Fertilizers

The life of plants comprises the processes of nutrition, breathing, growth, generation and responses to environment. All these processes of the live organism involve consumption of energy and of the matter which is to constitute the texture of the organism.

The chemical elements constituting the organism are numerous, and they are either assimilated from the soil or - if the soil is poor or exhausted - they are provided artificially by means of applying various fertilizers, or else by liming and the use of gypsum.

The fertilizers used in modern agriculture may be subdivided into organic and mineral. Organic fertilizers comprise: barnyard manure, peat, green manure (from certain plants assimilating nitrogen from the air) and various composts. Composts contain not only organic, but also mineral matter. Inorganic fertilizers comprise various ingredients, but the most important elements are nitrogen, potassium and phosphorus. The primary for obtaining nitrogenous or nitric fertilizers is ammonia. Ammonia is obtained synthetically from nitrogen and oxygen or as a by-product of coking. Most widely spread are ammonium sulphate, nitrates such as urea, and liquid ammonia. Ammoniacal fertilizers are water-soluble and are well assimilated by plants, but they act more slowly than nitrates.

The initial raw material out of which phosphate fertilizers are obtained are apatites (of which there are numerous deposits in the Russia) and phosphate rock. The following kinds of phosphate fertilizers are known: superphosphate, pelletized and double, defluorized phosphate and ammophos. Phosphorites are finely ground as a result of which phosphate meal is obtained. Especially valuable is pelletized superphosphate. It is well applied with ferti-seeding, contributing greatly to germination.

Potassium-containing or potassic fertilizers are obtained from potassium rock salts, also widely occurring in the Russia. Potassium chloride, potassium sulphate, kainite are the chief commercial fertilizers derived from these salts.

But the three main elements are far from everything needed to thrive well. Plants need a number of other elements, notably: carbon, oxygen, hydrogfen, sulphur, calcium, so­dium, boron, molybdenum, manganese, copper and even iron. Fertilizers containing such elements are called minor nutrients or trace fertilizers.

All kinds of fertilizers are assimilated through the root system of plants. Liming (the application of lime) is often also necessary on acid soils.

Not only must these elements be introduced into the soil, the proportion of each should be strictly calculated, and often it is best to combine several elements in one fertilizer. In this connection concentrated compound fertilizers are of high value. These not only provide all the necessary ingredients in the right proportion, but also permit of a considerable saving in bulk and weight. Thus if we use ammonium sulphate, ordinary superphosphate and sylvinite, then in order to introduce 60 kg of nitrogen, 60 kg of phosphorus and 60 kg of potassium, a ton of these fertilizers is required; at thesame time if synthetic urea, double superphosphate and potassium chloride are applied, the same amount of nutritive ingredients will be contained in 370 kg of the mixture. The compound fertilizers based on ammonium nitrate, ammonium phosphate and ammonium sulphate have great advantages. The fertilizers are a free-flowing granular product and provide considerable sayings in handling costs resulting from the higher concentration of these products cottipared with traditional superphosphate based compounds. Today there is a demand for even higher concentrations and new manufacturing processes have been developed to provide a wide range of compound fertilizers based on ammonium nitrate in place of ammonium sulphate, and containing nitrogen, phosphates and potash in any of the usually required formulations.

These formulations have the following important advantages: 1) High concentrations: giving economies in handling, bagging, transport and spreading costs. 2) Exceptionally good storage properties. The products consist of well-shaped granules substantially in the size range of 1.5-3.5 mm, completely free from dust. 3) They are suitable for all crops and all types of soil. 4) The products are so formulated as to avoid the self-sustained decomposition which has characterised some types of nitrate-based complex fertilizers. 5) The products do not show the adverse effects on germination nor the nitrogen losses which have been occasionally observed in the highest concentration products from other processes.

In certain areas, particularly tropical regions with high rainfall and acid soils, the need for highly water-soluble phosphate is not important. For such regions we can use ground phosphate rock.

But how do agriculturists know about the effect of various fertilizers? Tracer atoms come to their help. Isotopic tracers are among the most important tools of the biochemist and agriculturist, and fundamental advances of agricultural knowledge have been made with their aid.

Isotopes are now indispensable in biochemical research; primarily in establishing the basic chemical reactions which occur in normal living things.

Agriculture benefits from knowledge gained by tracer methods not only in the application and assimilation of fertilizers, but also through the control of insecticides in plants and insects.

At present in most cases fertilizers are introduced into the natural soil, but a new system of growing plants and fertilization is today also making headway. It is known as hydroponics. A bed of gravel or sand is made on a rack arid all the necessary fertilizers without exception are added. Of course, the necessary moisture content is provided. Plants thrive wonderfully on such a bed. But a further improved system has been devised. A film of synthetic rubber, able to follow the natural lay of the ground is put on the soil, whereupon sand or gravel together with the necessary fertilizers are placed. The film prevents the appearance of weed grasses and moreover impedes the formation of dunes, likely to arise as a result of wind erosion. These films are especially suitable for growing vegetables.

Сrops

By the word crop we understand every useful plant cultivated for the benefit of mankind.

Depending upon their field of application, crops can be subdivided into the following groups:

1) Food crops, comprising mainly cereals, or grain crops:

Under this head comes first and foremost wheat grown practically at all latitudes and constituting the essential primary for milling, baking bread, etc. Wheat is followed by rye grown essentially in Northern countries. Rye yields brown bread.

