The rural poor of the Yucatán Peninsula, Mexico, rely primarily on shifting cultivation in forested areas to generate income from crop and livestock production. Increased population density has resulted in shortened crop fallow periods, reduced productivity, and consequently increased demand for forest use. The aim of this research was to investigate methods to maintain productivity of cleared crop lands. Manure input from existing sheep and goat farming systems could play a role in reversing the downward spiral in production resulting from shorter fallows. A field experiment was undertaken to examine the effects of three types of weed control (none, hand, chemical), three manure rates (none, 3571 lb DM acre^-1, 7143 lb DM acre^-1), and two plot ages (first year, and second or third year), at two sites. There was a significant (P<0.05) decrease in S, extractable P, Zn, and NH₄ between plot ages at both sites, for soil depth 0-2 in. Extractable P (0-2 in.) declined from 32 ppm for first year plots, to 15 ppm for second year plots. Maize grain yield was significantly higher with manure application, although there were no differences between low and high rates of manure. Maize grain yield was highest with chemical weed control, next highest with hand weed control, and lowest with no weed control. For second and third year plots, grain yield was significantly higher with the low manure/chemical weed control treatment (1716 lb DM acre^-1) than using traditional practices (i.e. no manure and hand weed control, 497 lb DM acre^-1). This suggests that high yields can be obtained in previously used plots with addition of appropriate fertility and weed control inputs. These treatments have potential to sustain the productivity of cleared crop lands, consequently decreasing pressure on remaining forests.