is necessary makes the natural food production better available to the fishes. The 

 raaintenance of the pond and of the health of the pond fishes are not less important 

 tasks of r-eed and weed removal. Experiments in Wielenbach in 192/i have shown that by 

 the removal of above-v.ater plants the yields of fertilized ponds were on the average 

 about 56.4 kilograms per hectare higher than in un -mowed ponds, which had an average 

 natural grov/th of 136.8 kilograms per hectare, Roessler announces, that in Cma Ulaka, 

 the yields in fertilized mowed-out ponds in 1928 were about 79 percent, in 1930 about 

 56,8 percent higher than in fertilized comparison ponds which were not mowed out. 



For the in.-nediate removal of above-water plants they should be mowed regularly 

 and closely above the pond bottom. This is undertaken in the period from the beginning 

 of Uay or June to the beginning of August and at least three times a year if possible. 

 Unfortunately there are no more exact investigations available upon the various re- 

 actions of cutting of the many kinds of water plants in consideration, upon the various 

 actions of cutting above or just belovr the water surface or on the pond floor, and 

 upon the variable action in individual months. These kinds of important investigations 

 should actually form the foundation of all plant control methods in the pond. The 

 question of plant control in the pond has all along been treated in a too strongly 

 generalized way, I have observed fi-om experiments that many plants in certain stages 

 can least endure a cutting above water, Heyking announces that the most sensitive 

 places are 25 centimeters belov; the water surface. Practical experiences finally have 

 shovjn that cutting at the ground almost always works best. Besides it is repeatedly 

 sho>v:i that reeds especiaJJy must be mowed three times if possible (the first time in 

 the beginning of Llay) for lasting shortness and for the most complete destruction. 

 Reeds suffer greatly even from one mowing in the beginning of August. Sedges, if the 

 cutting is to be successful, must be mowed as early as the beginning of June, Mth 

 most above-water plants another cutting after mid-July should not be omitted, because 

 cutting Lmmediately before blooming is frequently most effective. With earlier cutting 

 the plants always grov; again. Of course, the seccnd cutting is thereby made easier. 

 Besides this, the earlier cutting should not be spared, because otherwise the damage 

 from the above-v;ater plants lasts too long. From August onward, if the reed was not 

 movred previously, it becomes very woody; late mowing becomes expensive. Unfortunately, 

 where agriculture and pond culture are interwoven, the harvesting work often hinders 

 a July cutting. Furthermore, the destruction of above-water plants is in part also 

 the task of ground cultivation. The regular cutting, however, is by far the cheapest 

 manner of attack. The restoration of strongly reeded and deposited ponds is expensive 

 and most unprofitable as the war period has shown. Regarding the influence of pond 

 depth upon reed formation, compare Chapter 1, E, U> 



The mowed above-water plants may be left lying in the pond, provided they are not 

 too rich in cellulose and that there is no danger of gill rot disease or oxj'gen impover- 

 ishment. The layering of the mowed material upon the reed stubble favors its further 

 destruction and delays the after growth of the reeds, Kisker announces that experi- 

 ments by Aim have sho^^•n that a thirty day shading in June and July causes reeds, water 

 plantains (Alisma), and green algae to perish completely. If the mowed off above- 

 water plants are to be taken out, which naturally causes expense, it is best to carry 

 them to a suitable location and then pile in heaps on the bank or, better still, right 

 in the pond. The heaps, which can still be formed in the autumn, may be layered 

 throughout with lime as is customarj' with compost heaps. 



In the removal of excessive amounts of under-water plants, which primarily serves to 

 combat all too strong shade formation, it is obviously necessary to pull out the mowed 

 weeds . 



The Lmplements and machines for cutting above-water and under-v/ater plants will now 

 be discussed in the following. 



One of the simplest though most important of implements, is still the hand scythe. 

 For reed cutting, it must be selected not too long and not too narrow, so it will tend 

 from its own weight to lie well on the bottom. There should be a larger space between 

 the neck and blade of the scythe to prevent repeated gathering and wedging of above- 

 water plants from retarding the mowing. The plartts are cut off mainly by short jerky 



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