International Journal of Environmental & Agriculture Research (IJOEAR) ISSN:[2454-1850] [Vol-5, Issue-4, April- 2019] Page | 19 Different land use systems improve soil fertility status of sandy soil and increase the yield of rice under rain-fed wet lowland tropical climatic conditions in Papua New Guinea James Aipaa 1 , Patrick S. Michael 2 1 University of Natural Resources and Environment, Private Mail Bag, Kokopo, East New Britain Province, Papua New Guinea 2 Department of Agriculture, PNG University of Technology, Lae, MP 411, Papua New Guinea. Abstract— The pratical use of different land use systems(LUS) as a management strategy and the effect of the LUSon soil proprties as an indicator of soil fertility status, and the understanding of the long-term effect of the LUS, are important to maintaining optimal soil fertility and yeild of crops. In the rain-fed wet lowlandtropical soils, studies related to rice production and the associated effectson soil properties are limited to a few studies. In this study, we investigated the effects of four LUS (crop rotation, continuous cropping, manure application and fallow) on soil properties that influence soil fertility status and yield of crops under a rain-fed wet lowland tropical sandy soil conditions.The data were compared with the natural soil data obtained prior to and at the end of the study. All the LUS had no to small effects on bulk density, moisture content, electrical conductivity and pH.Soil organic carbon, total nitrogen, available phosphorus, extractable potassium, and cation exchange capacity were all higher in all the LUS.Crop rotation increased soil organic carbon and cation exchange capacity, fallow increased total nitrogen, and manure application increased available phosphorus and extractable potassium contents, respectively.The LUS had no significant effects on particle composition except that small increases in the silt contentswere observed in the continuous, rotation and fallow systems. In almost all cases, soil organic carbon content influenced the fertility status of the sandy soil and yield of rice. Higher soil organic carbon contentresulted in higher available phosphorous and extarvale potassium,enhence reulted in higher yield of rice but decreased the total nitrogen content.Our results implied that the soil organic carbon content of sandy soils needs to be managed properly for optimal soil fertility and higher yieid. Keywords— land use systems, soil fertility, yield of rice, rain-fed, sandy soil. I. INTRODUCTION In agriculture, a good soil in terms of fertility is a soil which is able to deliver to the roots of crops nutrients that are needed for optimum growth and development. A fertile soil required for crop production is an attribute of the biophysical and biochemical composition of the soil [1; 2; 3]. Some of the important physical components of soils are particle size distribution, bulk density, field capacity, and soil color, whereas the chemical components include pH, electrical conductivity, organic matter, cation exchange capacity (CEC), and carbon to nitrogen (C: N) ratio. The third component of the soil system is the biological component, mostly all the living things. The physical, chemical and biological components of the soil affect several processes important to crop production[4]. For instance, particle size distribution affects infiltration rate and CEC[5], soil pH and redox affect soil nutrient status and availability to crop plants[6; 7; 8].The biological component provides important ecological services in evolution of soil fertility and management of problem soils through decomposition of organic matter [9].In agricultural crop production, it is important properties are managed as their interactions that govern nutrient and availability to crops are affected by on the farm soil use systems [10] and affect farmers who depend on them [11; 12; 13]. The LUS is affected by the economic status of the farming community, the type of crop produced and thelevel of production. Farmers in the developed nations are able to afford farm machineries and farming technologies for intensive crop production. In the poor economies, affordability of farming equipment is a major concern, complicated by lack of investment and technical knowledge to intensify crop production. Regardless of where and how crop is produced, the increase in the human population and too many mouths to feed worldwide means more and more farm land and continuous crop production. In the tropics, continuous farming is solely monocropping of stables; sweet potato (Ipomoea batatas), taro (Colocasiaesculenta), cassava (Manihotesculenta) and yam (Discorea sp.)in the tropical and rice (Oryzasativum),maize (Zea mays) and wheat (Triticumassertivum) in the temperate regions are dominating the farms.