THE PRODUCTIVITY OF WOODLAND SOIL 509 



Pine, become open while maturing, they should be underplanted 

 to protect the soil — for diminution of its productivity means 

 diminution of its capital value, as well as a decrease in the 

 annual return it is then capable of making through timber- 

 production. And if it does not pay to underplant such a crop, 

 it is worth considering whether it is not then better to realise 

 the existing crop (even if not yet fully mature), and raise a 

 fresh crop of a more profitable kind. In the Beech-woods that 

 are about to be regenerated naturally, it is always advantageous 

 to expedite the decomposition of the top layer of raw humus 

 by tearing up the soil with strong roller-harrows, and thus 

 preparing it also for the reception of the seed. Treated thus, 

 the dead foliage is brought within better reach of the earth- 

 worms, saprophytic fungi, and other organisms assisting in 

 the process of decomposition. But in the replanting of areas 

 covered with heathery raw humus, the heathery crust of about 

 eight inches is broken through with a plough to mix the soil 

 and the subsoil, or strips are cleared of heather and deep pits 

 are bored with conical spades for planting. 



A different problem, however, has to be solved when the 

 question deals with the planting of poor waste lands, where 

 there is a total absence of the good leaf-mould so favourable 

 to soil-productivity in timber-growing. Even though wet or 

 water-logged moorland be drained so as to render it plantable, 

 yet the nitrogen it may contain may be inert and not available 

 for the purposes of tree-growth owing to the absence of the 

 micro-organisms abounding in soil fertilised by good leaf-mould. 

 And it is probably also mainly due to this same reason — the 

 want of any admixture of good humus — that Pine and Spruce 

 are so apt, almost so certain, to become liable to fungous root- 

 diseases when planted on fields thrown out of arable cultivation. 

 Except in the case of trees like Robinia and Alders, which 

 collect nitrogen in their root-nodules, there can be no sufficient 

 supply of nitrogen without humus ; and without an ample 

 supply of nitrogen a soil cannot be so productive as it otherwise 

 might be, judging merely from its mineral composition. 



Strikingly successful results have been obtained on the 

 heathery, sandy waste of Liineburg (Prussia), both by fertilising 

 the poor sand with peat, and by sowing 1 kilo, of Robinia seed 

 per hectare along with 4 kilos, of Scots Pine and ij of Spruce 

 seed. Or else the Robinia is planted in advance, and the 



