ah (VR tT 
134 
recommendation of Thaer recourse was had to the Norfolk rotation: — 4. Root-crop, 2. Barley, 3. Clover, 
4. Wheat. The clover is sown in the barley and their following a well-manured and well-cleaned root crop 
excellent results are obtained. The wheat coming after the clover is also good. Experience of the 
four course system soon showed, that clover would not succeed every fourth year, for the land 
becomes »clover-sick«. On some soils it will not succeed even with intervals of six years; nine to 
twelve years must elapse to secure a good crop. When land is »clover-sick«, the clover dies away in 
the second year of its growth, without apparent cause. Liebig regarded »clover-sickness« as due to 
the exhaustion of the appropriate mineral matters in the subsoil. Linde disputed this opinion, but it 
has again been advanced by Kutzleb. He regards »clover-sickness« as resulting from a diminution of 
potash in the soil, and, more particularly, from the absence of a sufficient amount of soluble potash in 
the subsoil. In his experiments, the potash was extracted from Lhe soil by means of water charged 
with carbonic acid. The extract from 100,000 parts of air-dried soil, was found to contain the following 
amount of potash: — 
Soil from a depth Subsoil at a Subsoil at a 
of depth of depth of 
1” inch — 6 inches. 1—2 ft. 2—A4 ft. 
.. A. 1.0924 1.7814 1.2854 
‘ Field at Wingendorf »clover-sich« | . 
6 | B. 1.0982 1.2217 LA747 
Field at Braunsdorf good clover land 2.2080 4.0395 1.4436 
Further research in this direction would be very interesting. 
Experience has also shewn that red clover cannot usually follow a crop of any plant which, like itself, 
belongs to the family Leguminosae e.g. Beans, Vetches, and other clovers (Carnation clover especially). 
Clover as Clover is an excellent preparation for cereals, especially wheat. A good clover crop, in fact, 
a preparatory implies a good wheal crop. It is not advisable to allow clover to occupy the land for two years as the 
crop. land deteriorates in the second year and the following cereal crop is nol so good. Root crops, tobacco 
and Indian corn can also be successfully grown after clover. 
WRAS WES - 
Fig. 58. 
Dodder, Cuscuta trifolii, Bab. showing dodder growing as a parasite on red-clover; 
the seed, thesyoung plant and the flowers are shown magnified 7 times. 
(After Nobbe.) 
