1876.] 
AMERICAN AGRICULTURIST. 
249 
pan of sheet iron 30 inches long, with the other 
parts in the proportion shown in figure 3. The 
edges of the pan curve inward and make it difficult 
for the insects to crawl out. With this in one hand,' 
and a light brush in the other, one can knock off - the 
insects in large numbers very rapidly. The brush 
should be stiff enough to remove the larvae and not 
Fig. 3.—PAN FOR CATCHING BUGS. 
injure the leaves; we find a wisp of straw, or a 
bunch of some strong growing grass, as handy as 
anything. There are patented contrivances for 
mechanically removing the bugs, but they promise 
no better results than these simple means. 
SHALL WE USE POISONS ? 
If the means already suggested are insufficient, 
we say emphatically, yes. Use Paris green. We 
gave last month on page 207, very concise direc¬ 
tions for the “Buying, Using, and Keeping” of the 
poison. Those who would read more on this arti¬ 
cle are referred to June of last year, p. 236, and 
August last, p. 291. “ But it is dangerous.”—Yes, 
and so are fire, gunpowder, razors, and several other 
things, very dangerous in the hands of children and 
stupid people. Knowing it to be deadly, treat it 
accordingly. 
CAUTION AS TO OTHER POISONS. 
Several potato-bug poisons are offered, the com¬ 
position of which is kept secret. Some of these 
arc white, others artificially colored. We doubt if 
these possess any superiority over Paris green. 
We have had complaints that some of these are 
entirely inert. Paris green is perfectly effective, 
we know exactly what it is, and how dangerous it 
is, and we feel safe in giving the advice not to give 
up a thing that we know, for some secret compound 
the composition of which we do not know. 
Science Applied to Farming—XIX. 
BY ritOF. W. O. ATWATER. 
Feeding Plants.—Field Experiments xvitli 
Fertilizers—Wants of Different Soils.— 
Economy in Manuring. 
An intelligent farmer visiting our Experiment 
Station, and examining some fertilizers we had an¬ 
alyzed, asked “ which were the better fertilizers, 
phosphates or potash salts ? ” The reply was, and I 
knew no better one : “Potash salts where potash is 
needed, phosphates where phosphoric acid is need¬ 
ed, and nitrogenous manures where nitrogen is 
needed. Stable manure is a ‘ complete ’ fertilizer, 
it furnishes all that the plant needs for food, and 
improves the soil in other ways also. Now if you 
have not enough of this, and are going to buy com¬ 
mercial fertilizers, it is perfectly clear that you 
ought to select those which furnish what your land 
and crops most need. It will do little good to put 
potash salts on lands that contain an abundance of 
available potash, or phosphates where plenty of 
phosphoric acid and lime are at hand. And if ni¬ 
trogen, and phosphoric acid, and potash, are all 
lacking, neither the phosphates nor the nitrogenous 
manures, nor the potash salts, will alone suffice. 
But it is certainly poor economy to either add fer¬ 
tilizing materials to a soil which furnishes them in 
abundance, or omit others for which crops are suf¬ 
fering. At the same time, if you do not know 
what your soil lacks, and feel that you must do all 
you can to make sure of a crop, and enrich your 
land at the same time, use your nitrogenous super¬ 
phosphates, and German potash salts together. 
The former will furnish nitrogen, phosphoric acid, 
sulphuric acid, and lime; the latter, potash and 
magnesia. Thus you will have a fertilizer with all 
that the plant needs, a complete manure. At the 
same time it is well to remember that you may feed 
your crops, not only directly by giving them these 
ingredients in guano, phosphates, potash salts, and 
so on, but iudirectly by rendering stores of plant- 
food, present in the soil or atmosphere, available 
through tillage and the use of cheaper fertilizers. 
A little lime or plaster may sometimes be thus more 
valuable than an amount of phosphates or potash 
salts that would cost several times as much.” 
Feeding Plants and Enriching Soils. 
In a conversation between a number of our best 
Connecticut farmers a few days ago, one of them 
made a remark which seemed to me very much to 
the point. He said, “ We farmers are just begin¬ 
ning to get into our heads the idea that we must 
feed our plants as we feed our animals. We have 
always had the notion that to get good crops we 
have simply to make our soil rich, and have not 
stopped to think how the manure helps the plant 
to grow. But we have got to learn that the use of 
fertilizers is to feed our plants, and that we must 
adapt them to the needs of our crops, just as we 
adapt the fodder to the wants of our stock. We 
have got to learn how to make the most of the 
plant-food that our soils may furnish of themselves, 
and to supply in manures what our soils lack.” 
The truth and force of these remarks, and par¬ 
ticularly the variations in different soils as regards 
lack of plant-food is very finely illustrated in a 
comparison of the results of the 
Field Experiments 
of Messrs. Lawes and Gilbert in England with those 
performed by Prof. F. H. Storer, at the Bussey In¬ 
stitution, at Jamaica Plain, Boston, Mass. 
