Foliage Feeding

Until quite recently it was believed that almost all plants were incapable of absorbing, through their leaves, any food except carbon dioxide. It has been demonstrated, however, by means of radioactive particles that inorganic chemicals can be ingested within fifteen seconds of their having been sprayed on to the foliage. All nutrients applied in this way need to be in extremely dilute solution. Urea is the compound used most commonly though salts of potassium are being added more frequently lately. It has become common practice to mix small quantities of several chemical compounds, each of which contributes one plant food element. There are several such ready-mixed powders available for foliage feeding, and they are in great demand already. Some gardeners make up their own mixtures to meet their own particular requirements. It is usual to include potassium salts in a higher proportion than is generally considered necessary in manures applied to the soil. They are relatively expensive and this may account for our not using them in larger quantities in conventional soil fertilizing. The results of foliage feeding are apparent much sooner than when the same chemicals are applied to the soil. With foliage feeding much less food is used but it costs more to apply it.

All commercial foliage feeding powders are compatible with TMTD, DDT, Lindane, E605, systematic sprays, copper oxy-chloride and wettable or colloidal sulphur preparations. When applied at the same time as any of these other materials there is, of course, no extra cost of labour involved in foliage feeding.

Some modern scientists claim that roses can be made more brilliant in colour and that reds are less likely to blue if the foliage is sprayed with solutions of various acids in extreme dilution. They claim that the leaves and stems are capable of absorbing acids from such solutions. We know that the cell-sap of the petals of vivid-red roses, such as Ena Harkness and Poinsettia has a strongly acid reaction (pH 4.6 to 4.7), that in dark-red roses such as Tassin, Mirandy, William Orr, and Chateau de Clos Vougeot the sap is less acid (pH 5.3 to <^.y) and that in pink, yellow, and white roses the reading varies from pH 5.3 to 5.96. These tests have all been done on freshly cut blooms. Experiments with acid sprays are not advised for any rose-grower who does not realize how infinitesimal must be the concentration of the solutions used; in any case, the benefits to be derived from them are small.

Soil Acidity Or Alkalinity

Soil acidity or alkalinity greatly affects the behaviour and availability of most plant nutrients. When soil is rich in available calcium, it is alkaline. The main soil acids are the colloidal particles of the clay itself. Thus heavy soils are usually more acid than sands. Carbonic acid, tannic acid, citric acid, and other organic acids are less important.

Soils will become very acid if fed regularly with flowers of sulphur , ammonium sulphate, superphosphate , potassium  sulphate, magnesium  sulphate, or organic matter in large quantities. Tan-bark is the most acid of the many organic substances commonly used. The acidity can be decreased by using lime  or dolomite . Any artificial increasing or decreasing of acidity of any plot of ground will not be permanent; it will slowly return to its original reaction.

Alkalinity reduces the availability of iron, potash, and manganese . Strong acidity reduces the availability of calcium, phosphorus , magnesium , and, to a lesser extent, nitrogen , because of an inhibiting effect on soil bacteria. The same soil will vary in degree of acidity from week to week, from level to level, and in areas separated by only a few yards. It is rarely constant anywhere.

Alkaline soil increases the incidence of crown gall  in roses. Unduly acid soils are said by some growers to predispose rose plants to black spot, but opinions are by no means unanimous on this point.

Nutrients are not absorbed by either leaves or roots as elements, but as compounds, and, in solutions, no more concentrated than one or two parts to each thousand parts of water; root hairs are killed by stronger solutions.

Chemists have done wonderful service to horticulture and agriculture in recent times. They have given us our knowledge of the constituent elements and compounds of soils, plants, animal tissues, animal excreta, and many less common things; they have found reasons for crop failures by way of soil deficiencies  and soil toxicities; they have told us what to use to remedy these defects; they have synthesized chemical (or inorganic) fertilizers  of all kinds; they have devised compounds for use as sprays  or dusts in combating disease; they have given us everything but synthetic sunlight, synthetic chlorophyll and a synthetic soil of good fertility.

Humus And Animal Manures

Fertile soil is not merely disintegrated rock holding the necessary plant nutrients in its interstices; it is vastly more than this. The fertility of soil depends on its content of humus, its drainage, and the chemical composition of the food in it. Humus has many functions; it increases the water-holding capacity of the soil, it improves the tilth and aeration, and it darkens the soil, thereby steadying temperature variation. Without humus, soil micro-organisms cannot exist. They feed on it and in so doing break it down into soluble plant foods.

