Talks on Manures Part 41

Table Showing the Amount of Nitrogen Recovered, and Not Recovered, in Increase of Produce, for 100 Supplied in Manure.

----+-----------------------------------------+--------------------- For 100 Nitrogen P in Manure l Manures Per Acre, Per Annum. +----------+---------- o Recovered Not Rec'd t in in s Increase. Increase.

----+-----------------------------------------+----------+---------- Wheat--20 Years, 1852-1871.

----+-----------------------------------------+----------+---------- 6 Mixed Mineral Manure and 200 lbs. Ammonia-salts (= 41 lbs. Nitrogen) 32.4 67.6 7 Mixed Mineral Manure and 400 lbs. Ammonia-salts (= 82 lbs. Nitrogen) 32.9 67.1 8 Mixed Mineral Manure and 600 lbs. Ammonia-salts (= 123 lbs. Nitrogen) 31.5 68.5 16 Mixed Mineral Manure and 800 lbs.[1] Ammonia-salts (= 164 lbs. Nitrogen) 28.5 71.5 9A Mixed Mineral Manure and 550 lbs.[2] Nitrate Soda (= 82 lbs. Nitrogen) 45.3 54.7 2 14 tons Farmyard-Manure every year. 14.6 85.4 ----+-----------------------------------------+----------+---------- Barley--20 Years, 1852-1871.

----+-----------------------------------------+----------+---------- 4A Mixed Mineral Manure and 200 lbs. Ammonia-salts (= 41 lbs. Nitrogen) 48.1 51.9 4AA Mixed Mineral Manure and 400 lbs. Ammonia-salts (= 82 lbs. Nitrogen) 49.8 50.2 6 years, 1852-'57 Mixed Mineral Manure and 200 lbs. Ammonia-salts (= 41 lbs. Nitrogen) 10 years, 1858-'67 Mixed Mineral Manure and 275 lbs. Nitrate Soda (= 41 lbs. Nitrogen) 4 years, 1868-'71 4C Mixed Mineral Manure and 2000 lbs. Rape-cake (= 95 lbs. Nitrogen) 36.3 63.7 6 years, 1852-'57 Mixed Mineral Manure and 1000 lbs. Rape-cake (= 47.5 lbs. Nitrogen) 14 years, 1858-'71 7 14 tons Farmyard-Manure every year. 10.7 89.3 ----+-----------------------------------------+----------+---------- Oats--3 Years, 1869-1871.

----+-----------------------------------------+----------+---------- 4 Mixed Mineral Manure and 400 lbs. Ammonia-salts (= 82 lbs. Nitrogen) 51.9 48.1 6 Mixed Mineral Manure and 550 lbs. Nitrate Soda (= 82 lbs. Nitrogen) 50.4 49.6 ----+-----------------------------------------+----------+----------

[Note 1: 13 years only, 1852-1864.]

[Note 2: 475 lbs. Nitrate = 71 lbs. Nitrogen in 1852; 275 lbs.

= 41 lbs. Nitrogen in 1853 and 1854; 550 lbs. = 82 lbs. Nitrogen each year afterwards.]

It is not necessary to make any comments on this table. It speaks for itself; but it does not tell half the story. For instance, in the case of wheat and barley, it gives the average result for 20 years. It shows that when 100 lbs. of nitrogen in a soluble and available form, are applied to wheat, about 68 lbs. are _left in the soil_. But you must recollect that 100 lbs. was applied again the next year, and no account is taken of the 68 lbs. left in the soil--and so on for 20 years. In other words, on plot 8, for instance, 2,460 lbs. of nitrogen have been applied, and only 775 lbs. have been recovered in the total produce of grain, straw, and chaff, and 1,685 lbs. have been left in the soil.

Mr. Lawes estimates, from several a.n.a.lyses, that his farm-yard manure contains 0.637 per cent of nitrogen, 2.76 per cent of mineral matter, and 27.24 per cent of organic matter, and 70 per cent of water.

According to this, the plot dressed with 14 tons of manure every year, for 20 years, has received 3,995 lbs. of nitrogen, of which 583 lbs.

were recovered in the produce, and 3,411 lbs. were left in the soil.

