391 



But an excess of nitrogen directly promotes decay, while that of calcium 

 phosphate has an opposite effect. I planted in sandy soil, in alternating 

 rows, pieces of healthy tubers from three varieties as different as possible 

 and also pieces from tubers suffering from hlack dry rot^. This field was 

 divided into two halves absolutely similarly planted, of which one was given 

 large amounts of Chile saltpetre on all the rows, the other Thomas slag. 

 In the healthy seed, in the half fertilized with Chile saltpetre, the tubers 

 sprouted very imperfectly while almost all the diseased seed had decayed. 

 The results obtained in the plot fertilized with Thomas slag were directly 

 opposite. There the diseased seed yielded very uniform healthy plants. 



In the last named plot, plants from health}'- and diseased seed of all 

 varieties developed shorter shoots with more highly colored foliage. They 

 ripened more rapidly and the han-est was nearly twice as large as from 

 the plot fertilized with Chile saltpetre-. 



With this might be associated also the phenomenon well-known in 

 practical circles as iron spottedness or the multi-colored condition of pota- 

 toes. Tubers outwardly normal have brown or brownish-gray places in 

 their tissue in the fresh cross-section. In this, the rest of the flesh can be 

 perfectly healthy and remain white, or, exposed to the air, may quickly 

 assume a rusty red color. The spots originally discolored have brown, 

 dead cell walls and many still contain starch. Often, and, in fact, when 

 the cut surface subsequently turns red in the air, only traces of starch may 

 be found in the diseased centres, but sugar is found instead. 



While some observers think the iron spottedness must be traced to an 

 abundance of acid iron compounds in the soil, others are inclined to be- 

 lieve dampness to be the cause. Many discoveries show, however, that 

 heavy fertilization with stable manure caused the iron-spotted condition in 

 certain varieties, which, in the same year, with chemical fertilization, re- 

 mained healthy^. Tubers which turn red, when cut, are found most fre- 

 quently where an abundant nitrogen fertilization is used. Hence one is 

 justified in considering a multi-colored condition of the flesh to be an indi- 

 cation of nitrogen over-fertilization. Tubers with iron spots, as a rule, 

 yield healthy plants in the following year. 



Chile Saltpetre W^ith Woody Plants. 



Janorschke* has investigated the phenomena of nitrogen fertilization 

 without the addition of calcium and phosphoric acid. He found that plants 

 with multi-colored leaves became greener for the first year or two. In 

 dwarf fruits the branches continued to grow almost without interruption 

 until August and even later, which thus prevented the setting of the blossom 

 buds. Attention should also be called to the fact that the effect of the fertilizer 



1 Zeitschr. f. Pflanzenkrankh. 1894, p. 12G, und 1895, p. 98. 



2 Zeitsch. d. Landwirtschaftskammer f. d. Prov. Schlesien 1899. 



3 s. Jahresbei'jchte des Sonderausschusses fiir Pflanzenschutz, herausgegetaen 

 I. Deutsch. Landw.-Ges. 



4 Zeitschr. d. Landwirtschaftskammer f. Schlesien 1898, No. 34. 



