Synopsis
Grass yields responded strongly to yearly applications of up to 400 pounds of K per acre and at a slower rate to even higher applications. With 800 pounds of K, exchangeable soil K content was maintained and two‐thirds of the applied K was recovered in the forage. At the 1600‐pound rate, recovery in the forage was reduced but exchangeable soil K content was increased. K content of the forage increased with rates and with yields.
Synopsis
Irrigated, properly fertilized napiergrass, guineagrass and pangolagrass produced 51,491, 41,714, and 18,907 pounds of dry forage per acre yearly, respectively. Yields of napiergrass and guineagrass increased markedly with nitrogen rates up to 800 pounds of N per acre yearly. Protein content of all the grasses increased with nitrogen fertilization up to the 1,600 pound level at which it approached 12% with all species.
An evaluation was made of the changes in soil reaction and exchangeable base content of two Red‐Yellow Podzolic soils and one alluvial soil resulting from high rates of application of ammonium nitrate and of ammonium sulfate.
Severe reductions in exchangeable base level and lowering of soil pH occurred within a year after beginning N applications. The undesirable effects occurred deep in the soil profile where corrections would be difficult, if not impossible, from a practical standpoint. Exchangeable K was lost from the soil faster than other bases at the higher rates of N. No indication of a subsoil zone of accumulation of bases leached out of upper horizons was observed. The measured losses of exchangeable bases were appreciably lower than calculated CaCO3 equivalents of the residual acidity of the fertilizer except for the higher N rates on the Toa clay loam.
Heavily fertilized tropical grasses responded strongly to liming on two typical soils of the Humid Tropics. Liming increased the Ca and decreased the Mn content but did not affect the phosphorus or Mg content of the grasses. Surface applications of limestone were as effective as mixing limestone with the surface soil and one application was as effective as two applications at 2‐year intervals.
Exchangeable Al and Mn content of the soils was sharply increased by fertilization alone but was decreased by liming. Base content at all depths sampled was decreased by fertilization alone but was increased by surface liming followed by heavy fertilization. Yields of grasses increased markedly with pH of the upper 6 inches to about 4.8, with bases to 8.0 me. per 100 g. of soil and with decreasing exchangeable Al to 2 me. per 100 g. of soil.
Heavy fertilization of grasses over a 4‐year period without liming greatly depressed yields of subsequently planted tobacco and this effect was only partly compensated by reliming prior to planting the tobacco.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.