li*0 ArPENDix. 



difl bare bare ground. (5) In the spring it catclaes soluble nitrates that might 

 leach out of the soil before active root action of the trees begins. (6) It pumps 

 the surplus water out of the soil early in the spring so that the ground warms up and 

 may be plowed earlier than if no cover crop were used. (7) When plowed under these 

 crops add enormous amounts of vegetable matter or humus to the soil. The 

 humus improves the mechanical conditif.n of the ground by loosening up the soil 

 particles ; it increases the water-holding power of the soil, provides a favorable 

 home for soil bacteria, furnishes elements cf plant food in available form, and 

 assists in breaking up chemical compounds of plant food which would otherwise 

 remain unavailable. (S) Experience has shown that the continued use of cover 

 crops will, to a certain extent, make heavy land lighter and light land heavier. 

 This is of immense advantage in practical orchard operations 



PLANTS TO USE. 



The plants used for cover crop purposes may be placed in three classes, 

 namely, the nitrogen gatherers, the potash plants, the ordinary ones used without 

 special reference to the addition of plant food to the soil, as rye, oats, buckwheat, 

 and perhaps weeds. 



The nitrogen gatherers are so named because they are associated with spe- 

 cial forms of bacteria of the soil which extract free nitrogen from the air and 

 store it up in the tubercles on the roots. The nitrogen so stored is in an organic 

 form and after the death of the plants soon becomes available food for other 

 plants. These are also called leguminous crops, and are the cow peas, soy beans, 

 clovers, vetches, alfalfa, Canada peas and velvet bean. They store up varying 

 amounts of nitrogen, potash and phosiihoric acid, the amounts being influenced 

 by climatic and soil conditions. This class of plants can be used to great ad- 

 vantage to improve soil more or less poor in humus and the nitrogen compounds. 



The term "potash plants" may be a misapplication of the term, but there 

 seems to be much justification in its use from the large amount of potash found 

 in these plants as will be shown later on in this report. Under this head 

 come the turnips and rape. They are especially useful on soils that are abund- 

 antly supplied with nitrogen and humus. 



I. EXPERIMENTS IN 1901-2. 



In 1001 the Experiment Station began a comparative test of cover crop 

 pl.'ints in three localities of the State. The soil conditions of each place were 

 quite different from those of either of the others. At the Experiment Station 

 the test was on a heavy clay loam which partially represents much of the land 

 of New Castle Coimty At F. M. Soper's, Magnolia, the soil is a sandy loam 

 that has had but little of cover crops or manure turned under for fifteen years. 

 The third place, that of S. H. Derby. Woodside, was similar to the soil just men- 

 tioned, but has been much Improved by having crimson clover plowed under an- 

 nually for al)out fourteen years. 



These experiments were planned by Professor G. Harold Powell, then Horti- 

 culturist of the Experiment Station. Professor Powell accepted a position with the 

 I'nited States government soon after the seed for these crops was sown and the 

 experiment came under the charge of the writer late in Octobei". It was co- 

 operative work with the Bureau of Plant Industry furnished the seed and the 

 ment of Agriculture. The Bureau of Plant Industry furnished the seed and the 

 F^xperiment Station did the work of conducting the tests. The object was to de- 

 termine which crops would succeed best under various soil conditions. 



TESTS AT THE JIXPEUIMKNT STATION. 



Since the Station has a very limited area of land the plots for each crop or 

 combination of crops were necessarily small. They will, however, serve as an in- 

 dication of what may be expected in Northern Delaware. These cover crops were 

 grown in an orchard containing peaches, plums, cherries and pears. The ma- 



