Effect of Nitrogen and Shading on Yield and Quality of Grasses Grown under Young Slash Pines¹

Abstract

Tifhi‐1 bahiagrass, Coastal bermudagrass, and prostrate dallisgrass were planted in 1962, under a stand of 5‐year‐old slash pines, spaced 3 m apart and averaging 5.2 m high. We applied N at 56, 112, 224, 336, and 448 kg/ha, and enough P and K to give a 2:1:1 ratio of N:P2O5:K2O. Grass yields were taken every 6 weeks. In 1963, all grasses responded to N; maximum yields of bahia‐, bermuda‐, and dallisgrass were produced at 224, 336, and 112 kg/ha of N, respectively. N response was the same in 1964, except that bermudagrass produced maximum yields at only 222 kg/ha. No N response was seen in 1965; bahia‐ outyielded bermuda‐ and dallisgrass. In 1966, there were no differences among grasses, and no N response. In 1963, grass yields under the trees were as high as yields in the open, but in 1964, when the trees intercepted 84% of the light, they were somewhat lower. In 1965 and 1966, grass yields under trees were much lower than yields in the open. Yield decreased linearly as tree basal area increased. Crude protein content and dry matter digestibility increased with increased N rates; differences among grasses were small. Grass yields were higher than native range yields previously reported, however, the range yields were taken under different conditions of shading and fertilization. Quality of native range herbage and the grasses in this study was about the same, but quality of the improved grasses was depressed by infrequent cutting.

Planting slash pine in a dense pasture sod

“…Heights and annual height increment of slash pine as related to competition (sodded vs. cultivated) and fertilization (none vs. fertilized) following planting in a pasture sod or site prepared area I 1 Pairs of means marked with different letters are significantly different at the 0.05 level near ground line grew somewhat faster each year in the sodded treatment and by the fourth year tested significantly larger than the cultivated treatment. These growth rates were similar to those reported by Hart et al [4], Hughes and Jackson [5], and Lewis et al [7,8,10] when fertilization and cultivation had been used to accelerate growth of slash pine. It appears that the residual nutrients from previous pasture fertilization, or the genetic superiority, permitted these seedlings that were planted in a dense pasture sod to grow more rapidly than those planted in an adjacent, abandoned old-field that had become dominated by carpetgrass (Axonopus affinis) [9].…”

“…Therefore, trees were replanted and grown competition-free for 3 years before the grasses were planted [7]. Also, grasses were successfully planted in a 5-year-old slash pine (Pinus elliotti) plantation to study the effects of fertilization rates on forage yields and grass longevity under a pine canopy [4]. Then, slash pine and pasture grasses were planted concurrently where hay production was the primary crop until grazing began in the fourth year [8].…”

“…It also boosts growth of slash pine [4,5,7,15], but, high rates for pastures gave little additional benefit to pines over the lowest rate [4,15]. Therefore, any fertilization or residual fertilizer in the soil should benefit pines.…”

Integration of pines and pastures for hay and grazing

“…The proven shade tolerance of Pensacola bahiagrass over Coastal bermudagrass [6,13] could become very important when pine crowns provide more a None of the differnces were statistically significant at the 0.05 level Figure 3. Beef production from pastures planted with widely-spaced rows of pines was high since shading had a minimum influence on the grasses.…”

Growth characteristics and nutrient content of some herbaceous species under shade and fertilization

“…To the contrary, Eriksen and Whitney (1981) have found a decrease in dry matter (DM) production under shade and fertilization for six forage grasses. However, herbaceous species respond differently to various fertilization rates (Hart et al, 1970).…”