RURAL NEW-YORKER says: "It is much to be regretted that certain writers are advocating the use of nitrate of soda. Unless the land is well supplied with potash and phosphoric acid and needs nitrogen alone, nitrogen will not materially increase the crop." This is a self-evident proposition. And the same thing might be said of soda, lime, magnesia, sulphuric acid and iron. All these ingredients of plants are absolutely essential to healthy plant growth.

There are people who contend that to maintain the productiveness of our land it is necessary to return to the soil the amount of plant food that the crops remove. They overlook the fact that a certain amount of plant food is rendered available each year from the store of plant food lying dormant in the soil. If this is sufficient we need use no manure. If any one element is deficient, we must supply the deficiency or be satisfied with a deficient yield. The weakest link in a chain determines the strength of the whole chain. If we find out the weakest link and strengthen it, then some other link would be the weakest. As a rule, for most garden crops, our soils are deficient, 1st, in nitrogen; and when this is supplied, they are deficient, 2nd, in phosphoric acid; and when this is supplied, they are deficient, 3rd, in potash, and so on through every link in the chain.

For forty years or more, efforts have been made to find out what ingredients of plant food are most likely to be deficient. It was proposed to analyze the soils. This was found to be practically useless. The idea was then advanced that the amount of plant food in the crops would tell us the amount necessary to apply in manure. Lawes and Gilbert's experiments, over forty years ago, demonstrated the fallacy of this idea, but every now and then it shoots up again and grows as vigorously and perniciously as ever.

As we said last month, what we need, especially for garden crops, is not "soil tests," but experi-ments that will show what plants require a " sap of the soil" specially rich in nitrogen or in phosphoric acid or potash. In other words, we want to ascertain the weakest link in the supply of food for different plants; and there is no way of getting at the facts except by actual experiments.

When the editor of the Rural says it is much to be regretted that we are advocating the use of nitrate of soda, he overlooks the fact that we advocate the use of superphosphate with equal earnestness, and, in some cases, of potash also. The object of these articles was to show that when gardeners use the ordinary commercial fertilizers, they spend a great deal of money for plant food that their crops do not need. For instance, if they want to apply 100 pounds of nitrogen on an acre of land, and 50 pounds of phosphoric acid, and buy a fertilizer guaranteed to contain 2 per cent, of nitrogen and 12 per cent, of phosphoric acid, they will have to sow 5000 pounds to the acre, and this will furnish twelve times as much phosphoric acid as is required. What we contend for is that they should buy the necessary phosphoric acid in the cheapest and best form and be sure to use enough of it, but not too much. To put on twelve times as much soluble phosphoric acid as is needed, in order to get the necessary nitrogen, is folly. If you want nitrogen as well as phosphoric acid, buy the nitrogen in the cheapest and best form.

If we recommend nitrate of soda to those who wish to buy nitrogen, it is because the nitrogen is in the best and most available form, and because, at the present time, it is the cheapest source of nitrogen.

There are enormous beds of it in South America, and its use in Europe is rapidly increasing, while with us, it is almost unknown. It certainly is well worth our while to see if, especially in our dry and sunny climate, we cannot use it to great advantage.

The editor of the Rural New- Yorker further says : "In experiments made at the Rural grounds during two seasons, to ascertain the effects of nitrogen on potatoes, it was found that additional quantities of nitrate of soda or sulphate of ammonia or blood, or all three, beyond what was supplied by the 'complete' fertilizer, did not increase the yield in any case. * * * From 1,200 to 2,000 pounds of the fertilizer was used, guaranteed to contain 3½ per cent, of nitrogen, 12 per cent. of phosphoric acid and 6 per cent. of potash. It appears, therefore, that the amount of nitrogen supplied by the fertilizer was amply sufficient for the crop's needs, and that the added nitrogen was so much money thrown away".

Mr. Carman, the able editor of the Rural New-Yorker, made better experiments than his allusion to them above would indicate. Our own personal objection to them is that they were on too small a scale to carry conviction to an old farmer and gardener. The plots were only 1/440 part of an acre each. One good feature, however, was that four plots were left without manure. These plots produced at the rate of 88, 97, 68 and 59 bushels per acre each. The variation in the land, therefore, was 38 bushels per acre. Bearing this fact in mind, let us look at some of the more important results bearing on the subject we are discussing.

There is certainly nothing in these results contradictory to the principles we have advocated in The American Garden. Mr. Carman states that the soil had been cropped for many years without manure of any kind, and that it "would not grow beans, or even a good crop of weeds without manure." And yet it will be seen that nitrogen alone, on plot 5, produced 183 bushels of potatoes per acre, while on plot 8, 1,020 pounds of a "complete manure" produced only 156 bushels, or 27 bushels less than nitrogen alone. Why is this ? Did the phosphoric acid and potash do harm ? No ; there was not nitrogen enough. The phosphoric acid and potash could not increase the crop for lack of nitrogen.

Mr. Carman tells us that he used from 1200 to 2,000 pounds of a complete fertilizer, guaranteed to contain 3½ per cent. of nitrogen, 12 per cent. phosphoric acid and 6 per cent of potash, and that when he added more nitrogen, it did no good. Why should it ? Oats are good for horses, but when a horse has all the oats he will eat, throwing more oats into the manger will not increase his strength or improve his appearance. If the ton of complete fertilizer furnished all the nitrogen the plants wanted, more could do no good. But for the sake of getting 70 pounds of nitrogen, what folly it is to use a ton of fertilizer that contains a great deal more phosphoric acid, costing 8 cents per lb., than the crop can possibly want ? This is the point we wish to impress on our readers. And it is a matter of surprise that so clear-headed and able a man as Mr. Carman does not see that his own experiments demonstrate, if they demonstrate anything, that, so far as the production of potatoes is concerned, this worn out soil, that was so poor that it would not grow a good crop of weeds, was more deficient in available nitrogen than in any other constituent of plant-food. Superphosphate and potash, without nitrogen, did no good. They could produce no effect from lack of nitrogen.

Thirty-two pounds of nitrogen per acre, in the form of nitrate of soda, raised the crop from 74 bushels per acre (or possibly 59 bushels) to 141 bushels per acre. The same amount of nitrogen on plot 8, in 1,020 lbs of "complete manure" produced 156 bushels, the 820 lbs. of superphosphate and potash only increasing the yield 15 bushels per acre, - not as much as the difference in yield of the un-manured plots. Nitrogen alone, on plot 5, produced 183 bushels per acre. It is clear, therefore, that a complete manure, like that used on plot 8, containing about 3¼ per cent, of nitrogen is a very costly and "badly balanced ration" for potatoes. It does not, for Mr. Carman's poor, worn out soil, contain half nitrogen enough. It is true that by using enough of it you could grow a large crop, but it would be done at a fearful and unnecessary expense. We feel perfectly safe in saying that a ton of it per acre would produce no larger a crop than half a ton that contained double the amount of nitrogen.

A complete manure, such as that used on plot 8, would probably cost $40 per ton. The 200 lbs. of nitrate of soda in the mixture can be bought for $5. In other words, the phosphoric acid and potash in the ton of this complete manure cost $35. Leave half of it out and double the nitrate and you will, in our judgement, get quite as large a crop at far less cost. There is nothing in Mr. Carman's experiments, or any other, to lead us to suppose otherwise.

Moreton Farm. Joseph Harris.