FERTILIZERS. 



223 



FERTILIZERS. 



On the importance of different green-manuring plants in the 

 economy of soil nitrogen during the fall months, H. C. Larsen 

 {Thlsdr. Laiulhr. Flantc'ivl, 5 {1S99),jjjk 101-im).—Fot expeviments 

 wore made with the following o-reen-nianuring plants: Buckwheat, 

 yellow nuistard, field pea, eonmion vetch, hairy vetch, Roman vetch 

 ( T7(vVi mtivcv Qiarbonnensis), yellow lupiiie, blue lupine, and white 

 lupine, Medicago lupuUnd, common kidney vetch, .serradella, 2fdUotas 

 alla^ and red clover. Five pots were used for each plant. The pots 

 were filled with soil of a very light character, poor in humus and other 

 fertilizing constituents, having been taken from a tield on which crops 

 of rye, barley, three years' pasture, and oats had been grown since the 

 last manuring. An application of sulphate of potash and superphos- 

 phate corresponding to the contents of potash and phosphoric acid in 

 a good crop of clover was added to all pots. The pots were 21 cm. 

 deep and 20.2 cm. in diameter. The seeding and harrowing-under of 

 the green-manure crops were done at such a time and in such a manner 

 as would obtain in field work. Careful records were kept of the gross 

 yields and those of dry matter obtained in each case, and nitrogen 

 determinations were made in the soil in the pots at the beginning of 

 the experiments, and after the crops had been harrowed into the soil. 

 The average results of the experiments referring to the nitrogen 

 balance are shown in the following table: 



Nitrogen contcniK of pot x hcforr (iiUl after rannurlng. 



Crop. 



Buckwheat ... 



Mustard 



Field pea 



Common vetch 

 Hairy vetch... 

 Roman vetch . 

 Yellow luiiinc. 

 White lupine.. 



Trefoil 



Serradella 



Melilotus 



While buckwheat and mustard caused an appreciable loss of nitro- 

 gen as compai'ed with the content in the bare soil, the legumes supplied 

 -t to 5 times as much nitrogen as these crops, and made the soil con- 

 siderably richer in nitrogen at the end of the experiments than before, 

 the increase corre.-^ponding to about 15 loads of barnyard manure per 

 acre. 



The pots were placed under cover over winter, and in the spring 



