Arable Land and Pasture

As the importance of soil came to be understood, the application of agricultural lime increased. Until the middle of the 20th century, most liming of agricultural land was done using quicklime and hydrated lime products (see section 30.2). These produced fine particles of calcium hydroxide in the soil, which initially raised the pH and then reacted with atmospheric carbon dioxide to form finely divided calcium carbonate. The carbonate was sufficiently soluble to maintain the pH at the required level for a prolonged period. 

The production of large tonnages of finely divided limestone and chalk products only became economic with the development of dry grinding equipment in the middle of the 20th century. Such products are commonly called agricultural lime . To avoid confusion with quicklime and hydrated lime products, the term agricultural limestone will be used. 

A considerable amount of research has been done into the optimum pH range for various crops [10.2]. The results are summarised in Table lO.l. 

At pH levels above and below the optimum range for a particular crop, overall nutrient availability decreases, with a consequent adverse effect on quality and yield. It also follows that the effectiveness of fertilisers is maximised when the optimum pH is maintained. 

In practice, as the pH of soils tends to decrease with time, it is usual to advise liming to maintain pH values above 6.0 for grass and above 6.5 for most arable crops (the main exception being potatoes). 

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For arable land, plus urea emissions from pasture. Based on total UK fertilizer consumption (Asman, 1992) ° and 0.68 agricultural land area as arable and ungrazed grass (MAFF, 1990). ... 

The most satisfactory method for the organic farmer to reduce the risk of infection to lambs from internal parasites is to practise clean grazing, which reduces parasitic infection and increases lamb growth rate (Fig. 3.5). The most effective method of clean grazing is, as we have seen, to use a three year rotational system with sheep, followed by cattle, and then arable. This presupposes land that can be ploughed. On permanent pasture farms with no arable, beef and sheep should be alternated. To make this effective, it helps if there are as many beef livestock units as sheep. If the farm contains only sheep, then it is advisable to alternate on an annual basis between ewes with twins and ewes with singles. If the flock normally produces mostly... 

On a global scale, arable lands occupy 12% of the terrestrial ecosystems, and pastures occupy 25%. On the whole, the agrolandscapes occupy 40% of the Earth s land. At present the most used areas are in the moderate climate zone (25%) and subtropical and tropical ones (18%). To the maximal extent, natural landscapes and their relevant biogeochemical cycles are transformed into agrogeochemical provinces with a predominance of agrogeochemical cycles of many elements in Europe (>30%) and Asia (>20%). 

Ext. used land covered with vegetation, which is not or only scarcely used and not fertilized Int. used agricultural land that is fertilized strongly, e.g. arable land, pastures, and vineyards Settl. human settlements, e.g. villages, roads, and industrial areas... 

Non-agricultuial land use Grassland and pasture Arable land... 

A total of 51 fields at 24 farms were sampled dnring April, May and June 1987, of which 35 were pasture land and 16 arable land. 

In Asia, there are three important uses of land arable or croplands, permanent pastures and grazing land, and forest and woodlands. The land use pattern in the region has undergone a major change over the years with a sharp increase in cropland but a marked decline in forest. The growth in cropland is characterized by three phases (Figure 2). 

Co untry/region Total land area Arable and permanent crops land Permanent pasture Forest and woodland Other lands ... 

Arable land —Permanent meadows and pastures —Permanent crops... 

Tall oat grass is another very cotmnon grass of permanent pastures and hay meadows, and, as onion couch, it is also an important weed of arable land. Common couch occurs widely in permanent pastures and arable land but is less of a problem since the advent of glyphosate-based herbicides. 

Arable and permanent crops are grown on 7.6% of the SSA land area, permanent pasture covers a further 30.4% (FAOSTAT, 2006). The major farming systems that evolved in the diversity of African environments are described below (Fig. 1) (e.g. Dixon et al., 2001) ... 

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