A THESIS SUBMITTED IN FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY OF SOKOINE UNIVERSITY OF AGRICULTURE, MOROGORO, TANZANIA. 2016The study on which this thesis is based investigated the impact of land size and farm fragmentation on household welfare in Kilosa District. The specific objectives were to: determine factors affecting household land size, assess the effects of farm size on household income, determine the causes of farm fragmentation, and assess the effect of farm fragmentation on agricultural productivity. Data were collected using a structured questionnaire, which was administered to a random sample of household heads in the study area. The area was demarcated into three strata, namely improved irrigation system, traditional irrigation system and no irrigation practice at all. Statistical Package for Social Sciences (SPSS) and Microsoft Excel programmes were used to analyse the data after ensuring that there was no violation of assumptions of normality, linearity, homoscedasticity and heterogeneity. It was found that land access, size and fragmentation do negatively affect the household income which eventually affects household welfare. It was found that owned land size is a function of adult equivalent unit (p < 0.05), age of household head (p < 0.05) and household income (p < 0.05). Farm fragmentation was statistically described to be a function of average travel time from homestead to the farm (p < 0.01), total land owned per capita (p < 0.01), number of crops grown by household (p < 0.05), total arable land per capita (p < 0.05) and means of land acquisition (p < 0.05). Agricultural productivity decreased with farm fragmentation hence the Schultz’s theory which asserts an inverse relationship between farm fragmentation and agricultural productivity was disproved. Land consolidation and installation of modern irrigation structures are therefore recommended for improved productivity, increased income and enhancement of welfare of farmers in the study area.