pasture one year, commencing the round again with corn. This system, if guano be applied to both crops of wheat, on corn land and fallow, or alternately with lime or marl, when calcareous manures are required, will readily increase the crops and permanent improvement of the land. In the commencement of the rotation, lime had better be applied with the putrescent manures to the corn crop, to be followed by guano on wheat. If this system be perseveringly, pursued, I can scarcely see any reasonable limits to the improvement of poor lands and the increase of the profits of agriculture."