58 EOOT-KNOT AND ITS CONTROL.. 



todes remove the different minerals almost equally, so that only 

 where one element is rather deficient will the addition of that alone 

 be of benefit. The sugar-beet nematode removes large quantities 

 of mineral food from the roots, so that unless these minerals are 

 present in the soil in considerable excess over that naturally needed 

 by the crop the plants will suffer from lack of that mineral which is 

 not sufficiently superabundant. Thus, an amount of potash sufficient 

 for a healthy crop may be insufficient if the sugar-beet nematode is 

 present, and the symptoms of potash hunger can be averted only by 

 applying an excess of potash. Probably this is also true of the root- 

 knot nematode. The sandy soils of South Carolina are rather potash 

 poor, so that a diseased plant will suffer from potash hunger, while 

 the other elements may be in sufficient abundance. At any rate, 

 the addition of potash in excess proved helpful. The nitrogen- 

 containing fertilizers when not in too great excess also benefited the 

 plants somewhat, but not so markedly as the potash. This is to be 

 expected, as nitrogen is not any too abundant in those soils. The 

 phosphatic fertilizers, however, showed no benefit at all. 



Caution must be taken not to apply too much potash. In 1907, 

 in fact, kainit at 1,000 pounds per acre was harmful in that many of 

 the young seedlings were killed, necessitating replanting several times 

 in order to get a fair stand. This quantity was not harmfid in 1906 

 on another plat, showing that the danger limit is probably not far 

 below that amount. Muriate of potash at the same rate was very 

 harmful in 1907, as was also the same amount of ammonium sulphate. 

 Potassium sulphate, 667 pounds to the acre, and potassium magnesium 

 carbonate, 667 and 1,333 pounds to the acre, were absolutely harm- 

 less, while the latter amount of potassium sulphate was only 

 slightly harmful. 



In spite of the high fertilization a field continually planted to 

 nematode-susceptible crops will, if the nematode is present, eventually 

 become so infested with that parasite that it will be impossible to 

 make paying crops. However, it can not be denied that for special 

 occasions it is of value to reduce part of the evil effects of the nematode 

 infestation by high fertilization. 



FLOODING. 



The objections to flooding the soil that would apply in the case of 

 land occupied by permanent crops do not hold good in fields devoted 

 to annual or short-period crops. In the former case the soil can not 

 be kept submerged longer than a few days or the roots are killed. 

 In the latter case, however, the fields can be flooded for as long a 

 period as desired before the crops are planted. There is no doubt 

 that under such conditions flooding has value. This has already 



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