“Not for wheat,” said I. “But if you seed the wheat down with clover, as would be the case in this section, we should get considerable benefit, probably, from the guano. If wheat was sown after the wheat, the guano applied the previous season would do little good on the second crop of wheat. And yet it is a matter of fact that there would be a considerable proportion of the guano left in the soil. The wheat cannot take it up. But the clover can. And we all know that if we can grow good crops of clover, plowing it under, or feeding it out on the land, or making it into hay and saving the manure obtained from it, we shall thus be enabled to raise good crops of wheat, barley, oats, potatoes, and corn, and in this sense guano is a ‘lasting’ manure.” “Barnyard-manure,” said the Doctor, “is altogether too ‘lasting.’ Here we have had 56 tons of manure on an acre of land in four years, and yet an acre dressed with 500 lbs. of guano produces just as good a crop. The manure contains far more plant-food, of all kinds, than the guano, but it is so ‘lasting’ that it does not do half as much good as its composition would lead us to expect. Its ‘lasting’ properties are a decided objection, rather than an advantage. If we could make it less lasting--in other words, if we could make it act quicker, it would produce a greater effect, and possess a greater value. In proportion to its constituents, the barn-yard manure is far cheaper than the guano, but it has a less beneficial effect, because these constituents are not more completely decomposed and rendered available.” “That,” said I, “opens up a very important question. We have more real value in manure than most of us are as yet able to bring out and turn to good account. The sandy-land farmer has an advantage over the clay-land farmer in this respect. The latter has a naturally richer soil, but it costs him more to work it, and manure does not act so rapidly. The clay-land farmer should use his best endeavors to decompose his manure.” “Yes,” said the Doctor, “and, like John Johnston, he will probably find it to his advantage to use it largely as a top-dressing on the surface. Exposing manure to the atmosphere, spread out on the land for several months, and harrowing it occasionally, will do much to render its constituents available. But let us return to Mr. Lawes’ wonderful experiments.” “On eight plots,” said I, “300 lbs. of ammonia-salts were used without any other manures, and the _average_ yield on these eight plots was nearly 26 bushels per acre, or an average increase of 9 bushels per acre. The same amount of ammonia-salts, with the addition of superphosphate of lime, gave an increase of 13 bushels per acre. 400 lbs. ammonia salts, with superphosphate of lime, gave an _increase_ of nearly 16 bushels per acre, or three bushels per acre more than where 14 tons of barn-yard manure had been used four years in succession.