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Observations of soil populations of Ditylenchus dipsaci (Kühn) Filipjev were made in the north of England from 1963 to 1969. Samples were taken in spring and autumn or winter from the same 14 commercial fields where oat cultivars susceptible to D. dipsaci had been damaged previously by this pest, from field plots under different rotations and different weed control programmes and from microplots under different crop rotations. In fields and field plots growing cereals, populations generally increased during summer and decreased during winter. Large increases occurred when oats were grown. With swedes, potatoes and ley, slight reductions occurred during summer and larger reductions during winter. Seven of the 14 sites contained populations below detectable levels after 2-8 years without an oat crop; in the remainder, detectable numbers were still present 1-7 years after an oat crop. Field plots receiving no herbicide maintained larger soil populations of D. dipsaci. Approximately 40-60 per cent of oat plants were damaged in crops grown after one or two years' barley and about 20 per cent after three years' barley whether or not herbicides had been applied. In microplots kept weed free, three years of barley, grass, or barley) grass rotation, three or four years' fallow or three or four years' weeds reduced soil levels of D. dipsaci by 99-100 per cent. After all these rotations one oat crop increased the soil population to detectable levels and a second oat crop showed symptoms of damage. [ABSTRACT FROM AUTHOR]

Presents studies in the nitrate nutrition of two indigenous Rhodesian grasses. Significance of soil fertility in secondary succession of plants; Implications of the relationship between nitrogen fertility and secondary succession; Analysis of three methods to find the most appropriate assay procedure.

Infrared imagery in the 4.5 to 5.5 micron wavelength band was obtained in July, 1965. Interpretation and subsequent field checking indicated that differences in agricultural land use can produce tone differences in infrared imagery and that these differences tend to be more pronounced in day than in night imagery. Differences in soil fertility and cultivation practices were observed that created significant differences in tone of a single crop. The value of first-hand field information in the area being interpreted was clearly demonstrated. Interpretation accuracies of ninety percent for separation of cultivated and noncultivated lands, ninety-five percent for recognition of alfalfa, seventy percent for corn, sixty-five percent for soybeans, and eighty-five percent for separation of wooded and non-wooded areas of noncultivated lands were achieved. Interpretation of tree species and separation of pasture and brush lands were not achieved with an accuracy of over fifty-percent. [ABSTRACT FROM AUTHOR]

Colonization of wheat roots by Gaeumannomyces graminis (syn. Ophiobolus graminis), the take-all fungus, was slower in inverted grass turves or soils from beneath grass crops than in fallow soil. Control of the growth of G. graminis in turves was completely lost when they were sterilized and recolonized by micro-organisms from fallow soil, and was therefore due to micro-organisms present on the grass roots. Most, if not all, of this control is ascribed to Phialophora radicicola, because the effectiveness of different turves was directly proportional to their populations of P. radicicola; fallow soil inoculated with a natural population-level of this fungus restricted colonization of wheat roots by G. graminis. The high populations of P. radicicola in all English grasslands examined, its rapid build-up to these levels and the considerable carry-over on successive wheat crops after grass (Deacon, 1972) suggests a role for short-term grass leys in the control of take-all in intensive cereal rotations. But, grasses can partially maintain the population of G. graminis between cereal crops, and so they should not be sown immediately after a heavily-infected crop. [ABSTRACT FROM AUTHOR]

A number of geographic factors, principally climate, topography and soil fertility, operating either separately or in varied combinations influence agricultural conditions. Of these, climate is the most fundamental, unalterable and important, not only in influencing the distribution of particular crops, but also in determining the suitability of land for agricultural purpose. The land surface of the earth may be classified broadly as potentially agricultural and non-agricultural. In the Great Plains it is the rainfall of the crop growing season with which the farmer is mostly concerned.

