Abstract Rock phosphate or superphosphate band applied to slash pine about 1 year after transplanting resulted in significant height and diameter increases in 5 of 8 experiments, 3 to 5 years after treatment. However, response occurred only on somewhat poorly to poorly drained (flatwood) sands of the Groundwater Podzol and Humic Gley groups. While 50 lb N/acre applied alone usually suppressed tree growth, when applied in combination with 35 lb P/acre, it resulted in additional response. After the third year, 140 lb P/acre from rock phosphate gave about as good results as 35 lb P/acre from superphosphate. The optimum level of tissue P in current needles of 3‐ to 5‐year‐old trees was approximately 0.10%. Total soil P did not appear to be of much value for predicting response of young pine trees to added P. However, the amount of P extracted from unfertilized surface soil with 1.0 N NH 4 OAc (pH 4.8) was negatively correlated with response to phosphate applications on flatwoods sands. Curvilinear regression lines in relation to tree response to varying levels of fertilizer P with amounts of soil extractable P were constructed.
Abstract Nutrient displacement into windrows during site preparation, which followed the harvest of a natural stand of slash ( Pinus elliottii Engelm.)—longleaf ( Pinus palustris Mill.) pine, was examined on a 36‐ha flatwoods site in northcentral Florida. Almost 150 m of windrow were formed per hectare of site‐prepared area. The average width of the windrows was 4.2 m. The windrows averaged 2.5 m 2 in cross‐sectional area and occupied approximately 6% of the harvested area. Total weight of the soil, fine wood, and coarse wood components were 154, 12, and 14 t/ha, respectively. Total N, P, and K contents were 373, 18, and 27 kg/ha of harvested area. These quantities of nutrients were equivalent to the quantities which would be removed in six bolewood harvests, and represented > 10% of the site's nutrient reserves.
Abstract Eight uniform fertilizer experiments with Pinus elliottii Engelm. were established in the field between 1959–1962 on six soils ranging from excessively drained fine sands to poorly drained sandy loams. Soils from these experiments were used in pot tests, following similar treatments. Seedlings were grown for 8 months. No single measure of seedling response to treatments (height, diameter at soil surface, dry weight of tops, total dry weight) consistently correlated with field responses, expressed in terms of average tree height. There were large differences between field and greenhouse experiments in both type and degree of response obtained from the various soils. The best correlation ( r = 0.66) was between seedling total dry weight and tree height at age 7. Height of greenhouse seedlings was the poorest method of those tested for predicting field response. All results from pot experiments were more poorly correlated with tree heights in the field after 3 years than after 7 years. The role of greenhouse experiments in studying deficiency symptoms and as a diagnostic tool for determining limiting nutrients is well recognized, but results must be used with caution for predicting magnitude of fertilizer response in the field.
Synopsis Peat and vermiculite increased penetrability. Hydraulic conductivity was increased by fired clay and decreased by vermiculite and colloidal phosphate. Fired clay and peat increased noncapillary pore space while vermiculite and colloidal phosphate produced a decrease. Grass yield and quality were increased by vermiculite and colloidal phosphate treatments. Turf yield and quality decreased with an increase in hydraulic conductivity and in the force required to penetrate the soil. Bulk density was not a satisfactory index of grass‐producing ability of soil mixtures.
Abstract A clearcut forest site (45‐year‐old natural stand of Pinus elliottii Engelm. and Pinus palustris Mill.) was subjected to different intensities of site preparation to determine management impacts on N availability. Using a laboratory aerobic soil incubation technique, N mineralization potentials (N mineralizable over time) ( N o ) were determined to be 25.0, 23.3, and 17.7 µg/g for soils from an uncut control area; a burned and chopped area; and a bladed, disced, and bedded area, respectively. The N o of soil from the intensively treated area was significantly lower than the others when measured in the laboratory; however, simulations of field conditions indicated that more N may be mineralized in soils from intensively treated sites due to more favorable soil moisture and temperature conditions. Mineralization rates for these three areas, however, were not significantly different, and C/N ratios (28 and 26 for the chopped and bladed sites, respectively) for the clearcut and prepared areas did not suggest a difference in N availability. Ratios of organic matter/soluble carbon (OM/C a ) increased from 79 to 136 with treatment intensity and suggest that the N associated with the organic matter remaining on the most intensively treated site may be more resistant to decomposition. Nitrogen availability is a function of substrate quality and microenvironmental conditions. Harvesting and site treatment affected both of these. Laboratory determinations of N o appear to be a better index of nitrogen availability than C/N, C s , or total N, but do not adequately account for differences in mineralization due to treatment‐induced changes in the soil environment.
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