The variability of level and sloping terraces in eastern Nepal and the implications for the design of experiments

Nepalese hillside terraces are classified into two broad groups, sloping or bari terraces which are only rainfed, and level or khet terraces which are commonly flood irrigated but may also be rainfed. Although such terraces m ay be adjacent, the process of irrigation by flooding and puddling changes the pattern of variability both within and between terraces. Data collected from Pakhribas Agricultural Centre, Dhankuta, Nepal, were used to describe this variability. The variability is manifest not only in the soil charact eristics of the two terrace types, with khet terraces being more uniform th an bari terraces both within and between terraces, but also in the variabil ity of field experiments on the two terrace types. However, both terrace ty pes exhibit similar patterns of variability which influence the design of e xperiments. These include the following: a gradient between the terrace ris er and wall which is generally more important than gradients along the terr ace, variability within terraces which can preclude the assumption that plo ts on the same terrace are similar, and variability between terraces which requires experimental units in the same block to be assigned to the same te rrace.