54 EXPERIMENT STATION BULLETIN 351 



farm at Northwood and tests of various rotations on the Tasker farm at 

 Center Strafford. In the latter case the soil had been depleted by constant 

 tillage to the extent that it maintained no earthworm population, indi- 

 cating no beneficial effects from micro-organisms in this soil. The Piper 

 farm, on the contrary, represents a soil high in organic matter and of ex- 

 cellent soil structure. In this case, the purpose is to determine changes in 

 organic matter and soil structure during the process of depleting the soil 

 by continuous culture, and by using rye as a winter cover, compared with 

 other crops in rotation. On the Tasker field the aim is to note changes 

 as they occur during the process of actually building up soil structure and 

 organic matter b\' introducing a system of crop rotation. 



Due to changes in personnel and to labor shortage, the determination 

 of organic matter and changes in soil structure bv analvtical laboratory 

 methods have necessarily been suspended temporarily. The field w^ork, 

 ho\\"ever, is being continued and consists mainly of keeping temperature 

 and rainfall records, measuring run-off and soil losses, harvesting pota- 

 toes, seeding rye and other crops in the experimental plots, and the like. 



P. T. Blood, F. S. Prince 



The Influence of Soil Texture, Soil Moisture, 

 And Soil Aeration upon the Growth of Plants 



During the winter of 1942-43, work was continued with potatoes in 

 soil cultures. The same three soil t\pes as used previously were Buxton 

 clay, Newmarket fine sandy loam, and Merrimack loamy fine sand. Po- 

 tatoes were grown in each t\pe in galvanized pails at a constant soil 

 moisture content. Each soil was sifted into three size fractions, as fol- 

 lows: fine, below 0.25 mm.; medium, 0.25 to 1.0 mm.; and coarse, all par- 

 ticles above 1.0 mm. Five plants were grown in each of these fractions 

 and five plants in natural, or unsifted soil of each type. Each soil fraction 

 and type was tamped to attain a 55 per cent total pore space as nearlx' as 

 possible. This was about the only mutually similar amount of pore space 

 attainable throughout the three soils types. All were grown at a luoisture 

 content of 75 per cent on the calculated basis as in the previous \'ear. 

 Plants were grown to full maturitv instead of being harvested at 90 davs 

 as previously. A summary of the results follow: 



Yields of Potato Tubers in Grams Grown in Different Soil Textures 



Texture size 

 Soil type Natural Coarse ^^edium Finei 



Merrimack loamy tine sand 1691 1586 2333 3910 



Newmarket fine sandy loam 3944 3830 3890 4038 



Buxton clay 3463 3607 3319 2527 



Since moisture content was optimum and constant and since total 

 pore space was constant, it appears that texture alone, aside from air in the 

 soil, affects plant growth and yield considerabh'. The \ields tend to de- 

 crease with greater particle size in the .Merrimack or coarse textured soil 

 and to decline to some extent in the other extremes, or the finer clay frac- 

 tions. Apparently, particle size ma\' var\' within quite \\ide limits in a 



