35 



the next year's planting. The common red clover and sweet 

 clover possess an advantage over mustard, as their roots are pro- 

 vided with nitrogen-containing nodules, the product of bacterial 

 activity (see Fig. 1.) In this case a certain amount of nitrogen 

 is added to the soil, whereas with such crops as rye, mustard, buck- 

 wheat, etc., no such bacterial adaptation occurs and the soil nitrogen 

 will not be increased from atmospheric sources. The legumi- 

 nous plants constitute the best catch crops on account of the 

 peculiar nutritive adaptation existing between the nodular bacteria 

 and the atmospheric nitrogen. A crop of these plants can be 

 sown and just before reaching maturity they can be cut, and, if 

 necessary, fed to stock. The roots containing organic matter and 

 a store of nitrogen can be plowed under. We have practised this 

 system in our greenhouse to good advantage, a practice which, as 

 far as we know, is not made use of in greenhouses to any extent. 

 During the summer the greenhouse which is devoted to winter 

 cucumbers and lettuce generally lies idle, and by sowing a crop 

 of white lupine (which will develop in about six weeks under these 

 conditions), or some other legume we succeed in adding to our soil 

 a needed supply of organic matter and nitrogen. Experiments 

 have shown that a crop of legumes plowed under is practically 

 equal to a normal supply of nitrogen to the soil (see Fig. 2). 



A certain stage of development in the crop is necessary in order 

 to obtain the largest supply of nitrogen. This stage probably coin- 

 cides in most cases with that when the seed are maturing. There 

 have been a considerable number of leguminous plants grown for 

 test purposes at the Hatch Experiment Station, in Amherst, during 

 the past ten years or more, such as the white lupine, horse bean, 

 serradella, alfalfa, soya beans, melilotus, Canadian pea, and the 

 various clovers, etc. Unfortunately, however, the majority of 

 these winter-kill in our climate, and only a few of them can be 

 used for winter-soil covers. Among those best suited for our 

 climate is the common red clover and the melilotus or sweet clover. 

 The latter, when sown in July or at the time of the last cultivation 

 of the soil, is capable of attaining a height of twelve to fifteen inches 

 the following May, at which time the crop can be cut and utilized, 

 and the nitrogen-containing roots can be plowed in. The red clover 

 is also useful as a soil cover but does not always make sufficient 

 growth in time for spring planting, it being considered by some 

 to be less desirable on this accouut than the melilotus or sweet 

 clover. The crimson clover is used as a soil cover and for green 

 manuring extensively in the south, where it is hardy, but repeated 

 trials have shown that it cannot be depended upon in Massachu- 

 setts, although it is not improbable that it might winter on some 



