Table VII-The Influence of Ground Limestone on the Yield and
Nitrogen Content of Barley.

The highest average yield of dry matter was obtained with one per cent. of limestone in the soil, though a yield practically as high was obtained with ten per cent. of limestone. In pots 5 and 6 with .12 per cent. of limestone the yield is only a little higher than with no limestone. With two grams of nitrate of soda the yield is nearly as great as with one per cent. of limestone.

Percentage of Nitrogen.

The highest average percentage of nitrogen, 1.55, occurs with the nitrate of soda. In all cases except one-pots 13 and 14-the average percentage where lime was used is higher than where no lime was used. Excepting the nitrate of soda pots, the highest percentage of nitrogen occurs with two per cent. of limestone. The greatest increase in yield over the check is shown with nitrate of soda. The next greatest increase is with pots 7 and 8 where one per cent. of limestone was used. With heavier applications of limestone the increase over the check becomes gradually less though an unusually low percentage of nitrogen in pot 14 is partly responsible for this. The increase with .12 per cent. of limestone is slight.

Conclusion.

Applications of limestone ranging from one per cent. to ten per cent. gave yields of dry matter which are more than double the yield without limestone and slightly in excess of the yield with nitrate of soda. In other words the soil gave a better response with heavy applications of limestone than with a fair application of nitrate of soda. With applications of limestone the percentage of nitrogen in the dry matter was not so high as with nitrate of soda, but somewhat higher, on the average, than without limestone. It is quite clear that the presence, in the soil, of an abundant supply of limestone has enabled the plants to utilize to better advantage the nitrogen of soil organic matter. It is likewise clear that the long continued use of limestone in this way, without the addition of new supplies of organic matter in some form, would ultimately result in the depletion and

PLANTS No. PER POT.

exhaustion of the nitrogen supply of the soil. On the other hand the liberal use of stable manure or preferably the frequent growing of leguminous crops for forage or as green manure would largely supply the nitrogen, while the limestone would, as is plainly demonstrated in this experiment, aid in making it available as a plant food. The influence of lime in making available the organic matter of the soil is clearly brought out in the accompanying photograph.

FACTORS INFLUENCING THE PROTEIN CONTENT OF SOYBEANS During the summer of 1914 a number of pot experiments were conducted to determine the influence of different factors, as for example, fertilizer treatment, thickness of planting, time of harvesting, etc., on the protein content of soy beans. The crops were grown in pots holding about 20 pounds of soil or sand, and lime and minerals (phosphoric acid and potash) were added to all pots except certain ones where these materials were being tested.

THICKNESS OF PLANTING. This experiment was carried out in soil, and also in sand. In each case all pots received 4 grams acid phosphate, 2 grams potassium sulphate and 10 grams finely ground limestone. For the sand there was also added to each pot 0.5 gram magnesium sulphate and 0.25 gram ferric sulphate. All pots were inoculated with an infusion made from soil taken from a field where soy beans had previously been grown. Moisture was maintained at about 15 to 16 per cent. for the soil and about 10 per cent. for the sand. The crops were grown until the pods were fully formed, but were harvested as forage before the beans had ripened. The results from the soil and sand are shown in Table I.

Table 1-Influence of Thickness of Planting on Protein Content of Soy Beans.

823

41.7 43.83 3.450 1.439 1.503
50.4
3.372 1.699

4.5
6.0

3.321 .149

4.0

Average.

Per cent nitrogen.

Per Pot.

Average.

The rate of seeding varied from two plants per pot to twenty per pot. They were originally planted at the rate of 5, 8, 12, 16, and 25 per pot, but were later thinned to the numbers shown in the table.

In both cases the yield of dry matter increased with the increase in planting, and the increase is much more rapid with sand than with soil. The average yield for the three pots with two plants in soil is 43.85 grams and for twenty plants is 65.8 grams. The average yield for the three pots with two plants in sand is 4.83 grams and for twenty plants it is 33.67 grams.

With soil the percentage of nitrogen in all cases is above three per cent. -the average being close to three and a half-with a slight tendency to a higher percentage with the thinner plantings. With sand the plantings from eight to twenty give slightly higher percentages than those from two to five. Here the lowest yield and lowest average percentage of nitrogen is with two plants per pot.