The number of micro-organisms in a soil of average fertility has been estimated to reach tens of millions to the saltspoonful. They represent one of the basic factors in soil fertility and vary greatly in type. Very little bacteriological research has yet been done, but we know that some break down organic matter and that others dissolve it and assist roots in absorbing it, a symbiotic relationship. Rootlets and certain soil fungi (my-corrhizae) exist in such intimate association that there is no clear demarcation between rootlet and fungus; this is called mycorrhizal association. It is neither an accident nor a parasitic infection.

Soil fungi and bacteria are reduced to small numbers in soils that are dry or deficient in organic matter. They are killed by poisons applied to the soil (some weed-killers, some "fertilizers", and some plant sprays) or by waterlogging, which leads to lack of oxygenation and the generation of marsh gas and sulphuretted hydrogen by putrefaction.

Animal manures, as usually stored in Australia, lose most of their nitrogen by volatilization when exposed to heat and dry-ness, and by drainage when exposed to wet. Under wet conditions nearly all of the potash will drain away from any manure as well. Thereafter the value of the manure is largely mechanical, improving sandy soils by giving them body, and heavy soils by increasing their porosity and friability. It dis-appears under the disintegrating influence of soil bacteria, slowly and regularly yielding foods. Any manure rich in nitrogen is said to be "hot" or "rich"; it should be used sparingly

Cow dung is very slowly oxidized and so its effects in soil are lasting. It is particularly useful in sandy soils and in hot, dry climates. Gathered from the paddocks, it does not contain very much nitrogen, phosphorus, or potash. When fresh it is richer, and, if mixed with urine drained from the milking bails, is very strong in all three of these elements. Unfortunately we cannot often buy cow dung saved in this manner, but nevertheless it is probably the safest and best of all manures for roses. Most of it should be obtained in the winter; otherwise great crops of weeds will be imported too, for weed seeds are not killed by the cow's digestive processes. Weeds do not seed very much in winter.

Horse dung gathered from the paddocks and in a dry condition has very little manurial value other than as humus. It is very rich in plant foods if obtained from the stall, for it then contains urine and great quantities of straw. It is so "hot" at this time that it should not be put straight on to garden beds, but should be interlayered with soil in a heap and allowed to stand for a couple of weeks.

Bird-droppings are the richest of all animal manures available to the gardener. Kept from exposure, as when obtained from birds housed under intensive systems, they have a very high content of nitrogen. Nitrogen is excreted by animals principally in urine, which birds void in conjunction with their faeces; there is a relatively low potassium content. Bird manure is dangerous to plants if used too freely, because of its richness in nitrogen and because it is usually alkaline. It is improved in quality and safety if stored in a heap, mixed with earth, under cover, for a week or more. Lime is often used in bird-pens and increases the danger by adding to the alkalinity, though it liberates a great proportion of the nitrogen. Bird manure is much better without lime. The addition of dry wood ashes helps to correct the deficiency of potash.

Sheep dung contains more nitrogen, more phosphorus, and slightly more potash than either horse or cow dung. Unless collected from pens, and therefore containing a lot of urine, it is slow-acting. It usually contains great numbers of weed seeds. It should not be used from yards after the sheep have been through arsenical dips.

Pig dung is very rich, and must be used sparingly. It is best kept in a heap with soil for some weeks before use. Its moisture-retaining powers make it specially suitable for light soils, but its offensive odour makes it undesirable in suburban areas.

Blood manure is rich and quick in action. It is far more concentrated than animal excrements. It should be used almost as sparingly as chemical fertilizers, with a maximum dressing of about three ounces to the square yard. It may be applied soon after pruning and again about five weeks before roses are due to bloom in the spring or, in the summer, about two weeks before and after the summer trimming. Its lack of bulk allows of its being scattered amongst plants, with no resultant un-sightliness. Its chief active component is nitrogen.

Bone-meal contains a high percentage of phosphorus, but since it is in an insoluble form the manurial action is slow. Roses utilize the food as it is liberated by bacterial activities and the steady action of acid root excretion. Very good use may be made of bone-dust when preparing new beds. It yields only a small proportion of its plant food during the first year; the effect usually being greater during the second year; and its influence extends over many years. In subsequent years small quantities should be added regularly to the surface soil. It is so slow in acting that it is safe, even on very young plants, at any time of the year, but is easy to add in conjunction with other manures such as blood, cow dung, bird-droppings, pig dung, horse manure or compost. Containing as it does a great number of minor elements in organic form, it is one of our best plant foods.

