88 MISC. PUBLICATION 43 4, U. S. DEPARTMENT OF AGRICULTURE 



0.25 inch at a point 2 inches above the ground line. To this the 

 nurseryman will add the quality objective of solid, woody, well-rip- 

 ened stock with well-branched, compact root systems. 



In this endeavor, account must be taken of the long growing season 

 in the South as against the comparatively short season in the North, 

 and the rapid rate of growth of such species as Chinese elm and black 

 locust in contrast with the slower growth rate for species like green 

 ash and hackberry. In all cases, it is best to encourage full, unretarded 

 growth during the first half of the season and to reserve the control 

 measures for the latter half of the season. Otherwise the nurseryman 

 may be faced with the necessity of forcing the seedlings in the latter 

 part of the growing season, and so cause them to remain soft and 

 succulent late in the fall and difficult to harden off properly. Such 

 seedlings are more subject to injury from occasional early frosts, are 

 more difficult to handle in storage, and are more subject to desiccation 

 in drought periods, with consequent great reductions in survival. 



MOISTURE REGULATION 



With optimum stand density and soil fertility, control of growth 

 becomes largely a matter of moisture regulation. If an abundant 

 supply of soil moisture is well distributed throughout the season, 

 growth will be fairly consistent and, barring early frosts, will continue 

 until late in the fall. Under such circumstances, the top growth rate 

 of the seedlings may materially decrease during the heat of the summer 

 but it will increase again during the cooler early-fall months, particu- 

 larly in the Southern States. Therefore, for species that need to be 

 held back or retarded, cultural practices open to the nurserymen 

 during summer are: (1) Stopping all irrigation, and (2) hastening 

 depletion of the soil moisture by discontinuing all cultivation, thereby 

 packing the soil. Conversely, the opposite practices will force growth 

 to continue. 



Certain species such as green ash, honeylocust, and coffeetree 

 need to be forced continuously by irrigation and cultivation during 

 the hot summer months. These species are prone to "set" their 

 terminal buds upon the advent of unfavorable growing conditions; 

 once these buds are formed, the seedlings seldom start height growth 

 again until the next season. Therefore, careful and frequent checking 

 of soil moisture in various parts of the nursery to a depth of at least 1 

 and preferably 2 feet is essential. It is much more important to check 

 moisture condition at many places in the nursery, even if only by 

 estimation or rough field methods, than to obtain a very accurate 

 record for one or two spots which may not be representative of the 

 nursery as a whole. 



Moisture content of soil can be gaged by oven drying, by the use of 

 various instruments, or by estimation. It has been found 14 that 

 nurserymen can quickly learn to estimate closely the available 

 moisture content of a soil by feeling of it and judging its cohesiveness. 

 After such estimates are made, from samples taken to a depth of a 

 foot from various places in the nursery, the samples are placed in 

 tight cans or small glass jars with covers and later weighed. A 

 portion of the sample is dried for 12 to 24 hours in an oven at 210° to 



'4 STOECKELER, J. H. MEASURING SOIL MOISTURE CONTENT IN THE FOREST NURSERY. U. S. Forest SerV. 



Lake States Forest Expt. Sta. release. 4 pp. July 30, 1937. [Mimeographed.] 



