Soil fertility diagnosis of coffee farms

The first two principal components account for 76% of the total variance (Table 4). The first component has the higher explanatory power of the data. In this component, positive values for soil pH, EC, exchangeable bases, ECEC, Ca/Mg, Mg/K, OM and total N (group 1) are observed more or less in similar proportions; other variables such as Na saturation percentage, Al saturation percentage, Fe, Mn, Zn and P are grouped in opposing areas of the former group. There is a high correlation between the components and variables, which assures the representativeness of the variables. The magnitude of the values is associated with desirable and un-desirable soil characteristics. As these properties are linked to the concept of nutrient availability, high values in the variables of the first group are linked to adequate soil fertility. The second component explains 14.0% of the total variability. If this component is associated with the first, it may indicate that the soils have adequate acidity, Na saturation percentage, Al saturation percentage and Cu and a few have problems of acidity or salinity (Table 4).

The analysis discriminates two different site-categories as opposite positions (Figure 1). On the left figure shows, related to CP1, sites with content items associated with soil salinity and acidity levels, including Monteada Nueva, La Lanza, Bahoruco, La Cienega, Los Patos and Platon. Items associated with fertility rates differ on the right vertical axis given by CP1, which relate to locations such as Breton, Los Charquitos, Maria Teresa, El Pino, Santa Elena, Chene and Las Guazaras. In the upper quadrants, with respect to CP2, there are areas with the highest correlation elements to this component and lower quadrants elements with negative relationship.

In the cluster analysis, the locations El Pino, Chene, Maria Teresa, Los Leonardos, Breton, Santa Elena and Las Guazaras are grouped together (Figure 2). This differentiation is shown with a dotted vertical line drawn from a value representing 50%o of the maximum average euclidean distance (DEPmax), according with Indeangelo et al (2007). The locations Las Lanzas, Polo and Los Charquitos are grouped as sites having a soil pH pattern that is different than the other localities, forming the classes A, C and D, respectively. Los Patos, Platon, Monteada Nueva, La Cienaga and Bahoruco are located in class B and are characterized as having a moderately to strongly acid soil pH.