In the case of barley, 3,995 lbs. of nitrogen was applied during the 20 years to the plot dressed with farm-yard manure, of which 427 lbs. were recovered in the crop, and 3,567 lbs. left in the soil.

"I see," said the Deacon, "that barley gets less of the goodness out of farm-yard manure than wheat, but that it gets more out of the salts of ammonia and nitrate of soda. How do you account for that?"

"I suppose, because the manure for wheat was applied in the autumn, and the rains of winter and spring dissolved more of the plant-food than would be the case if the manure was applied in the spring. If the manure had been applied on the surface, instead of plowing it under, I believe the effect would have been still more in favor of the autumn-manuring."

When the nitrogen is in an available condition, spring barley can take up and utilize a larger proportion of the nitrogen than winter wheat.

Neither the wheat nor the barley can get at and take up half what is applied, and this, notwithstanding the fact that a heavy dew or a slight rain furnishes water enough on an acre to dissolve a liberal dressing of nitrate of soda or sulphate and muriate of ammonia. The truth is, the soil is very conservative. It does not, fortunately for us, yield up all its plant-food in a year.

We have seen that when wheat or barley is dressed with soluble ammonia-salts or nitrate of soda, a considerable amount of the nitrogen is left in the soil--and yet this nitrogen is of comparatively little benefit to the succeeding crops of wheat or barley, while a fresh dressing of ammonia-salts or nitrate of soda is of great benefit to the crop.

In other words, when wheat is sown after wheat, or barley after barley, we do not get half the benefit from the manure which it is theoretically capable of producing.

Now, the question is, whether by a judicious rotation of crops, we can avoid this great loss of manure?

There was a time when it was thought that the growth of turnips enriched the soil. I have heard it said, again and again, that the reason English farmers grow larger crops of wheat and barley than we do, is because they grow so many acres of turnips.

"So I have often heard," said the Deacon, "and I supposed the broad turnip leaves absorbed nitrogen from the atmosphere."

There is no evidence that leaves have any such power; while there are many facts which point in an opposite direction. The following experiments of Lawes and Gilbert seem to show that the mere growth of turnips does not enrich land for grain crops.

Turnips were grown on the same land, year after year, for ten years. The land was then plowed and sown to barley for three years. The following table gives the results:

Three Years of Barley After Ten Years of Turnips.

------------------------------------+---------------------------- Produce of Barley per Acre.

Particulars of Manures, etc. +------+------+------+------- 1853. 1854. 1855. Average 3 years ------------------------------------+------+------+------+------- bush. bush. bush. bush.

Hoos-Field-- Barley, without manure, after 3 26 35? 34? 31?

corn-crops Barn-Field-- Barley, after 10 yrs. Turnips manured as under-- 1.--Mineral manures (last 8 years) 20 19 20 20 2.--Mineral manures (8 yrs.); Ammonia-salts (6 yrs.). 23? 21 21 22 3.--Mineral manures (8 yrs.); Rape-cake (6 yrs.) 28 24? 23? 25 4.--Mineral manures (8 yrs.); Ammonia-salts and Rape-cake (6 yrs.) 29? 23 23 25?

5.--Mineral manures (8 yrs.); Ammonia-salts, for Barley, 1854 (20) 52? 26? 39 6.--Mineral manures (8 yrs.); Ammonia-salts, for Barley, '54 and '55 (20) 54? 49? 47?

The yield of barley after turnips is less than it is after grain crops, and it is evident that this is due to a lack of available nitrogen in the soil. In other words, the turnips leave _less_ available nitrogen in the soil than grain crops.

After alluding to the facts given in the foregoing table, Messrs. Lawes and Gilbert say:

"There is evidence of another kind that may be cited as showing that it was of available nitrogen that the turnips had rendered the soil so deficient for the after-growth of barley. It may be a.s.sumed that, on the average, between 25 and 30 lbs. of nitrogen would be annually removed from the Rothamsted soil by wheat or barley grown year after year without nitrogenous manure. But it is estimated that from the mineral-manured turnip-plots there were, over the 10 years, more than 50 lbs. of nitrogen per acre per annum removed. As, however, on some of the plots, small quant.i.ties of ammonia-salts or rape-cake were applied in the first two years of the ten of turnips, it is, perhaps, more to the purpose to take the average over the last 8 years of turnips only; and this would show about 45 lbs. of nitrogen removed per acre per annum. An immaterial proportion of this might be due to the small amounts of nitrogenous manures applied in the first two years. Still, it may be a.s.sumed that about 1 time as much nitrogen was removed from the land for 8, if not for 10 years, in succession, as would have been taken in an equal number of crops of wheat or barley grown without nitrogenous manure. No wonder, then, that considerably less barley has been grown in 3 years after a series of mineral-manured turnip-crops, than was obtained in another field after a less number of corn-crops.

