SCIENCE AND INDUSTRY. 
GREEN MANURES FOR CITRUS FRUITS. 
A summary is given in the Haperiment Station Record, vol. 42, 
24th June, 1920 (pages 830-831), of horticultural research dur- 
ing the three years ended June, 1919, carried out at “the Cali- 
fornia Experimental Station. The fertilizer experiments with 
citrus fruits begun in 1907 have been continued by H. J. Webber 
and his associates at the citrus sub-station. Uniform treatments have - 
uow been under way twelve years. The results, thus far secured, con- 
tinue to emphasize the great importance of organic matter and nitrogen, 
and the comparative slight importance, on the soils included at least, 
of phosphoric acid and potash. The plats treated with stable manure 
and raw rock phosphate, on which a leguminous winter cover crop is 
each year grown and ploughed under in early spring, continue to be 
superior to those ctherwise treated. Plats treated with chemicals, such 
as nitrate of soda alone, or in conjunction with sulphate of potash, 
superphosphate, and dried blood, have gradually deteriorated, showing 
increased quantities of mottle leaf, aud are now much inferior to plats 
that have received organic matter. In an experiment conducted to de- 
termine the best methods of rejuvenating an old citrus grove, the trees 
on two plats receiving manure and summer cover crops seemed to have - 
improved more in general appearance than the trees on any other plat, 
although other methods of treatment here noted resulted in larger yields 
of fruit. Further studies on the use of green manures in citrus groyes 
continue to emphasize the importance of this practice, bitter clover 
(Melilotus indica) and purple vetch (Vicia atropurpurea) giving the 
most satisfactory results when used as winter cover crops. Preliminary 
trials of another vetch, V. dasycarpa, have also given excellent results. 
The purple vetch is proving very desirable for use, especially on light 
sandy soils, where in some cases it has been found difficult to get a good 
stand of bitter clover. A feature that has been brought out in the 
recent experiments is the importance of using green manures in young 
groves to improve the soils while the grove is developing. In a seventy- 
acre grove planted at the citrus sub-station in the spring of 1917, black- 
-eye beans have been grown between the trees each summer, and bitter 
clover sowed broadcast over the entire area in the winter. ‘The beaus 
have more than paid for the cultivation of the grove, and the bean straw 
and clover has been returned to the land. Under this treatment the 
grove has made a remarkable growth with no other fertilizer. 
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