Back A. D. Paschoal1, S. K. Homma2, A. B. Sanches2 and M. C. S. Nogueira1
Luiz de Queiroz, College of Agriculture, University of Sao Paulo, Piracicaba, SP, Brazil1 and
Mokich Okada Foundation, Ipeuna, SP, Brazil2
Full Paper (PDF File: 282KB)
Abstract
A field investigation was conducted during 1993-94 on citrus in the State of Sao Paulo, Brazil, to evaluate the interactions of EM with soil, leaves, mite populations, fruit quality and yield of orange trees. The study was designed to test the ability of Effective Microorganisms (EM) to significantly change a number of soil parameters in the citrus agroecosystem. Climate of the site is a CWa type. The predominant soil is a Typic Hapludox, a well-drained clay soil with high hydrogen and aluminum content, low base saturation, and a moderate organic matter content. The sweet orange trees were the Pera variety (Citrus sinensis Osbeck) grafted to Cravo lemon rootstock (Citrus limonia Osbeck). The experimental design was a randomized complete block design (RCBD), with four replicates for each of the following treatments: 1) Control (C); 2) EM applied to soil (EMS); 3) EM applied to citrus trees (EMP); and 4) EM applied to soil and to citrus trees (EMPS). The EM culture used in the experiment was a modified mixture of the three basic cultures and was applied at monthly intervals.
Analyses of soil chemical properties showed: 1) a highly significant increase in the soil organic matter content due to EM, especially in the fall season; 2) a highly significant increase in soil pH due to EM in the fall of 1993 which tended to decline in the summer of 1994; 3) a significant increase in the levels of some soil macronutrients due to EM, including Ca, Mg and K; 4) a highly significant increase in soil cation exchange capacity (CEC) due to EM, especially in the fall of 1993; 5) a significantly lower soil base saturation for the EMS and EMP treatments, probably due to the high levels of H+ and Al+3 ions; and 6) no significant differences in the levels of soil P and micronutrients due to EM treatment.
There were no significant differences in soil physical properties between EM treatments and the control. However, soil penetration resistance to an impact penetrometer tended to be less in the EM-treated plots than the controls. There were no significant differences in the nutrient content of citrus leaves for EM treatments and the controls. An exception was Zn which was lower at times for the EMS, EMP and EMPS treatments compared with the control.
Populations of the citrus rust mite (Phyllocoptruta oleivora Ashmead) on green fruits were higher for the EMP and EMPS treatments compared with the control and EMS. Foliar-applied EM increased the rust mite populations while soil-applied EM decreased their numbers. Consequently, farmers are advised to cease foliar application of EM and use only soil-applied EM when rust mite populations are highest, i.e., from February to May.
Yields of oranges harvested in late August 1994, after 18 EM applications, were significantly higher in the EMS and EMPS plots. The higher yields can be correlated with improved soil chemical and physical conditions. Fruit quality analyses indicated a significant increase in juice content from the EM treatments and fruit peels were thinner due to EM compared with the control.