A low-input cropping system has been developed at Yurimiaguas, Peru, to serve as a transition technology between shifting and continuous cultivation for acid soiln of the humid tropics. Principal features are slash-andburn clearing, rotation of acid-tolerant upland rice and cowpea cultivars, maximum residue return, no tillage, and no lime or fertilizer apoiications. When yields decline as a res...

The aim of the study was to document wheat landraces that were and and Dandi districts, West Shewa, Ethiopia; and to investigate the extent of genetic loss and its causes. Survey was carried out in three Peasant Associations of Ambo District and four Peasant Associations of Dandi District from 2007 to 2008. Three to five farmers’ group per Peasant Association containing 5 to 12 individual farme...

Recently, quantile regression (QR) models are often applied for longitudinal data analysis. When the distribution of responses seems to be skew and asymmetric due to outliers and heavy-tails, QR models may work suitably. In this paper, a semi-parametric quantile regression model is developed for analysing continuous longitudinal responses. The error term's distribution is assumed to be Asymmetr...

Due to lack of using pesticides in production of green leaf, Iran’s produced tea is considered as of the purest and healthiest teas in the world [1]. Although, by passing one century from commencement of tea cultivation and production in Iran, tea cultivation surfaces has been developed and numbers of tea making factories has been increased, no progress has been made in improvement of quality o...

We study the convex hull of the feasible set of the semi-continuous knapsack problem, in which the variables belong to the union of two intervals. Besides being important in its own right, the semi-continuous knapsack problem arises in a number of other contexts, e.g. it is a relaxation of general mixed-integer programming. We show how strong inequalities valid for the semi-continuous knapsack ...

Semi-continuous data arise in many applications where naturally-continuous data become contaminated by the data generating mechanism. The resulting data contain several values that are “too frequent”, and in that sense are a hybrid between discrete and continuous data. The main problem is that standard statistical methods, which are geared towards continuous or discrete data, cannot be applied ...