The effects of sewage sludge compost applications on a Mollisol and an Ultisol of Puerto Rico were evaluated. Experimental rates were control (0 compost), 37, 74, and 148 t/ha/yr, which were to be applied during a three year period. In addition, a treatment consisting of a single application of 445 t/ha was included to assess the impact of single massive applications vs. continuous applications of compost. Results here presented pertain exclusively to the project's first year. The compost was obtained from the sewage sludge compost facility of Puerto Rico's Solid Waste Management Authority in Arecibo. The material was predominantly inorganic and exhibited a high soluble salt content, which diminished its quality. Compost additions caused significant pH increases in both soils. The effects were more noticeable on the Ultisol (Corozal clay), where pH increased from 4.55 in the control to 6.45 with the lowest compost treatment. The electrical conductivity of both soils increased considerably with compost additions, sometimes approaching limits considered detrimental to support crop growth. The organic matter content of both soils also increased with compost additions. This increase had a positive effect on their water retention capacity. Nitrogen contributions from the compost were minimal. However, significant increases in the levels of phosphorus were observed in both soils. Compost additions caused significant increases in the levels of EDTA extractable metals (i.e., Cu, Zn, Cd, Cr, Fe). However, elements regulated by the U.S. Environmental Protection Agency (e.g., Cd, Pb, Cr) were added in amounts well below the established limits, and thus were not a reason for concern.
In Puerto Rico yam (Dioscorea spp.) is usually planted in thoroughly tilled soils of the mountain region. An experiment was established in an Ultisol (aquic tropudults), a Vertisol (udic chromusterts) and an Oxisol tropeptic haplorthox) to study the effect of tillage and fertilizer rates on yield of the Binugas yam (Dioscorea alata L.). Three tillage treatments (conventional, deep and minimum) were compared to no-till; and three fertilizer levels (0, 1X and 2X the recommended level) were evaluated. The highest yields were observed in the conventionally tilled plots but differences among tillage treatments were significant only in the Ultisol and Vertisol soils. At these sites, yields under no-tillage were significantly lower than those under conventional tillage. No yield response to tillage was observed in the Oxisol, possibly because of the good physical condition of this soil. Response to fertilizer treatments was observed only in the Oxisol, a soil of low native fertility.
Two trials were carried out during 1986-87 at the Corozal substation to evaluate six herbicides for weed control in yam. In the first test, herbicides evaluated were ametryn, fluazifop-P, oxyfluorfen and paraquat. Ametryn at 4.48 kg ai/ha, in sequential application with fluazifop-P at 0.56 kg ai/ha, was highly effective against broadleaf weeds. Oxyfluorfen alone and oxyfluorfen + paraquat were also highly effective, but both treatments caused slight to moderate crop injury. In the second trial, ametryn, fluazifop-P, paraquat, cinmethylin and metolachor were evaluated. Ametryn at 4.48 kg ai/ha in sequential application with fluazifop at 0.84 kg ai/ha again proved to be highly effective. Cinmethylin alone was poor against broadleaf weeds. Its sequential application with paraquat slightly improved weed control. Metolachor at 3.54 and 7.08 L/ha+ paraquat also provided good weed control. Its sequential application with paraquat slightly improved weed control. Metolachor at 3.54 and 7.08 L/ha + paraquat also provided good weed control. In the first planting there were no significant differences in tuber yield between the weeded check and other herbicide treatments except for the fluazifop-P alone treatments. In the second planting, with the exception of the cinmethylin alone treatments and one of the cinmethylin + paraquat treatments, there were no significant yield differences between the weeded check and the herbicide treatments.
RESPONSE OF CABBAGE IN THE MOUNTAINOUS AND COASTAL AREAS OF PUERTO RICO
COMPORTAMIENTO DE PATRONES EN COMBINACIÓN CON TANGELO ORLANDO
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