BOIL FERTILITY.

Dominion, Volume 6, Issue 1652, 20 January 1913, Page 10

BOIL FERTILITY.

AN AGRICULTURAL EXPERT'S • VIEWS.

"Soma Physical and Chemical Factors. Affecting Soil Fertility and the Growth of Crop/' was tho subject of a paper by Mr. It. J. CJolbourn, Agricultural Jixperc ' and Chemist to tho Government of Tasmania, at the recent science congress in Melbourne. Ho said that it was well known to the scientific agriculturist that the germination of tho seed of any plant was dependent upon three principal factors, viz., an adequate supply of dxygen, moisture, and warmth. It was' obvious to auyone who had had experience of soils that ono which-had once been- brought into good cultivation' was for'a long time to come much easier, and, in consequence, less expensive, to work than one in' a contrary condition. Hence tho, first outlay incurred might, with proper manage* inent, be spread over a considerable period, • Again, the presenoe. of an. abundant-supply of humu9 or decayed, vegetable matter, in/ a soil exerted a very favourable ciFect - upon' its texture, stillfurther. rendering it less costly to■ manipulate. This wa3 a strong argument in lavour of occasionally ploughing -in a green crop, which,'upon decay furnished much available* plant. food. Moreover, ■the . production,\ of carbonic 'acid which wont on.during the process of decomposi-, tion, exerted a. valuable indirect effect in liberating much mineral plant food from the reserve supplies'of. the soil. - The -groen. crop should,,of .course, beleguminous if possible,-on ac&ount of the well-known property possessed by this otder of plants pf- gathenng nitrogen from tho atmosphere, thus-greatly enriching the soil with; a'very Valuable plant' lood. A' praci tical point' worth noting in connection, • with green-manuring was the liability of : the soil to 'be- too hollow for the crop 'that might be sown immediately afterI'- This condition: commonly occhrred if dry weather/sets in shortly after tho-green crop was ploughed in, the result being the formation of air cavities in th'e[ soil;, This condition was to bo improved, or,. perhaps, remedied altogether by means of roller,* disc harrow, or other suitable; implement which might be to iha'nd. ' The. green crop'during the early stages of its,, decomposition, in the soil sometimes developed an injurious degree of sourness, which might, however, be\ mitigated by applying a good 'dressing of' lime to-the land at the" time the plough-' ing-in took place.. This not only tenued to correct sourness, but further promoted tho decomposition of .the'.-mass of vegetable matter/which had been ploughed lri.' 'Another important factor which foncernI ed the amelioration of the texture of the sbils' was lime. '-. This valuable substance acted both chemically and physically, upon tho soil.' Chemically, it promoted nitrification or the conversion of tho , crude nitrogen of the soil into nitrate of lime, one of the best of fertilisers; it 1 liberated; potash from ' its combinations, ahd rendered it available for plant food. •To sumtharise liming* abundant tillage.'.and the maintenance of a gdod supply of.humus in the soil wero , the chief. factors in successful farming, so far 89 the production of crops was .'concerned.';':'' Under these conditions a minimum, of fertilisers would be required, as so much of< the natural resources of. the soil .would'be. rendered available: and, further, drought, would have far less effect, and crops be brought to maturity much, earlier, besides other advantages which .'must occur to every practical man.