642 EXPERIMENT STATION RECORD. [Vol.38 



trees and the grass cut and let lie; the grass cut and allowed to lie where it 

 falls, no additional mulch given the trees; and the grass cut and raked up to 

 form a mulch collar ahout the trees. Combinations of these systems of manage- 

 ment are also being studied on certain plats. Portions of certain plats are also 

 being fertilized to determine whether lack of any particular fertilizer should 

 be taken into account in interpreting the effects of different systems of soil 

 management. In addition to determination of soil temperatures and soil mois- 

 ture, physical, chemical, and bacteriological studies are being conducted. The 

 experiment is described in detail, and the results of the different systems of 

 culture, both with reference to the tree and with reference to the soil, are pre- 

 sented in a series of tables and fully discussed. 



Among the results thus far secured the authors found that there have been 

 no wide variations in phenological behavior of trees under different systems of 

 soil management, yet there does occur a marked slacking up of gi-owth on grass 

 plats during the dry periods in summer. Trees grown under a clean culture- 

 cover crop system or under a heavy mulch made 44.5 per cent greater average 

 yearly gains in trunk girth than trees grown in grass with a light mulch or no 

 mulch at all. There has been no significant difference between the three 

 varieties in their response to soil management treatments. The Staymau 

 Winesap made slightly greater trunk girth on all plats than either Grimes or 

 Jonathan. 



The authors point out that the effect of the various systems of soil manage- 

 ment on the soil moisture as observed in this work can not be directly applied 

 in the abstract to the humid region in general. The soil in the experimental 

 orchard has a low organic content and high proportions of silt and clay, thus 

 making it one through which water percolates slowly and one which is easily 

 puddled. In this soil, mulching, either by cultivation or by using a heavy 

 supplemental mulch, maintained the percentage of soil moisture to more than 

 twice that of grassland during the two June droughts of the five years. These 

 soil moisture conditions are closely correlated with the girth increase made by 

 the trees. A study of the precipitation data obtained indicates that the vari- 

 ation in growth due to seasonal moisture conditions has been quite as large 

 as that due to cultural practices. 



Data secured in the soil temperature studies do not support the opinion that 

 rains are an important adjunct in warming the soil. The single factor of soil 

 moisture does not appear to have had an influential bearing upon the tempera- 

 tures existing under the different systems of soil management. The tempera- 

 ture range varies inversely with the amount of mulch covering the soil. As 

 far as this experiment is concerned the r61e of soil temperature within the 

 limits of ordinary cultural practices appears to be a neutral factor in tree 

 growth. 



Among the chemical changes induced in the orchard soil by cultural practices 

 during the period 1910 to 1915 it appears that clean cultivation tends to deplete 

 the soil of its organic matter, despite the fact that a cover crop is being turned 

 under each year. Organic matter has slightly increased in the straw mulch 

 plat. The sod plats as a whole have come nearer to holding their own in 

 volatile matter, humus, and nitrogen than the clean culture-cover crop plats. 

 There was no apparent correlation between the amount of volatile matter, 

 humus, and nitrogen in the soil and tree growth. 



In most cases more bacteria were present in the sod plats than in the clean 

 culture-cover crop plats. Variations in the amount of mulch on the sod plats 

 have some influence on bacterial numbers. There appears to be no correlation 

 of tree growth and soil moisture with bacterial numbers. Ammonification 

 yaried with the season. Differences between plats are not consistent with 