This paper discusses the existence of an open-field type of cultivation in Mediterranean lands and in the Atlantic Coastal lands of south west Europe. In certain islands of Brittany, France traces of an open-field type of cultivation still exist. Exposure to the westerly winds retards, and in many cases entirely prevents, the growth of trees, but in sheltered spots they may be found, as well as such sun-loving plants as mimosa, myrtle and vine. The islanders are occupied with fishing and farming. In the Balearic Islands also, the Minorcans are fishermen, while the Mallorcans have been enterprising navigators from earliest times. In all these islands the sillon is the basis of land tenure, and many sillons are cultivated in common. Communal methods of working were also characteristic of other occupations in the islands. The fertility of the soil is maintained by the application of manure in the form of seaweed, and there are very strict regulations concerning the cutting of this plant. In Ile d' Arz, France, with a two-field scheme, the ancient jachère morte has been replaced by the Jachère verte or green fallow. Barley and wheat, both varying in their species as much as the soil varied in its composition, were the cereals most usually grown. The mountains in Greece have limited the extent of the fertile land, and the dry climate has limited its green pastures.

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This article discusses the movement trends among farm population in Oklahoma. During the period from 1930 to 1935 there has been an exodus of farm population from southwestern counties. The explanation for this movement is the excessive drought of 1934 preceded by two years of below-average rainfall that greatly reduced cotton production. Second, farm labor has been displaced by the growing use of mechanized farming methods. It may be concluded from the foregoing discussion that factors contributing principally to the mobility of population in Oklahoma are as follows: due to the relative newness of the state, sufficient time has not elapsed for the population to become fully absorbed into the existing economic patterns; the depletion of such natural resources as soil fertility and petroleum; the surplus population has tended to migrate into areas in which self-sufficing agriculture alone cannot afford more than the necessities of meager existence; instability of population in western Oklahoma counties; and labor displacement and the decline of out-of-state markets for non-agricultural products.

The importance of mineral nutrients for the growth and distribution of bog vegetation has been much discussed in Sweden in recent years. The distribution of many mire plants is correlated to certain chemical characteristics of the water or substrate, and marked changes in vegetation have occurred after addition of mineral fertilizers. Yet the causal connections between environmental factors and plant occurrence are little known. This article presents findings of an experiment describing the nutrient turn-over in a bog community dominated by Eriophorum vaginatum.

This article focuses on soil erosion and gullies. Gullies are an extreme form of soil erosion. They are physical facts with social backgrounds and consequences. They occur most often in rolling or hilly sections where rainfall is abundant, where top soil is thin and subsoil is tight, where land fertility has been depleted by exploitative farm practices. This article focuses particularly on the gullies in the Southern Regions of the United States. In the South the gully stage of erosion is common throughout the upland stretches of the old slave plantation areas of the South. Here soil depletion has been to gullies as dusk to night. The social backgrounds of the South's gullies are not far to seek: clean-culture cash crops, the unbalance between urban and rural economy, race factors, and the plantation system. The South's clean-culture cash crops have issued in gullies simply because they have persistently taken more out of the land than they have put back. These cash crops were made necessary by the credit structure of Southern agriculture, particularly cotton plantation farming.

Discusses key issues concerning soil exhaustion and fertility in the U.S. Historical significance to the agricultural industries; Analysis of pertinent topics and relevant issues; Implications on economics.

The article focuses on the importance and social implications of the principles of entomology or the study of insects. A list of principles of entomology is developed in the order of their importance for general education. Descriptions are still needed for about 10,000,000 species of insects. About 10,000 species are injurious to plants and animals. A list of very destructive insects and the annual losses in the U.S. is presented. The benefits of insects are discussed which include pollination and the maintenance of the fertility of the soil. The steps in the determination of the principles of entomology are explained.

On the basis of three years' pot experiments with various copper minerals the connexion between the relative copper surfaces of the copper minerals in question and the production of dry matter is discussed. On this basis it is made probable that it is possible to set up two main types of action of sparely soluble fertilizers added or developed in the soil. The two types are termed the »copper type» and the »potassium type». In the case of the former the absorption of the plant nutrient in question and the production of dry matter fairly soon comes to depend on the physical and chemical properties of the sparely soluble compound or compounds developed in the soil. Gradually the new-formed chemical compound dominates in the absorption of copper and the production of dry matter, because if is accumulated in relatively large quantities, amongst other things because of the comparatively small absorption by the plants and because it is not leached. Conditions are different in the case of the potassium type, where the products of weathering are fairly soon removed because of the great absorption by the plants and a possible leaching so that from year to year it is constantly the chemical and physical properties (the crystal lattice structure) of the sparely soluble fertilizers which in the main are decisive of the absorption of nutrients and the production of dry matter. [ABSTRACT FROM AUTHOR]

The article offers information on Cerrado, the principal vegetation of most of Central Brazil. It is said that the stands of the said vegetation vary in size and density of the trees, from small and scattered to large and dense. The gradient has been codified in terms of basal area of trunks per hectare and divided into four intergrading categories. It is cited that the physiognomic gradient of cerrado vegetation from stands of small, scattered trees through orchard, to well-developed woodland, has been found parallel to soil fertility gradient.