"The results obtained in Barn-field afford a striking ill.u.s.tration of the dependence of the turnip-plant on a supply of available nitrogen within the soil, and of its comparatively great power of exhausting it.

They are also perfectly consistent with those in Hoos-field, in showing that mineral manures will not yield fair crops of barley, unless there be, within the soil, a liberal supply of available nitrogen. The results obtained under such very different conditions in the two fields are, in fact, strikingly mutually confirmatory."

CHAPTER x.x.x.

MANURES FOR OATS.

"What is the use of talking about manure for oats," said the Deacon, "if land is not rich enough to produce oats without manure, it certainly will not pay to manure them. We can use our manure on some crop that will pay better."

"That is precisely what we want to know," said I. "Very likely you are right, but have you any evidence?"

"Evidence of what?"

"Have you any facts that show, for instance, that it will pay better to use manure for wheat or barley than for oats?"

"Can't say that I have, but I think manure will pay better on wheat than on oats."

Mr. Lawes is making a series of experiments on oats. Let us take a hasty glance at the results of the first two seasons:

Experiments on Oats at Rothamsted.

----------------------------+-----------+-----------+------------ Grain, in Straw, Weight per bushels. cwts. bushel, lbs.

Manures per Acre. +-----+-----+-----+-----+-----+------ 1869 1870 1869 1870 1869 1870 ----------------------------+-----+-----+-----+-----+-----+------ 1.--No manure 36? 16? 19 9? 36 35 2.--Mixed Alkalies and Superphosphate of Lime 45 19? 24 9? 38 35?

3.--400 lbs. Ammonia-salts 56? 37 36? 17 37 34 4.--Mixed Alkalies and Superphosphate, and 400 lbs. Ammonia-salts 75 50? 54 28? 39 36 5.--550 lbs. Nitrate of Soda 62 36 42 23 38 35 6.--Mixed Alkalies, Superphosphate, and 550 lbs. Nitrate of Soda 69? 50 49? 28 38 35 ----------------------------+-----+-----+-----+-----+-----+------

It seems clear that, for oats, as for barley and wheat, what we most need in manure, is available nitrogen.

The first year, the no-manure plot produced 36? bushels of oats per acre, weighing 36 lbs. per bushel, and plot 3, with ammonia-salts alone, 56? bushels, and with nitrate of soda alone, on plot 5, 62 bushels per acre, both weighing 38 lbs. per bushel. In other words, 82 lbs. of available nitrogen in the salts of ammonia gave an increase of about 20 bushels per acre, and the same quant.i.ty of nitrogen in nitrate of soda an increase of 26 bushels per acre.

The next year, the season seems to have been a very unfavorable one for oats. The no-manure plot produced less than 17 bushels per acre; and the "ashes" and superphosphate on plot 2, give an increase of less than 3 bushels per acre. But it will be seen that on plot 3 the ammonia-salts do as much good in this unfavorable season as in the favorable one. They give an increase of over 20 bushels per acre.

"A few such facts as this," said the Deacon, "would almost persuade me that you are right in contending that it is in the unfavorable seasons, when prices are sure to be high in this country, that a good farmer stands the best chance to make money."

"Where mixed alkalies and superphosphate," said the Doctor, "are added to the ammonia, the increase _from the ammonia_ is far greater than where ammonia is used alone. In other words, by comparing plot 2 and plot 4, you will see that the ammonia gives an increase of 30 bushels per acre in 1869, and 31 bushels in 1870."

The truth of the matter probably is this: 100 lbs. of available ammonia per acre is an excessive supply, when used alone. And in fact Mr. Lawes himself only recommends about half this quant.i.ty.