Vegetable Manures

Straw, leaves, hay, chaff, and lawn clippings are excellent manures, increasing soil humus and providing plant foods, especially potassium, when young green matter is used, and calcium when old matter is used. They temporarily tie up some soil nitrogen while they decompose and so create a condition of nitrogen deficiency unless some nitrogenous manure is added. This correction is best made three to six weeks after the vegetable matter is spread. If applied at the same time as the vegetable matter, large quantities of nitrogen will be washed to too deep a level in the soil before it is needed, and so will be wasted and still leave a deficiency state. The nitrogen that is used in the process of decomposition of the organic substance will be released slowly as the process reaches its terminal phases, and it is at this time that plant life growing in that soil gets its greatest stimulus.

Seaweed is about equivalent to horse dung in fertilizing ingredients, but contains much more potash. The major part of the common salt present on seaweed should be hosed off it before it is spread; the small remaining quantity of salt is soon washed from it and later from the soil. Seaweed decomposes quickly and is free from weed- or grass-seeds; it is often unpleasant in odour.

Sawdust, especially that from eucalypts and pine woods, was once regarded as poisonous to garden soils, but nowadays many people advocate the use of any type of sawdust as one of best organic plant foods, and advise dressings even three inches thick. Others use it in combination with seaweed, but no matter how it is used it needs the addition of some highly nitrogenous manure to help in its disintegration. Add this some weeks later.

Wood ashes are rich in calcium and contain quantities of potash, but this latter salt quickly leaches out if exposed to rain. They are alkaline.

Some authorities consider that soot has been overrated as a fertilizer; it is almost pure carbon, none of which is of any use to plants. It contains valuable traces of minor elements, but its main value is in its nitrogen content. It appears to have some power in keeping soil free from certain types of plant diseases.

Dolomite is a natural limestock rock containing forty per cent of magnesium carbonate and sixty per cent of calcium carbonate. Where available it is a cheap and effective medium for supplying both elements. It is alkaline, but this is neutralized by mixing it with compost or other organic manure. It is especially useful in Australia's coastal districts which are deficient in magnesium.

Mallee-root dust is partly earth and partly decomposed vegetable matter. It has come from districts that are very rich in magnesium and iron, and so is a good ingredient to add to our light coastal soils, where these elements are deficient. It is very acid, and is probably best used in the compost heap.

Green crops are easy to use before planting a bed with roses, and all soils can be improved by them. In growing, they take food from the earth, but when dug in they provide even greater amounts, as well as becoming humus, and by that means, as well as by their root-growth while living, they help greatly in aeration. The commonest crops grown are legumes, Cape barley, and Algerian oats. Weeds can be regarded in the same light; they should be allowed to grow throughout the winter for reasons already stated. They can be trampled underfoot during pruning, but should be removed in early or mid August. Deep digging is inadvisable among rose plants. The weed roots should be cut no deeper than six inches, and the green matter turned in or removed to the compost heap. The crops should always be used while still young. The cheapest form of nitrogenous manure is a leguminous crop, the plants of which absorb nitrogen from the air into root nodules. In beds of established roses no attempt should be made to remove these roots, which penetrate deeply into the soil. They will be just as valuable as manures if undisturbed, but with the top of the plants severed. Temporary reduction in soil nitrogen follows the digging in of green crops, even the legumes.

Compost

World-wide experiments with inorganic plant foods, animal excreta, green crops, and compost invariably lead to the conclusion that compost is infinitely superior to the others. The object of composting is to make a humus of high plant food value. The best humus is made by composting animal and vegetable matter together. In nature the relationship between the two types is less than i to 9, and most of the vegetable matter is old and discarded by the plants. In our home composting we tend to reverse these figures. Most gardens are given nearly all animal matter, and the vegetable matter consists mostly of young matter hedge and lawn clippings, flowers, kitchen waste, and such. From a purely chemical angle humus is the perfect plant food, for it contains all the necessary plant food elements in organic form and in well-balanced proportions, and vastly improves soil texture and resistance of plants to disease, heat, and cold. There should be a large compost heap in every garden, and no pains should be spared in gathering matter for it from as widely scattered sources as possible.

The heap should be built on well-drained, bare earth, and if possible all sides should be exposed to air. No one type of matter should be placed in very thick layers, the layers should be interspersed with soil, and each few inches should be very lightly sprinkled with lime, ashes, or dolomite. The heap should be turned, by forking, after about three weeks. If it is too dry it must be lightly watered during the turning, and if too wet more soil and a small quantity of ashes should be added. It must be completely re-covered with a thin layer of soil. Excessive wetness means putrefaction with gaseous loss of food as well as leaching away of the most soluble foods, particularly nitrogen and potassium. All chemical fertilizers, disinfectants, newsprint, and coal ash should be kept out of the heap. A well-managed heap will not be offensive and will not attract flies. Compost should be spread in August and January. When growing roses for show purposes, light applications of forcing liquid manures made from blood-and-bone, animal manures with sulphate of ammonia, nitrate of soda, ammonium phosphate, and other chemicals can be added to the soil at regular intervals as the season progresses.

