Five-year-old cottonwood plantation on a clay site: growth, yield, and soil properties.

A random sample of Stoneville select cottonwood (Populus deltoides Bartr.) clones planted on recent old-field clay soils at 12by 12-[00t spacing averaged 75-percent survival after five years. The growth and yield was about half that expected from planted cottonwood on medium-textured soils. Soil moisture analysis showed more height growth in years with gr~ater moisture late in the growing season. Significantly less sod N, P , K , Ca, Mg, and organic matter were in the plantation after five years than at the start . Also, no clear relationship existed between nutrient level and fifth -year average height. Cottonwood plantations have been established on more than 40,000 acres in the Mississippi River Valley (Burkhardt and Krinard 1976). Because of the expense of site preparation, planting, and firstyear culture, the species has been planted mostly where it grows best-on recently cleared ground where soil is of medium texture. Old-field clay soils are representative of poor cottonwood sites of less than 100 site index and generally have been avoided. However, growth may be improved with select planting stock. Based on limited tests, 14 select cottonwood clones were found that exceeded the growth of unimproved planting material by an average of 13 percent in diameter and 11 percent in height on Sharkey clay soil (Mohn, Randall, and McKnight 1970). Four of the clones were randomly selected as representative of above-average material and planted on a fine-textured site. The study was not designed to compare clones, which were considered to be equivalent, but to determine growth of select stock on a difficult site. This paper is a report on five-year growth and annually monitored soil properties in the plantation. The study area is located on the Mahannah 80 Plantation of the Anderson-Tully Company, Issaquena County, Mississippi. The site is an old-field with clay soils of a Sharkey-Tunica complex. The area was cleared and planted to soybeans for 6 years through the 1970 growing season. In spring 1970 prior to the last soybean crop, 3 tons per acre of lime were applied to the area by the farm management. To help in first-year weed control, the study area was fallowed in summer and early fall in 1971, and cuttings were planted in December 1971 at 12by 12-foot spacing. Clones planted were Stoneville 66, 67, 92, and 124. There were nine plots per clone, with each plot 17 rows square. Interior measurement plots were 10 rows square. The plots were dis ked four times the first year and once the second year for weed control. Heights of all measurement-plot trees were taken yearly, and diameters were taken with calipers from the second through fifth years. In March 1977, at the beginning of the sixth growing season, 120 randomly selected cut trees were measured for volume, and the stem and branches of 20 trees were weighed. Regression equations were developed using D2H (d.b.h.2 X total height) as the independent variable for outside-bark volume and total-tree dry weight and stem dry weight, including bark. The volume equation was weighted by 1/(D2H)2. Soil moisture for the midto late-growing season was determined with a neutron probe in soil moisture tubes at 1-, 2-, and 3-foot soil depths. Readings nearest July 15, August 15, and September 15 of each year were analyzed for each soil depth for the second through fifth years. At least SOUTHERN JOURNAL OF APPLIED FORESTRY two days were allowed to elapse after a rain before soil moisture measurements were made. Bulk soil samples from 0to 6-inches deep were collected from each plot at the start of the first growing season and during the first two weeks of September each growing season. Three samples were collected from the same locations within a measurement plot and a composite was made each year. Standard laboratory analyses were used for chemical determinations. (Individual plot samples were air dried and ground to pass a 2-mm sieve. Total N was determined by the Kjeldahl process. Soil pH was measured with a glass electrode in a 1: I soil/water mixture. Extractable P was determined with a colorimeter using the Mississippi soil test method (Soil Test Work Group 1974). Exchangeable K, Ca, and Mg were determined by atomic absorption spectrophotometry. Oxidizable organic matter was determined by chromic acid oxidation and titrations with Fe(NH,MSO,k Six plots were sampled for soil texture because of height differences noted during the first five years. Two plots each with above average-, below average-, and average-sized trees were sampled; two holes per plot were punched with a hydraulic probe. Soil texture was determined by the hydrometer method.