Disappointment will result from the application of lime, marl, salt potash, guano, or any special and highly concentrated substance as a fertilizer, to the neglect of organic manures. We lay down this fact as incontrovertible, that no soil, however fertile it may be made for the time being by any of these special manures, can remain permanently so, unless care is used to maintain a healthful supply of organic matter,--rich mould--good soil upon the land cultivated. If this is done, we never shall hear of guano failing to bring increased crops or of the "land running out," where it has been applied. Special manures of any kind may fail to produce crops, where this essential requisite to good farming is neglected. Guano, in our opinion, should always be followed by crops of clover, grass, peas, or some crop that will shade the earth, and can be turned under with the plow, to keep up the necessary supply of nitrogenous food for cereal crops. _The effect of Lime and Salt_ upon land is to _dissolve_ the inert portions of organic matters in the soil, so that plants can suck up their substance into their own composition. Both are highly beneficial, but insufficient to add permanent fertility. _The effect of guano_, is greater than any other highly concentrated manure ever discovered and applied to any soil. Its benefits are immediate continuous, and unlike lime, without exhausting the soil of its organic matter. Yet its benefits will be increased by the addition of organic manures derived from green crops, straw, or the stable, and the value of these will be greatly increased by the addition of lime, salt and plaster, while any deficiency of phosphates must be supplied by powdered bones or another application of guano. _The effect of plaster with guano_ is to arrest the excursive disposition of the volatile parts of the guano, and imprison them in the earth until called forth by the growing plants to do the State some service. The following question to the Editor of the American Farmer, and his reply, are to the point in this matter:-- A correspondent says--"As to the question of mixing plaster with guano, there is one question I should like to propose to the editor, viz.--'what will be the effect of sowing guano upon land by itself, and then, the seed being in the ground, giving it a heavy top-dressing of plaster, so as to arrest the 'excursion,' of which so much is said?"