II July, 1910.] A/isrci^rs to Corrcsfondents. 483 



Eradication of Blackberry. — J.F.S. asks whether sulphate of iron can be 

 used for eradicating Blackberry or Eucalyptus scrub. 



Answer. — Sulphate of iron is sometimes used as a spray for weeds (60 lbs. 

 in 40 gallons of water per acre) in place of copper sulphate, being less poisonous. 

 It is, however, only of use for annual weeds like Charlock, <^:c. It injures beans, 

 peas, or potatoes, and though it retards docks and thistles, it does not destroy them. 

 The spray would be quite useless for Eucalyptus scrub and. of very little use for 

 Blackberry. Poisoning is useless for both of these. They can be killed by 

 arsenical poison, but the quantity required is so great as to render the cost pro- 

 hibitive and to spoil the ground for some years. The easiest way to eradicate 

 Blackberry is to roll it flat in summer time; burn off, taking care the fire does 

 not spread ; then knock out the charred stubbs with a mattock, rake them together, 

 pile and burn. 



Sorrel. — O.P. states that on the cleared portion of his land he has grown 

 potatoes for the past four years. After the third crop several weeds, including a 

 few patches of sorrel, appeared. This year the crop was completely smothered 

 with sorrel. 



Answer. — The condition of your land is the result of growing the same crop 

 on it for several years in succession with an exhausting manure like superphosphate. 

 Sorrel denotes exhausted land. With basic slag the exhaustion would not have been 

 so rapid. It will now be necessary to manure with lime, at least two tons per 

 acre, and to keep the soil open and well stirred until the next crop is in. A leafy 

 fodder crop would probably do best now and be most useful, but, in any case, 

 rotation of crops must be practised on small areas that cannot be fallowed. 



Plants for Identification. — D.G. (i and 2) and T.H.W. (3) forward 

 specimens of plants for identification. 



Answer. — (i) Chicory [Cichorium intybus, L.). An introduced plant which 

 may become a pest if allowed to spread. It is of some use for grazing, but 

 soon becomes hard on poor dry soils. It is not of much use for fodder, as it is 

 apt to dry black in hay, giving it a bad appearance. When growing wild the 

 roots looses its value as a surrogate for coffee. 



(2) Knapweed or Hard-heads {Centaur ea nigra, L.). An introduced plant 

 often grown in gardens and thence escaping to the adjoining lands. It is not 

 poisonous, but it takes up the place of useful vegetation and should be suppressed. 



(3) Subterranean Clover [Trifolium siibterraneum, L.). It takes 15 to 25 

 lbs. of seed to sow an acre, but is best used at the rate of 2 to 5 lbs. an acre 

 mixed with other grasses. It can be sown in autumn and spring when the ground 

 is moist and warm. Seed is difficult to obtain. 



Potato Crop. — P.P. inquires as to earliest date for planting potato crop in 

 the Longwarry district. Also desires names of most suitable varieties. 



Answer. — -Potatoes can be planted as soon as danger from frost is past; a few 

 for early crop in September or early October and the general crop in November. 

 Carman No. i, Carman No. 3 and Brownell's Beauty are recommended for the 

 early crop and Up-to-Date for the main crop. 



Peas for the Melbourne Market. — Red Gum wishes to know which varieties 

 are most suitable for the Cohuna irrigation district. 



Answer. — First crop, Sherwood ; second crop. Day's Sunrise ; ami then York- 

 shire Hero. 



Phosphoric Acid. — Subscriber writes : — " I would like to know the fertilizing 

 value of insoluble phosphoric acid compared with citrate soluble and water soluble 

 phosphoric acid. Also state whether superphosphate will evaporate or lose its 

 strength in any wav if sown on drv ground and no rain falls for three or four weeks." 



Answer. — Insoluble phosphoric acid is not available as plant food and does 

 not become so for some years. Citrate soluble is moderately soluble, and water 

 soluble is immediately available. The respective commercial values for the year 

 are : — Water soluble, 4s. 6d. per cent. ; citrate soluble, 4s. per cent. ; insoluble, 

 2s. gd. per cent. If superphosphate is allowed to remain in land for some time 

 before the available portion is taken up by the plant, some of the water soluble 

 reverts to a more insoluble form. 



Carbide. — T.S. asks whether spent carbide has any manurial value. 



Answer. — Spent carbide is similar to a crude slaked lime. Before applica- 

 tion, it is advisable to spread it over the ground and leave it exposed to the action 

 ■of the air for some time — say, a month or two — in order that any injurious sub- 

 stance present may be oxidized. It has no actual manurial value, though it improves 

 the physical condition of soil. 