Liquid Manures

Liquid manures were once widely used, and have recently regained popularity. In most instances they are applied by exhibitors to force better-quality blooms. Application is useless less than twelve to fourteen days from the date on which the blooms are required. They should contain large proportions of nitrogen and should always be applied, very much diluted, to wet soil, and be followed by further watering. The most common substances used for making liquid manures are (a) cow manure, either alone or with potassium sulphate, bird-droppings, blood-and-bone manure, or soot; (b) bird-droppings alone; (c) blood-and-bone manure alone; (d) any of the former with chemicals added, or (e) inorganic fertilizers.

Liquid manures made wholly or in part from animal excreta are the best, for they contain more of the minor plant food elements. Their only disadvantages are that they become alkaline and very offensive in odour on keeping, as a result of bacterial action. These changes can be slowed by keeping the barrel cool and dark in shade and covered by a heavy sack. The alkalinity and odour can be overcome by adding acids. It should be done slowly while the liquid is kept well stirred and frequently tested lest too much be added. Litmus paper is not a very sensitive indicator of acidity or alkalinity, but it is sufficiently accurate for this purpose and is easy and simple to use. A small book of sheets costs a few pence. Blue litmus turns pink if placed in acid solutions; pink litmus turns blue if placed in alkaline solutions; blue litmus will become mauve on dipping it in slightly acid liquid manure. The best acids to use are firstly a little nitric acid followed by phosphoric acid until the manure is no longer alkaline. Both are inexpensive; neither

Contains any harmful chemical element. Nitric acid will add nitrogen and phosphoric acid will add phosphorus. Care should be exercised in handling concentrated forms of acids, for they will burn clothes or skin. Very little is needed at a time in a barrel of manure.

An adaptation of Sprengel's suction pump has been found most useful in spreading liquid manures. This consists of a piece of brass tubing with a screw adapter to attach it to the hose jet, with a second tube inserted into the brass tubing at right angles. To this side tube about six feet of plastic or thick walled rubber tubing is attached. The other end of the rubber tube is placed in a bucket of diluted liquid manure; the water is turned on and as it rushes through the main tube it slowly sucks liquid from the bucket, greatly diluting it as it spreads it on the garden. If a fairly weak solution is placed in the bucket, one need never fear that any damage will be done even by hosing over the young foliage and buds. The jet may be used at the same time for washing off aphis and dust. This method will obviate the back-breaking task of carrying heavy cans of water, will save a great amount of time, and can be done frequently and safely. The device is very simple, and can be made at small cost by any plumber.

Mixed manures can be used, spread direct on the soil. The best of these combinations are (a) cow dung with blood-and-bone manure; (b) cow dung with bird-droppings; (c) cow dung with horse dung collected from stalls; (d) bird-droppings with ashes and bone-meal. Dolomite can be added, with advantage, to any of these mixtures or to compost if the soil is too acid.

Manures may be applied in small quantities at almost any time, but with greatest advantage just after winter pruning and about two weeks before summer trimming, when good heavy dressings should be given. Probably more is needed in the summer application than in winter, for roses will give excellent spring blooms even if left wholly unfed. Very little permanent benefit results from subsoiling or trenching unless organic matter is added to improve the physical soil texture. In early summer a mulch of organic matter is useful. It should not be highly nitrogenous lest it force very soft growth. It keeps the soil at a steady temperature, helps to conserve moisture, and facilitates the absorption of rain, or water artificially applied all of which factors help roses to grow steadily and resist disease.

The idea has been instilled into the minds of many rose-growers that immediately a plant shows signs of weakness the first necessity is heavy feeding, and a dressing of blood-and-bone or sulphate of ammonia is duly given. Only strong healthy plants can take such food even in moderate quantities. In no circumstances must a weak or sickly plant be given manure of any kind. The drainage should be tested, and if found efficient, heavy waterings are the best treatment for the plant.

It should always be remembered that manuring is only one phase, albeit a very important one, but healthy soil conditions, adequate drainage, and the maintenance of optimum soil moisture form the foundation of success. Few roses are killed by inadequate manuring.

Parts of this chapter are rather technical and will interest some readers merely for reference purposes. Not all manures discussed will be available; for instance, the country gardener will rarely have seaweed, the city gardener finds animal manures increasingly difficult to obtain, and dolomite is much better known, more easily obtained and more widely used in Sydney than in Melbourne. If a gardener can grow good annuals, vegetables, and shrubs he can grow good roses.

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