PLANT HYGIENE. 



77 



from maiden-loam and leaf -mould, incorporated stable-manure and 

 ashes, but used very little else. They dunged, limed, and dug their 

 gardens, and grew hardy plants. To-day we have innumerable 

 fertilizers of a highly forcing character. Eightly used they are 

 gigantic forces in the hands of the cultivator, but what knowledge 

 and experience are required ! Consider the case of a cabbage or lettuce 

 planted in autumn to stand the winter. If it be planted in too rich 

 soil, it will make succulent growth and fall an easy prey to frost. But 

 if grown in a soil not too rich, but very firm, it will stand the many 

 different samples of weather so characteristic of our English climate. 

 Then, when milder weather comes, or a short time before it is wanted, 

 a small quantity of nitrate may be given, and possibly a stirring of soil. 



The liability of plants fed too highly with available nitrogen to 

 frost injury was shown in the winter 1908-9. I had about 450 yards 

 of sprouting broccoli ; three rows were manured the whole length 

 with ammonium sulphate at the rate of one hundredweight to the 

 acre; the adjoining plot was treated in every way similarly, except 

 that the ammonium sulphate was omitted. The frost destroyed 

 practically every plant in the manured strip, but did no harm on the 

 adjoining plot. A raspberry plot near by gave similar results ; the 

 thick succulent stems were destroyed, but those which had not 

 received the extra nitrogen remained quite uninjured. This season 

 I have grown a long strip of thousand-head kale (the hardiest cultivated 

 Brassica), and by its side a strip of sprouting broccoli. Ammonium 

 sulphate was applied to the kale at the rate of two hundredweights to 

 the acre, and the result is now shown by much damage from frost; 

 the sprouting broccoli remains uninjured. Gooseberry bushes properly 

 summer-pruned and suitably manured with mineral-manures, but 

 limited nitrogen, have well-ripened wood, and have resisted mildews 

 quite effectively, whereas an application of nitrate ensured trouble of 

 some kind. 



An excess of potash fertilizer may do little or no harm. The ill- 

 effects occasionally seen after adding phosphatic manures is due to the 

 accompanying substances, such as unneutralized acid. An excess of 

 lime may put such calcifuge plants as rhododendrons, lupines, and 

 sorrels decidedly at a disadvantage, but otherwise the ill effects are 

 usually nil, and much more frequently great benefit follows from 

 application of lime than the reverse. A marked deficiency of available 

 nitrogen will almost arrest the growth of such plants as Brassicas. An 

 excess of nitrogen will force vegetative growth to an enormous extent, 

 resulting in elongated, thickened, succulent stems and leaves, and 

 such plants will fall an easy prey to frost or pest. It has Been well 

 said " All other things being equal, he will be the most successful culti- 

 vator who always has sufficient available nitrogen for his plants and 

 none to spare." Nitrogen, as is well known, exists in the free state in 

 inexhaustible supphes in the air; but this is useless for plants except 

 indirectly by the aid of microscopic life, or when brought into a com- 

 bined form by chemical means. 



