with the right fertilisers

The Practical Planter

You can lift your copra yield with the right fertilisers

The use of fertilisers to produce better results in South Pacific coconut plantations was one : the subjects discussed at a technical meeting on coconut production, organised by the South acific Commission recently.

E meeting was attended by agricultural experts from all the Pacific, and was held at iroa Atoll, French Polynesia, e experts listed the coconut ing soils of the South Pacific the main nutrient deficiencies have been detected in them. ; are: Coral soils of atolls: Serious encies of nitrogen and iron; am deficiencies of manganese DOtassium.

Black, brown and red-brown loams over coral (as in New sa, the Solomons, New Hebrides Fiji): Slight deficiencies of »en and potassium.

Red to yellow clays and clay s over coral (as in New Guinea he Solomons): Serious deficiency otassium; slight deficiencies of >en and phosphorus.

Volcanic ash soils (as in New sa, the Solomons, New Hebrides Fiji): Deficiencies of nitrogen sulphur.

recise detection needed

Deep red latosolic soils (as in Guinea, Fiji, French Polynesia, Solomons, New Caledonia and Cook Islands): Deficiencies of ?en, phosphorus and potassium.

Alluvial soils (as in New ea, the Solomons and New ides): Deficiencies of nitrogen, sium and sulphur.

Coastal dune soils (as in :h Polynesia): Slight deficiency trogen. e experts pointed out, however, the deficiencies listed might not be present and that they t vary in intensity. They there recommended several methods iagnosis for the more precise tion of deficiencies and assess

ment of fertiliser requirements for particular areas.

T , ... , ..

These methods are the observation of visual symptoms, plant analysis, and soil analysis.

Nitrogen deficiency, the experts said, could be detected by pale green to yellow/orange leaves, particularly among old leaves. This condition is

accentuated by prolonged dry weather.

The symptoms for other nutrient deficiencies are * Yellowing or bronz ing of the margins and tips of leaflets followed by necrosis. Old leaves affected. • Sulphur: Leaves yellow to orange. All leaves affected. Few liv

ing fronds below horizontal posit Copra usually thin and rubbery tall varieties. • Iron: Pale green to yel leaves. All leaves affected.

On the subject of detec deficiencies and assessing fertil requirements by plant analysis, experts said: “This method is most useful diagnostic tool, but use of standardised sampling ] cedures is essential. Detailed inst: tions for sampling of leaves and waters should be obtained from analytical laboratory”.

On soil analysis, they said: “ r method can be useful but interpr tion of results is difficult”.

The experts recommended thai the correction of nutrient deficiem the type of fertiliser, rate, timing application and placement must related to local conditions, inclu< a consideration of economic fac as well as soil texture and dim “The benefit of fertilising may reduced or lost in the absence adequate drainage and maintenan they said.

General principles

As a guide, they suggested planters should follow these gen principles: • Nitrogen: On coral soils, young coconuts, annual applica of nitrates of cyanamide will be benefit. For older palms legi cover crops should be establis] On other soils alternative source! nitrogen can be used. Rates, aco ing to age, of 50-200 gm. of N palm annually are suggested. • Phosphorus: Triple su phosphate (up to 500 gm. per p depending on age) should be i annually. • Potassium: Annual applicat of muriate of potash at rates of kg. per palm will be effective. • Sulphur: Annual application 100-500 gm of sulphur, accordin] age, are the most economical m( of correction, • Iron and manganese: In yo palms 10 gm. of ferrous sulp] and 5 gm. of manganese sulp] should be applied in the husk planting and this treatment shoulc repeated after one year. When palms are two or three years 200 gm. of ferrous sulphate and gm. of manganese sulphate sh( be added to the broken husk, mature palms 400 gm. of fen sulphate and 100 gm. of mangai sulphate should be placed in a 1 at the base of the palm every tl or four years.