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



NURSERY INVENTORY 



In order that nursery and field planting activities can be properly 

 coordinated, an inventory must be made to determine the probable 

 nursery production in various blocks and species of stock. 



To determine the approximate percent of count necessary in deciau- 

 ous nurseries, and also the length of counting plots, a 100-percent 

 count was made of all the seedlings in 9 rows, each 600 to 700 feet long, 

 and the number recorded foot by foot. The number of seedlings per 

 lineal foot of row ranged from to 40 but fell mostly between 4 and 12 

 per foot. By means of a statistical analysis of the data, made by R. H. 

 Blythe, Jr., of the Lake States Forest Experiment Station, a 1-foot- 

 long counting plot was found to be satisfactory; and for an average 

 block of 5 to 10 acres to the species, a total of 250 to 300 1-foot plots 

 well distributed over the block invariably insured an accuracy of 

 ±10 percent. From 900 to 1,000 plots were required for an accuracy 

 of ±5 percent. In other words, on a 10-acre block with a space of 

 about 2 feet between rows, a 1-foot counting plot taken mechanically 

 every 200 feet in all rows would usually give the desired inventory 

 within ±5 percent. This amounts approximately to a 0.5-percent 

 count. If a number of species are involved, a separate count should be 

 made for each species. 



Where blocks of stock are comparatively small, or where there is a 

 considerable lack of uniformity of stand, best results have been ob- 

 tained by taking mechanically a 1-foot counting plot every 100 feet. 

 This is the equivalent of a 1.0-percent count. It is very important 

 that the counting plots do not appear on lines across the direction of 

 the rows but that they have a dispersed pattern. This can easily be 

 assured by using a steel tape or rope of 100-foot length to locate the 

 counting plot and by using a cumulative total of counting plots ob- 

 tained by going down one row and doubling back on the next row. 



If the seedlings have a density ranging from to 12 per lineal foot, 

 the accuracy is considerably higher with the same percent of count. 

 Analysis of data taken where this range of density occurs indicated 

 that a count of 250 plots selected at random gave accuracy within 

 ±5 percent and that 100 to 150 plots gave an accuracy within ±10 

 percent. 



Care should be taken in laying out the 1-foot counting plot so that 

 only the seedlings within the 1-foot distance are counted. For this 

 purpose a foot rule is used or a counting frame is made. The latter 

 consists of a wooden or metal bar with two 6-inch-long tapered spikes 

 or rigid thin metal rods fastened to it parallel to each other, 1 foot apart, 

 and at right angles to the longer bar. This frame is pushed up against 

 the seedling row so that the spikes or rods project through to the other 

 side, thus sharply delineating the ends of the 1 -foot-long counting plot. 



If counting plots are selected at random, bias should not enter into 

 the location of the plot, and it should be a strictly random sample. 

 The practice of some commercial nurserymen in making the counts 

 on zig-zag lines roughly representing two diagonals drawn through 

 the nursery block of a given species is fairly satisfactory, but generally 

 will not give so high a degree of accuracy as the mechanical sample 

 taken at 100- to 200-foot intervals. 



