A greenhouse study was conducted to evaluate the effect on total growth and leaf nutritional content in lettuce (Lactuca sativa L.) in the Agrotechnology Sciences Department of the Universidad Autonoma de Chihuahua, Mexico in 2007. Three types of fertilization treatments were analyzed: two organic and one conventional or inorganic. Both vermicompost and compost were produced from cattle manure in a 25-wk process. The study included 12 experimental units made up of lettuce plantlets var. Great Lakes. A linear model was fitted for statistical analysis using a completely randomized experimental design. ANOVA was performed and means were compared by orthogonal contrasts. Results showed differences in weight and leaf content for the N and K variables, and the highest mean values for these variables were in the urea treatment. Leaf content of Ca, Mg, and Mn showed higher values in organic fertilization treatments. The vermicompost treatment showed a higher contribution of Mg, Fe, Zn, and Cu, and lower Na in lettuce leaf content when compared to compost usage.

The efficiency of composting processes with and without the addition of Californian red worms (Eisenia foetida) was evaluated, using manure of dairy cows to generate organic fertilizer. Several parameters were assessed as physiochemical indicators of maturity, such as temperature, pH, C/N ratio, phytotoxicity and macro and micronutrients at 25 and 54 wk (mature and stored products, respectively). A linear model was used in the statistical analysis, with four replicates that included as fixed effects, the composting systems and time. At 25 wk, both systems reduced the C/N ratio to values of 15.5 in vermicompost and 17.1 in semi-compost. The content of total N, N-NO3, Ca and some micronutrients also increased. K and Na concentrations were higher in the compost than in the vermicompost. The mean of pH presented differences in the two systems of decomposition. The germination index, using lettuce seeds (Lactuca sativa L.) var. Grandes Lagos in vitro, of the decomposition products increased in week 25, indicating the degree of maturity reached. The effect of storage was greater stability of the products by reducing the C/N ratio to 8.13 for vermicompost and 7.05 for compost, as well as an increase in available N content in the form of N-NO3 in the case of compost and in the content of Ca, Mg, Na, Zn, Mn and Cu in both systems.

Three Candida oleophila strains (L06, L07 smooth, and L07 rough) were evaluated in vivo and in vitro as biocontrol agents against Penicillium expansum on postharvest 'Golden Delicious' apples (Malus domestica Borkh.) in Chihuahua, Mexico. The in vivo and in vitro activity of exo-β-1,3-glucanase was measured as a possible biocontrol mode of action for C. oleophila. Mean disease incidence caused by P. expansum was 0.3% for apples treated with fludioxonil + ciprodinil, which were used as a positive control, and 1% for fruits treated with a combination of the three C. oleophila strains; the effects of these treatments were significantly equivalent. Disease incidence in control apples was 39% and was significantly different from the other treatments. The in vivo exo-β-1,3-glucanase activity began at 24 h and peaked at 72 and 96 h for all treatments. Strain L06 had the highest activity (7.96 nKat) and a specific activity of 2.92 nKat μg -1 . Candida albicans had the lowest activity (2.83 nKat) and a specific activity of 0.67 nKat μg -1 . The highest in vitro activity was for C. albicans (85.03 nKat) and the lowest for strain L06 (78.2 nKat). Significant differences in both in vivo and in vitro enzymatic activity were observed between strain L06 and C. albicans. Polynomial regression analysis (R 2 = 0.96 in vitro and 0.68 in vivo) indicated that increased enzymatic activity was associated with reduced fruit disease incidence. The production of exo-β-1,3-glucanase by C. oleophila is a possible mode of action for the efficient biocontrol of P. expansum on postharvest apples.