Next to rye in significance comes barley used for the preparation of gruels and for malting. As is well known, malt is what beer is made of. Buck wheat and millet serve principality for making gruels. It would perhaps be difficult to say whether oats belong to the group of feed crops or food crops. Porridge is made of it which is a highly nutritive food for humans, but oats are particularly widely employed for feeding domestic animals. Oats are an excellent feed for horses, milch cows, growing calves and laying hens on account of their high protein content. Oats also have a stimulating effect upon horses. Thus from the point of view of the food industry, it is a food crop, and, considered from the angle of cattle-breeding, a typical feed or kind of fodder. The same can be said of maize (corn in the USA) which is a food-stuff and a means of fattening cattle (principally hogs).

Rice. Its cultivation requires an immense quantity of moisture. It grows best in fields which can be flooded. Such rice is called lowland rice while rice grown without inundation bears the name of upland rice. Rice when not yet husked is called paddy.

Special mention should be made of crops used in the production of beverages.

Tea. The tea plant grows in China, Japan, India and the South of the Russia. It is a hardy evergreen, from three to six feet in height. The leaf is the part of the plant of which tea is made. The difference in the quality of tea is due partly to the district in which it is grown, partly to the time at which it is gathered. There are four harvests in the year - in April, May, June and August. The first gathering is confined to the choicest leaves only, andis the finest; the last gathering is the lowest quality.

Coffee. The coffee-plant grows in North Africa, the East and the West Indies, and Brazil. The seeds of the fruit, which is about the size of a small cherry, are the parts of the plant which yield coffee, and are called coffee-beans. Coffeeowesits stimulating properties to an element called caffeine, which is identical with the active principle in tea and cocoa.

Cocoa. This is the seed of the cocoa tree, which grows in the West Indies and in several parts of South America. The seed is contained in pods about five inches long, and is somewhat like a cucumber. Chocolate is simply the ground cocoa-seeds made into a paste with sugar and flavoured in various ways, but chiefly with vanilla.

Grapes grow on bushes in vineyards principally in the South. The plant itself is known as vine. The art of growing grapes is known as viticulture. Grapes are much used for making wine.

2) Feed crops are those, the main purpose of which is to supply provender to cattle. Many varieties of grasses can be listed under this head. Clover takes the first place, but timothy, alfalfa and vetch all find their useful application; many of these grasses serve at the same time the purpose of returning to the soil those particular nutritive elements which the preceding crop has extracted from the earth.

Grass-sowing is, in fact, not a minor factor in planning crop rotation. Swedes are also an important feed crop, along with mangle.

3) Industrial crops are those that provide raw materials for further processing. Sugar-beet is the main primary for the sugar industry, while various fibrous plants such as flax and hemp yield respectively linen and rough cloth, along with sacking.

Flax. The flax plant yields the fine fibres of which linen is made. It is an annual plant bearing blue flowers. It is now cultivated in nearly every country in Europe, as well as in Egypt and India. The stems, after being dried, are soaked in dew or in water, to destroy their green outer bark. The interior fibres are then dried and scutched to separate the threads completely. They are then hackled, or combed out, when they are ready to be spun, or twisted into yarn. The finer kinds of flax are made by repeated hackling.

Hemp. The hemp plant was originally a native of Persia and Northern India, but it is now extensively cultivated in the Russia, as well as in North America and Africa. The part of the plant which yields the fibres for manufacturing is the stem which is treated in much the same way as that of the flax plant.

Cotton. Perhaps the most important industrial crop for the textile industry is cotton. The cotton plant, three or four feet in height yields the cotton fibre. The commercial value of cotton depends on the length, the staple and strength of the fibre. In preparing cotton, the seeds, enclosed in bolls of down, are separated by an apparatus called a gin. The cotton is then compressed into bales and sent to a factory for making cotton fabrics. The seeds are either kept for sowing again, or are used in making oil and oil-cake for cattle. Cotton generally grows on bottom or irrigated lands.

The sunflower plant yields the best oil - sunflower oil; cotton and even flax oil are both edible, though falling of course short of the pleasant taste and flavour of olive oil, cocoa-nut oil and some other oils which rank first among salad and other seasoning preparations.

With the development of synthetic rubber, rubber-bearing trees, though partly holding their own, have to a great extent given up their former industrial significance. And although chemical technology has provided the world with new esters, essential oil bearing plants are still being grown, finding themselves a particularly vast range of application in the perfumery industry.

4) The fourth group is represented by vegetables. Though these are mostly to be seen in vegetable gardens, yet we can observe vegetables growing on vast areas of field land. The system of growing vegetables on a large scale is termed truck-farming.

Vegetables can be subdivided into the following groups: root crops comprising beetroot, carrots, turnips, radish, etc., fruit crops embracing tomatoes, water melons, musk melons, and pumpkins, as well as cucumbers; cole crops, to which cabbage belongs in first place; pulses covering peas, beans, lentils, etc. Last not least come tuber crops, principally potatoes.

Potatoes, comparatively recently introduced into Europe (they were brought from America) not only constitute an important foodstuff, but are also used for the manufacture of starch. Cauliflower, onions and swedes (used principally as a feed) also rank high in truck-farming.

Every year, new varieties of crops, cold-resistant (not subject to winter-killing), more nutritive and more tasteful are being evolved on experimental test plots.