CP Phase III Final Report 1991_Part 2.pdf - Lee Daniels - Soil and ...

II. MINE SOIL FERTILITY AND PLANT NUTRITIONStanding Biomass ProductionAll rock mix plots received an initial N-P-K fertilization in spring1982 and annual additions of 56 Kgfha N in fall 1982, 1983, 1984 , and 1985to simulate the N that would be added by a vigorous legume component.Standing biomass production in the rock mix experiment shows the effect ofthese annual N additions . Yields on the rock mix plots were higher in 1982and 1983 (Table 15).Although yields in 1984·, 1986, and 1987 were lower,the rock mix plots outperformed the control, topsoil , sawdust, and 22Mgfha sludge plots of the surface amendment experiment during these years,apparently because the N reservoir established by the annual N additionswas still active. In 1989, however, rock mix experiment yields were muchlower than in 1987, and were similar to the yields on the control plots ofthe surface amendment experiment.Mixtures containing a high proportion of sandstone initiallyoutyielded pure siltstone spoils, but by 1984, yields on all rock mixplots were not significantly different. In some cases, mixtures thatinitially produced the highest yields had the lowest yields in followingyears .High standing biomass production stimulated by N additions mayhave tied up avail able N in litter so that it was not available for plantnutrition in subsequent years.In 1989, all the rock mixtures had similaryields .The control, topsoil, and sawdust plots of the surface amendmentexperiment received an initial N-P-K fertilization, with sawdust plotsreceiving an additional amendment of slow-release N to compensate for38