The Effects of Fertilization on Diameter Growth in Dense Stands of Ponderosa Pine in Arizona

In 1961, fifty 1/5-acre plots were established near Blue Mountain in Arizona by Professor R.F. Wagle for the purpose of testing a selected group of fertilizers, a herbicide and a growth hormone in overcoming stagnation in Ponderosa pine stands. Thirteen treatments were applied at random on the plots. Nitrogen, phosphorus, potassium, fenuron, gibberellic acid, along with a select group of microelements were applied on the plots. Tree growth was measured at the end of each growing season by use of a dendrometer or growth band. The growth band measured circumference growth to 0.01 inches. Diameter measuements were made in 1961 and 1973 using a diameter tape. Diameter measurements were estimated to 0.01 inches. The data were analyzed using Student-Newman-Kuels’ test. The analyses were performed at the 95% confidence level. The results indicated that stagnation cannot be broken using fertilizers without thinning when the stand and site characteristics of the type present in this study exist.