This study was carried out during seasons 2018/2019, and 2019/2020, in Tayba Block-the Sudan - Gezira central clay plains, to evaluate the field performance of four land preparation methods using three tillage equipment: chisel plow "intensive tillage", disc harrow "medium tillage", ridger "minimum or reduced tillage" and no tillage machine. An overall tilth index to reflect field performance of tillage methods was determined from four measured soil tilth indicators (bulk density, porosity, aggregate uniformity, and penetration resistance). Diagnosis of land preparation methods was made using analytical hierarchy procedure (AHP) for ranking tilth indicators by weight assignment and determination of overall tilth index using a linear relation. The results show that Bulk density of the soil surface layer was reduced by tillage implements compared to no till. High significant difference at 1 % level was observed between reduced or no tillage and intensive tillage by chisel or disc harrow on average percentage Soil porosity. Bulk density and Soil porosity are inter-related with similar trend. Aggregate stability showed highest value with no till treatment followed by chisel plow, while those obtained by harrow or ridger implements do not differ significantly. Penetration resistance was significantly lowered by tillage implement compared with using no tillage machine. The highest reduction is achieved by disc harrow followed by ridger and the least reduction is made by chisel plow. Penetration resistance is interrelated to Bulk density. Using analytical hierarchy procedure ranked the tillage indicators in descending order by weight values of 1.01, 0.62, 0.29 and 0.12 for Penetration resistance, Bulk density, Porosity, and Aggregate particle stability respectively. The diagnosis of tillage alternatives by development of the overall tillage index resulted in ranking tillage methods in descending order of preference as: ridger, disc harrow, chisel plow, and no tillage machine. It is thus recommended to use reduced tillage "ridging only" as the most technically feasible tillage method achieve an optimal seedbed with minimum energy input.
ABSTRACT Determination of reference evapotranspiration (ETo) in required for design, management and scheduling of irrigation water in fan and pad greenhouses. In actual practice estimation of (ETo) in fan and pad greenhouses is often made using the Penman-Monteith FAO-56-PM; method from external meteorological data. This requires availability of accurate meteorological input data (temperature, relative humidity, wind speed, and solar radiation). This is constrained by lack of such data which is a common problem in developing countries. In this study the proposed procedure to estimate ETo is based on using limited data of outdoor historically recorded climate elements of only temperature wind speed, and site characteristics (altitude, latitude and sun shine hours). In the proposed method radiation is to be predicted from data of air temperature difference rather than its direct measurement. This because radiation measurement using pyranometers and net radiometers is borne to errors calibration errors commonly plagued by hysteresis, and nonlinearity. The obtained results of the proposed alternative procedure were statistically validated in comparison with the standard method (FAO 56 PM) using unlimited input data measured inside the greenhouse and in reference to a directly measured ETo values by class-A-evaporation pan. The performance of the developed model was evaluated by the determination coefficient of the regression "R2 for goodness-of-fit" and by using the Root Mean Square Error (RMSE). The needed data is collected during three years in three sites in Khartoum North-Sudan El Alafoon, Halfaya, and Shambat. In each site three greenhouses were employed, and data is taken every three days for three months in each year. The obtained result reveals that the proposed limited data procedure to estimate the ETo inside greenhouses agree on statistical basis well with both pan measurement and PM estimation from measured indoor climate variables. The study reveals importance of temperature data for estimating ETo in greenhouses and calls for insuring high quality temperature data for calculating ETo in fan and pad greenhouses.
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