This article presents a study regarding the bryophyte succession on blanket peat following nitrogen, calcium carbonate, potassium, and phosphorus fertilizers. It discusses that there has been a considerable alteration in the bryophyte flora as a result of the various physical and chemical changes induced in the surface peat. The appearance of some bryophyte species indicated that these might be useful indicators of soil fertility. A particular experiment gave an interesting results in this respect.

Information about the papers discussed at the joint meeting of the British Ecological Society and the Association of Applied Biologists in London, England on March 11, 1960 is presented. Topics include the destruction of natural ecosystems, the monoculture of heather and its effects on hill grazings, and the effects of grass crop production on soil fertility. The event featured several ecology and biology experts including T. E. Williams, C. H. Gimingham and P. W. Richards.

The article presents several studies which assess the vegetation of serpentine rocks in Shetland Islands in Scotland. The studies show that the serpentine soil has an acetic-soluble nickel content of 90 associated with debris of chromium due to rapid weathering. The studies reveal that wind and soil instability influence the re-exposure of areas formerly under closed vegetation and colonization on the debris adapted to the environment. They conclude that the infertility of the debris is affected by the high nickel content in serpentine areas in Scandinavia and Central and North America.

The article offers information on the vegetation of sugar-cane flood fallows. It states that Demerara sugar is well known in the sugar industry worldwide. It also mentions that Demerara, or sometimes called British Guiana is not so well known, however, there are still some fifteen major sugar estates with an annual production of 200,000-300,000 tons of Demerara and other types of sugar. It also forwards that the practice of fallowing cane fields by submerging them under water for 6-12 months was first applied in Surinam, although it has long been a custom in British Guiana.

The article focuses on the influence of crop, soil, and methods of cultivation on the relative abundance of viable seeds. It reports that the weed seed population of the soil is greatly influenced by the type of crop grown, where in when the soil conditions are similar, the composition of the flora under continuous wheat and barley is very much the same, but the relative abundance of the constituent species varies greatly, some being favored by the wheat crop, and the others by the barley. It suggests that from an agricultural point of view, it is apparent that unless fallowing operations can be carried out with much greater degree of thoroughness than is usual, reduction of many weeds can be effected almost as well and more economically by intensified cultivation.

The article suggests that the rural standards of living are not necessarily closely correlated with soil or other environmental factors, and they may vary considerably in the same region at different times, as the result of migration or wars and other calamities. They often differ greatly in neighboring regions, varying sometimes with soil fertility and sometimes in the opposite direction or apparently fortuitously. In the same community, as in the southern states of the U.S., there is usually a marked contrast between them in standards of living. The prevailing standards may change considerably from one generation to another, through migration or otherwise. Topography may have more influence than soil, for in a very hilly or mountainous region it is difficult to operate a farm large enough to bring in a good income. The southern Appalachians and the Rocky Mountains both have many valleys of various widths, ranging from V-shaped ravines to flat-bottomed valleys half a mile or more wide. In the wider valleys of the southeastern mountains there are many prosperous farmers with painted houses, silos, automobiles, etc., but in the same counties the typical mountaineers in- habit the narrow valleys, and their numerous small primitive farms bring down the statistical averages.

This article presents a study on the comparison of the incidence of soil-borne diseases on winter wheat in an arable with that in an alternate ley-arable rotation at Rothamsted from 1952 to 1958. The experiments were planned to compare soil fertility and productivity under the different cropping systems, and are taking place in two fields with basically similar soil but with contrasting initial conditions. The control of eyespot and other seedborne diseases greatly improves the experiments, and can often be achieved by quite simple alterations in cropping.