Roughness Coefficient of Micro-irrigation Laterals

A micro-irrigation system' must apply water and fertilizer uniformly over the entire field. However friction loss in pipes and fittings, and differences in elevation cause water pressure to vary. Discharge variations due to pressure differences and manufacturing variations cause non-uniformity of irrigation. To assure maximum economy, the hydraulic design of the system must be adequately evaluated for the required level of uniformity. This paper presents results of laboratory tests for head loss in smooth polyethylene pipe fitted with insert emitters. The Hazen-Williams roughness coefficients are included in the friction factor-Reynolds number diagrams so that system designers may choose a more accurate friction coefficient to improve energy, water and material use efficiency of a micro-irrigation system

Hydraulic Analysis of Micro-irrigation Laterals: a New Approach

The current approach in hydraulic analysis of micro-irrigation laterals has been derived from sprinkler irrigation design where pipe sizes and flow rates are large. The approach assumes uniform emitter discharge and emitter barb head loss, or uses empirical formula which are not applicable to micro-irrigation systems due to errors caused by ignoring the effect of water temperature. The formula do not fit the actual head loss in small diameter polyethylene pipes for the range of Reynolds number normally encountered in micro-irrigation and should not be used for accurate analysis. The Darcy-Weisbach equation with a combined friction factor for the smooth pipe and local loss due to emitter connection used in a step by step evaluation of head loss gives more accurate results than the current method. The new approach also considers emitter manufacturing variation, and the effect of temperature changes on emitter discharge and lateral flow rates. This approach makes the use of equivalent pipe length for emitter connection head loss and a factor for dividing flow unnecessary

Evaluation of SPAD Chlorophyll Meter in Two Different Rice Growth Stages and its Temporal Variability

Recently, agriculture production systems have benefited from incorporation of technological advances primarily developed for other industries. Site-specific crop management, well-established in some developed countries, is now being considered in other places such as Malaysia. The application of site-specific management principles and techniques to diverse crops and small-scale farming systems in Malaysia will present new challenges. Describing within-field variability in typical Malaysian production settings is a fundamental first step toward determining the size of management zones and the interrelationships between limiting factors, for establishment of site-specific management strategies. Measurements of rice (Oryza Sativa L.) SPAD readings was obtained in a Malaysian rice paddy field those were manually collected on 2 different rice growth stages(55 DAT and 80 DAT) and measured using a Minolta SPAD 502. Analysis of variance, variogram and kriging were conducted to determine the variability of the measured parameter. Finally, SPAD reading maps were created on the interpretation of the data was investigated

Impact of water resources availability on agricultural sustainability in the Gavkhuni river basin, Iran

One of the most interesting water management case studies in Iran is the case of Zayandehrud River, the main river that supplies water to Isfahan Province which is located in Gavkhuni River Basin (GRB). This paper examines the present and future demands for water and determines the extent to which water will be available for agricultural use by the year 2020. Although demand and supply conditions in 2000 were more or less in balance, there was an increase in the supply of some 28% by 2010 due to the completion of the third trans-basin diversion and the development of other local water sources. However, the demand exceeded its supply in 2010 and the basin fell into severe deficit. In this condition, the only way to keep supply and demand in balance is to reduce allocations to agriculture. By 2020, agriculture would only have 5% more water than the present and water supply is only 90% that of the normal, and this would then shrink from 2025 onwards. In other words, agriculture would have to be sacrificed in order to ensure full supplies of water for the other sectors. The scenarios examined reveal that a sustainable agriculture can only be accomplished by water saving practices and management measures, which may further lead to reduced demand, control supplies, and improve the efficiency of water use

Development of on-the-go soil nitrogen mapping system for site specific management

Site specific management can potentially improve both economic and ecological outcomes in agriculture. Effective site specific management requires strong and temporally consistent relationship among identified management zones; underlying soil physical, chemical and biological parameters, and crop yield. Those requirements are possible to be obtained through the use of specific equipment and state-of-the art technology. This study was carried out to develop an on-the-go system to provide accurate soil nitrogen map by using an electrical conductivity sensor. The result from this study has proven the merit of the developed system in terms of its performance and its reliability. The soil nitrogen map produced via this system was almost similar to a kriging map produced via ArcGIS software and it was shown to be reliable for use in the site specific application for best management practices. This finding shows that the soil nutrient variability map was possible to be produced in real-time basis without engaging any tedious work in the field. The use of this mapping system as a basis of identifying the soil nutrient variability proved to be a good technique for the farmers to better manage their paddy fields

A review of optical methods for assessing nitrogen contents during rice growth

Concerns over the use of nitrogen have been increasing due to the high cost of fertilizers and environmental pollution caused by excess nitrogen applications in paddy fields. Several methods are available to assess the amount of nitrogen in crops. However, they are either expensive, time consuming, inaccurate, and/or require specialists to operate the tools. Researchers have recently suggested remote sensing of chlorophyll content in crop canopies as a low-cost alternative to determine plant nitrogen status. This article describes the most recent technologies and the suitability of different remote sensing platforms for determining the status of chlorophyll content and nitrogen in crops. Finally, the role of vegetation indices in nutrient assessment is explained. Among different remote sensing platforms, a low altitude remote sensing system using digital cameras, which record data in visible bands can be used to determine the status of nitrogen and chlorophyll content. However, the vegetation indices need to be correctly chosen for best results

Evaluation of bioengineering soil erosion control techniques in standard usle plots

An erosion control study on Serdang series soil was conducted in standard USLE plots at DBAE Field Station, UPM. The bioengineering erosion control techniques include vetiver (Vetiveria zizanioides), legume (Arachis pintoi), spot turfing and close turfing with cowgrass (Axonopus compressus), hydroseeding and few combinations of hydroseeding with biomats. A plot was left bare as a control. Close turfing gave better soil protection than the other grass species, reducing soil loss by 99% compared to the bare plot. The addition of "fibromat" to the hydroseeding plot resulted in significantly lower soil loss. All hydroseeding plots overlaid with biomats gave better protection, resulting in C factor lower than 0.004. Close turfing produced C factor of 0.004, compared to 0.017 for spot turfing, 0.021 for hydroseeding only, 0.122 for vetiver and 0.213 for legume. From statistical correlation results, soil loss from the bare plot was better correlated with KE>25 than raindepth, EI30 and AIm