In our earlier work we have noted quite frequently when growing barley in pots, that the dry matter from pots in which only a few plants grew contained a higher percentage of nitrogen than the dry matter from pots in which the full number of plants grew. That is, there seemed to be a tendency for the few plants to take up the nitrogen which the larger number of plants would have gotten had they been present. This does not seem to be so true of the leguminous plants and may mean that in association of numbers there is increased or intensified utilization of atmospheric nitrogen. If this be true the importance of thick seeding in the case of leguminous crops is at once apparent. It is certainly clear that

for a given area there is much more nitrogen recovered in the crop with thick than with thin seeding. Thus with soil the amount with twenty seeds to the pot is about one and one-half times the amount with two seeds per pot, and with sand the amount with twenty seeds is about eight times the amount with two seeds. The necessity for thick seeding in sandy soils seems to be especially emphasized.

Date of HARVESTING. In this experiment soil only was used, and the fertilizer and lime treatment were the same as with the soil in the previous experiments. All pots were inoculated with an infusion made from the soil taken from a field where soy beans had grown. A sufficient num. ber of pots were prepared to allow cuttings 6, 8, 10, 12, 15 and 18 weeks from date of planting. In harvesting, the stalks were cut as for forage; the soil was then removed from the pots, thoroughly washed away from the roots which were then dried and weighed separately. The variety used was the Guelph. The seeds were planted the 28th of May and the first three pots harvested July 9. The dry weight of the crop, percentage of nitrogen and other data are shown in Table II.

Table II-Protein Content of Soy Beans as affected by Date of

Referring to the dry weight of the tops, it will be noted that with but one exception (where plants were injured) there is a gradual increase from the end of the 6th week to the end of the 15th week, with a slight decrease from the 15th to the 18th, the maximum average weight being 61.93 grams. The maximum average weight for the roots occurs at the end of the 10th week, with a gradual decrease from that time to the end of the 18th week. The percentage of nitrogen in the tops reaches the average of 3.43 at the end of the 10th week and 3.42 at the end of the 15th week. The low percentage from those harvested August 20 must be attributed to the fact that while these were drying a part of the beans were eaten by rats, thus lowering the percentage of nitrogen and also affecting the weight of dry matter. With this exception the lowest average, 2.61, occurs at the end of the 6th week. A slight decrease in the percentage of nitrogen from the 15th to the 18th week may be attributed to the loss of leaves.

The percentage of nitrogen in the roots reaches a maximum at the end of ten weeks with an average of 3.17. From this date there is a gradual decrease to the end of the 18th week, when the average is 1.85. This decrease is undoubtedly due to the gradual decay and disintegration of the nodules and smaller roots, which could not be saved as the plants became older. This does not necessarily mean that nitrogen has been lost, but that it remains in the soil rather than in the roots, which were taken out of the soil.

From these results it is quite evident that if the beans are to be harvested at forage, harvesting from the end of the 10th to the 15th week will result in giving the maximum protein content. Earlier than the 10th week they have not sufficiently matured to give the maximum percentage of nitrogen, and after the 15th week the loss of the leaves may result in a lower percentage since the leaves are richer in nitrogen than the stems.

DIFFERENT FERTILIZER MATERIALS. In this experiment loam soil was used as in the two previous experiments, and all pots received 4 gms. potassium sulphate, and all were inoculated as in the previous experiments. Three pots were prepared without fertilizer, as a check, and the others received different fertilizing materials as indicated in the table which follows. On May 7th twelve Guelph soy beans were planted in each pot and later they were thinned to ten plants.

On August 14 it was noted that all plants had a good green color, and that all pods were filled, and growth had about ceased. The plants in the check pots were about 16 inches high, and all others about 19 inches high. On the 26th of August the crop was harvested, the plants dried and ground for analysis. The dry matter, percentage of nitrogen, and data with reference to the fertilizer treatment are shown in Table III.

Table III-Protein Content of Soy Beans as Affected by Different

From this table it will be noted that the yield of dry matter is quite constant. The maximum yield of 55.7 gms. occurs with 4 gms. calcium sulphate; while with 4 gms. nitrate of soda the yield is almost as high. The average yield from the check pots is 52.07 gms. which is slightly higher than on some of the pots that received fertilizer.