As many readers know, the field experiments of 
Messrs. Lawes and Gilbert are by far the most elab¬ 
orate that have ever been made. They have con¬ 
sisted in raising different crops with different ma¬ 
nures, the same crop being grown on the same plot 
of land with the same manure year after year for a 
long series of years. In an experiment with barley, 
for instance, a field of about ten acres was divided 
into some 28 plots, which were treated with differ¬ 
ent kinds of fertilizers. The experiment was be¬ 
gun in 1852, and has continued until now, each in¬ 
dividual plot receiving the same manure year after 
year. A similar experiment with wheat has been 
going on for over thirty years. Others have been 
tried with grass, clover, turnips, and so on. Dur¬ 
ing all this time each crop of each experiment has 
been carefully gathered, and its amount and char¬ 
acter noted. In a letter to the Treasurer of the 
Massachusetts Society for Promoting Agriculture, 
dated March 25, 1873,* Mr. Lawes gave a “ summa¬ 
ry which may be said to comprise the results of my 
experience and practice in regard to artificial ma¬ 
nures for the last thirty years. ” In this he says 
that “the only two substances really required in 
artificial manures are : 1st. Nitrogen. 2nd. Phos¬ 
phate of lime. . . . The best possible manure 
for all graminaceous crops—wheat, barley, maize, 
oats, sugar-cane, rice, pasture, grass—is a mixture 
of superphosphate of lime and nitrate of soda. 300 
pounds of superphosphate of lime and 275 pounds 
of nitrate of soda, applied every year to one acre 
of ordinary English land, has for twenty consecu¬ 
tive years given a produce annually of six quarters 
(48 bushels), of barley. Fourteen tons of farm¬ 
yard dung applied annually over the same period, 
has given the same produce of barley. . . . 
Potash is generally found in sufficient quantities in 
soils, and the artificial supply is not required.” So 
much for the results of Messrs. Lawes and Gilbert’s 
investigations. Now let us turn to 
Prof. Storer’s Experiments. 
These were conducted on the same general plan 
as those of Lawes and Gilbert, though the details 
were different. The plots were smaller, about one 
rod square each, and they have continued only four 
years. The soil was light, dry, and of itself not 
very productive, while that of Lawes and Gilbert 
was moist and strong enough to yield without ma¬ 
* Bulletin of the Bussey Institution. Part II, 1874. 
nure an average of 20 to 22 bushels of barley per 
acre for 20 years in succession. The motive of 
Prof. Storer’s experiments was “ to determine, if 
possible, what kinds of fertilizers, among those or¬ 
dinarily obtainable in Boston, are best fitted to in¬ 
crease the yield of crops grown upon a field that 
had been chosen as a typical representative of the 
thin light ‘ leachy ’ soils which so frequently over- 
lie the gravelly drift in New England.” Three 
kinds of crops, barley, beans, and ruta-bagas, were 
grown. Over 280 plots in all were cultivated. Yard 
and stable manure, muck, fish-scraps, bone-meal, 
superphosphates, salts of ammonia, potash and 
soda, lime, ashes, and other fertilizers were used. 
In general, the manures which contained consid¬ 
erable potash yielded the best crops, while phos¬ 
phates and nitrogenous manures did but little good, 
and in some cases positive harm. The largest crops 
were obtained with dung and with wood ashes. 
Nitrate, sulphate, and carbonate of potash (pearl 
ash) likewise brought large returns. In a summary 
of comparative results, wood ashes proved more 
efficacious than any other single fertilizer, the yield 
being larger than with either yard or stable manure. 
Prof. Storer concludes that the soil of his exper¬ 
iments needed potash rather than phosphoric acid 
or nitrogen. “The addition of potassic manures 
to the soil manifestly enables the crop to make use 
of a certain store of phosphoric acid and nitrogen 
which the land contains. It is clearly shown, more¬ 
over, that the amount of available potash in the 
soil must be very small, since neither the phosphatic 
nor the nitrogenous manures by themselves, nor 
mixtures of the two, such as several of the super¬ 
phosphates are known to be, could enable the crops 
to get enough potash from the soil to keep them 
from starving after the first year.”—And further : 
“ It is plain that the soil of this field, like those of 
thousands in New England, needs fertilizers that 
are rich in potash, and that, under the existing 
condition of tilings, no advantage can be gained by 
applying mere phosphatic and nitrogenous fertilizers 
to the land. . . . If only potash enough be given to 
this soil, the latter can of itself supply all the other 
ingredients that compose the food of plants, at 
least for the term of years during which the exper¬ 
iments lasted, and for as many more, of course, as 
the store of phosphates and nitrogen may hold out. 
. . . The crying want of the land is for potash, and 
potassic manures should be applied to it to the well 
nigh exclusion of all other fertilizers until an equi¬ 
librium is reached.” 
Here are conclusions from experiments made in 
two different places and on two different kinds of 
soil. They agree in showing that the soils were 
able to furnish enough of all the ingredients of 
plant-food to yield small crops and enough of cer¬ 
tain ones, to produce crops of considerable size, so 
long as the other ones which were lacking were 
supplied. But in Lawes and Gilbert’s experiments, 
potash did but little good, while nitrogen and phos¬ 
phoric acid were most efficient. The soil supplied 
enough potash provided the lacking nitrogen and 
phosphoric acid are added. In Storer’s Experiments, 
on the other hand, potash was more needed than 
anything else, and the manures that contained pot¬ 
ash were the only ones that did much of any good. 
Any readers who are interested in the details of 
these experiments, can find the original accounts 
of those of Lawes and Gilbert in the various vol¬ 
umes of the Journal of the Royal Agricultural So¬ 
ciety of England, and of Prof. Storer’s in the Bulle¬ 
tins of the Bussey Institution. Meanwhile allow 
me to point to a few 
General Conclusions 
to be drawn from the facts and experiments briefly 
referred to in this and preceding articles. Though 
the words are my own, the ideas are those not only 
of the men who have made the experiments, but of 
others who have, in various ways, on the farm and 
in the laboratory, made the study of these subjects 
their life work, and whose opinions are worthy of 
our most respectful consideration. 
The wants of different soils, and of different crops 
as well, are very different. Economy in farming 
requires that these wants should be learned and 
