Grassland ploughing

Figure 7 The estimated eontribution of nitrate from ploughed-up old grassland to eoneentrations of nitrate-nitrogen leaving soils in England and Wales in 1945. The EC limit is 11.3gm of nitrate-nitrogen. (Taken from Whitmore et...

One of the relationships iised to obtain Figure 7 was that between the amount of organic nitrogen in the soil, kg ha and the time, t yr, from the ploughing out of the permanent grassland. This was an exponential relationship derived by fitting to field data. ... 

Table 3 Effects of ploughing out of old permanent grassland at various dates. Estimated contribution in 1995 to nitrate-nitrogen in soil and, if leached, to the nitrate concentration in drainage from the soil (assumed to be 250 mm per year)...

Control of NH3 loss during grassland production presents many problems. The most readily manipulated loss is that arising from land application of slurry. Injection effectively eliminates NH3 loss, as discussed above, and is sometimes reflected in increased efficiency of utilisation of the N applied (29). On grass/arable farms, application of slurry prior to ploughing or cultivation also increases N recovery by the following crop. However, the speed with which NH3 loss can occur requires that cultivation takes place almost immediately after application (29). 

An additional benefit of injection in this context is where slurry is surface applied to pasture over a period of time resulting in the undesirable concentration of organic material at the soil surface. This is of particular concern in areas of permanent grassland where there is a surplus of slurry. Ploughing and reseeding is a costly means of treatment whereas injection will help prevent such problems arising. 

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