Mr Cooke, in summing up the results of the interesting Norfolk experiments on barley, points out that in these experiments barley always was benefited by nitrogenous manures, sometimes by superphosphate of lime, and more rarely by potash; that of nitrogenous manures those of quickest action exerted the best influence. On an average it was found that 1 cwt. nitrate of soda per acre gave an increase of 8 bushels of barley, and 2 cwt. gave 14 bushels; while 3/4 cwt. sulphate of ammonia (i.e., the amount containing the same quantity of nitrogen as 1 cwt. nitrate of soda) gave only 5-1/2 bushels of an increase, and 1-1/2 cwt. (= 2 cwt. nitrate of soda) gave 10 bushels.
Mr Cooke recommends the following manures for the barley crop. From 1/4 to 1 cwt. of nitrate of soda, according to previous treatment of soil; from 1 to 2 cwt. super; and where it is required, from 1/2 to 1 cwt. muriate of potash.
Proportion of Grain to Straw.
Professor Hellriegel, the distinguished German investigator, has carried out most elaborate experiments on a small scale, with a view to investigating the habits of the barley plant. In the most perfectly developed of these plants, grown under the most favourable conditions, he found that the grain and straw were about equal in weight. Such a proportion of grain is, however, never realised in practice, the proportion of 2 of grain to 3 of straw being probably the common one.
Wheat occupies the first position amongst cereals, in respect of extent of cultivation, in England. As a rule it is sown in autumn, although it is also sown in spring. It is generally taken after rotation grasses or a leguminous crop, such as peas or beans, or after potatoes or roots.
Unlike barley, it does best on a clay soil, or at any rate on a firm soil, and requires a moist seed-bed. From the fact that wheat is often sown after such a crop as potatoes or a root crop to which a liberal application of manure has been given, it is not so necessary to manure it except with a top-dressing of nitrate of soda. In short, it is usually considered highly desirable to get land into "good heart" before wheat, so that the wheat may obtain its nourishment from the residue of the previous crop and the farmyard manure previously applied.
Although, therefore, as a rule, the only manure it will be found necessary to add to wheat is a nitrogenous manure, such as nitrate of soda or sulphate of ammonia, still there are circumstances in which it will be well to supplement these by phosphatic or even potassic manures. On a light soil it may be advisable to add superphosphate of lime, guano, or bone-meal, in quantities of 2 to 3 cwt. per acre, in addition to a nitrogenous manure.
Rothamsted Experiments on Wheat.
Of experiments carried out on the growth of wheat, those which have now been in progress for over half a century at Rothamsted are the most valuable and famous. In these experiments the comparative value of nitrogen and mineral manures on this crop was strikingly exemplified. The former gave a most marked increase in the crop, while with the latter little or no increase was obtained. A combination of nitrogenous and mineral manures, on the other hand, gave the most striking results. An explanation of these results may be afforded by the fact that in ordinary farming an excess of mineral matter, as compared with nitrates, is returned to the soil in the crop residues and in the straw of the farmyard manure.