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manure is actually grown on the land to which it is to he 

 applied, and is so applied in an undecomposed Btate. During 

 the growth of the green crop important effects are exerted on 

 the moisture content of the soil; on the one hand the trans- 

 piration of water by the growing crop dries out the soil, and 

 light showers may not reach -its surface; on the other hand, 

 the surface of the soil is screened from the direct action of 

 frost, the beating of rain, and the sun's rays. Whether these 

 actions are beneficial or the reverse, depends, among other 

 things, on the type of soil and the time of year. 



The drying effect of transpiration will be of little consequence 

 in the cooler part of the year or on a soil well supplied with 

 moisture, but may be decidedly harmful on a light soil or in a 

 very dry season. The screening of the soil from frost and the 

 beating down of the rain may do no harm, or even be positively 

 beneficial, on a light soil, while a heavy soil may suffer by 

 being screened from frost, though it also probably benefits by 

 being saved from the beating down of heavy rain. Further, 

 the incorporation in the surface soil of undecayed plant material 

 mechanically opens up the soil, and at the same time the 

 capillary channels connecting the subsoil water with the sur- 

 face are broken. These also are effects which may be beneficial 

 or the reverse according to circumstances. A stiff cold wet soil 

 benefits greatly by the improved drainage caused by this open- 

 ing up, especially in the wet months of the year, but a light 

 sandy soil which is already too open may be harmed unless the 

 buried crop rots sufficiently quickly to lose its fibrous structure 

 before dry hot weather comes round. 



Again, even after the buried crop has thoroughly rotted, the 

 effects of its previous growth may persist and influence the 

 growth of the succeeding crop, either as a result of the drying 

 out of the soil previously mentioned, or in the case of a deep- 

 rooted green crop, by opening up the subsoil and enabling the 

 ensuing crop to draw on supplies of subsoil water which it 

 would not otherwise obtain. A striking illustration of this 

 effect of a deep-rooted green manure crop is reported by 

 Schultz, to whose pioneer work at Lupitz, in Saxony, so much 

 of our knowledge of the principles of green manuring is <1 < . 

 Schultz grew potatoes on plots which had previously been 

 green manured with lupins, and on adjacent plots which had 

 received a dressing of farmyard manure of equal nitrogen con- 

 tent. The crops of potatoes were weighed and the depth to 



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