Agronomic evaluation of Leucaena.: Part 1.: Adaptation to environmental challenges in multi-environment trials

A multi-environment trial was conducted to evaluate the performance of high yielding accessions from most taxa of Leucaena, for broad and specific adaptation to growth-limiting environments, and to develop an understanding of environmental parameters limiting growth of this important multipurpose tropical tree-legume genus. Eighteen sites were selected to include environments known to constrain the growth of L. leucocephala. Accessions were planted in replicated line plots, with 10 trees/plot, spaced 50 cm apart, and with rows spaced 3 m apart. Environmental parameters measured were maximum and minimum temperatures, rainfall and psyllid pressure. Soil fertility and acidity indices were derived from soil analyses. A KX2 F1 hybrid accession proved broadly adapted with high yield rankings in all environments, and with yield advantage greatest at low temperature and high psyllid pressure sites. Specific adaptation to low temperature environments was identified in L. trichandra OFI53/88, and to a lesser extent in L. pallida CQ3439. No accessions were specifically adapted to acid-infertile soils. Highest dry matter production was achieved in fertile, hot, humid, low psyllid environments. Very low growth rates were achieved in acid-infertile and low temperature environments. Yield was strongly reduced by mean monthly minimum temperatures of <22 degrees C, mean monthly maximum temperatures of <29 degreesC, psyllid pressure of >2.5 (1-9 scale of increasing pressure based on damage to young leaves), acidity index of <6 (1-7 scale of decreasing acidity based on soil pH and Al saturation) and fertility index of <9 (1-12 scale of increasing fertility based on critical soil nutrient levels).