Scientific Agriculture. 



554 



[June 1908: 



McKeown calculates that he succeeded 

 in obtaining 95 per cent, of the total 

 weight of root in the soil. The produce 

 of tops from one square yard was 4 lb. 

 14§oz., or 10 tons 12 cwt. per acre; and 

 of roots, 11 lb. 9 oz. per square yard, or 3 

 tons 7 cwt per acre. Analysis showed 

 that the tops contained 87 per cent, 

 water (13 per cent, dry matter), and 506 

 per cent, nitrogen ; the roots contained 

 83 per cent, water (17 per cent, dry 

 matter), and 213 per cent- nitrogen. 



When, therefore, this crop is ploughed 

 under, it will add to each acre of the 

 soil, in the shape of dry matter, 1 ton 7 

 cwt. tops, and 11| cwt. roots, including 

 120 lb. nitrogen from the tops and 16 lb. 

 nittogen from the roots ; a total of 1361b. 

 nitrogen per acre. Assuming that condi- 

 tions are favourable for nitrification, 

 this will be equivalent to a dressing of 

 nearly 7 cwt. sulphate of ammonia per 1 

 acre, or over 11 cwt. dried blood — in 

 enormous dressing. 



The soil in which this crop was grown 

 was a light loam with about 25 per cent, 

 clay. The clay is of a tenacious char- 

 acter, and has a tendency to cake hard 

 on drying. The soil is low in humus, con- 

 taining only about 4 per cent of this 

 ingredient. It is fairly rich in potash 

 and satisfactorily supplied with lime, 

 but rather low in nitrogen and phos- 

 phates. It is consequently .just the type 

 of soil in which green-manuring should 

 be effective, as the effect of ploughing 

 under the crop will be to break it up and 

 render it more friable, and to supply the 

 deficiencies in humus and niti'ogen. Its 

 efficacy is, of course, dependent upon 

 conditions as to rainfall being favour- 

 able to its decomposition in the soil. 

 The climate of Wagga is not very 

 favourable to the growth of these crops. 



At Bathurst, and at the Hawkesbury 

 College, where conditions are more 

 favourable the benefits of green-manur- 

 ing are even more striking. Mr. Allen 

 obtained samples of tops and roots, 

 representing the produce of one square 

 yard from crops grown at these places, 

 and they gave the following figures :— 



At Bathurst, the tops weighed 17 lb. 

 and the roots 2 lb. 5 oz. per square yard, 

 or 36 tons 14 cwt. tops and 5 tons of roots 

 per acre, giving a total of dry matter to 

 be ploughed under of 4 tons 15 cwt. from 

 the tops and 16 cwt. from the roots. 

 Assuming the same nitrogen content in 

 tops and roots as was found in the 

 Wagga plants, this will give when 

 ploughed under 411 lb. nitrogen per acre 

 from the tops and 22 lb. nitrogen from 

 the roots. 



At Hawkesbury, the produce was 21 

 tons 12 cwt. tops and 4 tons 14 cwt. roots 

 per acre. When ploughed under, this 

 would yield 2 tens 16 cwt. dry matter 

 from the tops and 16 cwt. dry matter 

 from the roots. With *5 per cent, nitro- 

 gen in the tops and *2 per cent in the 

 roots, the soil will be enriched in nitro- 

 gen by 212 lb. per acre from the tops 

 and 221b. from the roots. — Agricultural 

 Gazette of New South Wales, March, 1908. 

 Vol. XIX, Part 3. 



THE SOURCES AND USE OP 

 NITROGENOUS MANURES. 



(Abstract of " Die Stickstoffquellen und 

 die Stickstoffdungung," by W. Schneide- 

 wind.) 



Of the various constituents of com- 

 mercial fertilizers nitrogen is undoubted- 

 ly the most expensive. Not a little skill 

 and intelligence are required on the part 

 of the farmer, for placing before the 

 growing crops a proper supply of nitrogen 

 food in a manner both economical and 

 efficient. The growing cost of nitrate of 

 soda, the increasing production of sul- 

 phate of ammonia, the more or less 

 successful attempts to manufacture 

 nitrogenous materials out of the nitrogen 

 gas in the air, and finally the various 

 systems of green manuring and tillage 

 are factors to be reckoned witb. The 

 situation is thus decidedly confusing, 

 even to the progressive farmer, and it is 

 not always easy for him to determine 

 the best methods to be pursued. 



Apart from the nitrogen removed in 

 crops, gains and losses of this constituent 

 constantly occur in the soil. Quantities 

 of nitrogen compounds are brought to 

 the soil in the rain, dew and snow; 

 further additions occur through the 

 absorption of ammonia from the air by 

 the soil humus, and through the building 

 of such compounds by bacteria living 

 directly in the soil or in the root nodules 

 of leguminous plants. On the other 

 hand, the store of nitrogen in the soil 

 may be diminished in various ways. The 

 decay of the soil humus, which is caused 

 by bacteria, involves the breaking down 

 of nitrogenous compounds and the setting 

 free of some of their nitrogen. More- 

 over, a portion of the nitrogen may be 

 lost by the formation of ammonia and 

 its partial escape into the air, Pully as 

 important as these two is the leaching 

 out of the soil of very considerable 

 quantities of nitrates, themselves derived 

 from the decay of humus, of manure 

 and of animal or vegetable substances in 

 commercial fertilizers. 



