THE PRODUCTION OF WHEAT 25 
Manuring cereals then ceased, until it was found that 
the warmer and drier summers experienced here allow 
of the nitrification of the waste organic matters in the 
soil to such an extent as to provide a sufficient supply 
of nitrates for satisfactory plant growth. 
In the search for the element necessary for plants 
and least plentiful in the soil, phosphorus was some 
ten years ago found to be of great advantage, and phos- 
phates are now being used to an increasing extent 
to counterbalance the exhaustion of the soil due to 
cropping. 
(2) Indirect—The indirect method is of special 
importance to New Zealand conditions; for the Dominion 
is very well adapted to mixed farming. Two ways of 
employing this method may be used, by a system of crop 
rotation or by the grazing of animals on wheat lands. 
In practice they are employed together when opportunity 
offers. There are various systems of crop rotation, but 
it will suffice to describe one and point out its advantages. 
A rotation may begin with a root crop, usually turnips, 
manured with phosphates. This crop not only gives an 
opportunity for cleaning the land but it provides 
excellent winter feed when supplemented by hay or, 
more commonly, wheat straw. The residue left then 
provides an excellent manure. After the turnips are 
eaten off the farmer prepares the soil for a crop of 
barley or oats, as it is now too late to sow wheat. The 
land is ploughed, but the ploughing is only a shallow 
one, so that the water stored in the deeper layers of the 
soil which have been solidified by the trampling of the 
sheep may not be disturbed. Clover and grasses are 
sown among the barley or oats so that they may take 
firm root whilst the latter is growing and ripening. The 
crop is harvested in the autumn, and the young clover 
and grasses establish themselves during the autumn or 
winter, and produce a crop of hay the following year. 
This is harvested in midsummer, and the aftermath 
forms an excellent autumn grazing for the sheep and 
cattle which are to be fed the next winter. 
In the autumn the ground is ploughed again, and 
