Effects of Residue Management and Cropping Systems on Wheat Yield Stability in a Semiarid Mediterranean Clay Soil

Agriculture is the single biggest user of land and water in Morocco;however its performances are still low due to high rainfall variation and rates of soil productivity depletion. Increasing concerns about soil and environment quality degradation have raised the need to review existing tillage management systems and develop new systems for seed-bed preparation. Consequently, No-tillage is found a promising practice of soil management to improve simultaneously soil quality and wheat production in semiarid Morocco. However, residue management under No-tillage was Not yet studied in conjunction with wheat rotation. Therefore, a field study was conducted in the semiarid Chaouia Plain of Morocco during the period from 1994 to 2003, in order to evaluate the impacts of different tillage practices (conventional tillage (CT), No-tillage (NT));No-tillage wheat residue management scenarios (total NTr, partial NTp and No-removal of residues NTm) and crop rotations (continuous wheat (CW), Wheat-Fallow (WF), Wheat-Maize-Fallow (WMF), Wheat-Lentil-Fallow (WLF) and Wheat-Barley-Fallow (WBF)) on wheat production. Over-years, conventional tillage system permitted lower yield of wheat while NT maintenance of crop residue at the surface is needed to increase it. Basically, NTp could be adopted in mixed crop-livestock systems of semiarid areas for the purpose of guarantying grain and feed. Wheat yields were the lowest under continuous wheat for all years. Wheat-fallow rotation is an important option in dry years or areas, while wheat-fallow-lentil or barley rotations are recommended in better environments. Stability analysis indicated that yields in the No-tillage system were less influenced by adverse growing conditions than conventional tillage system, particularly under low rainfall. These results indicate that improved soil quality under No-tillage enhanced wheat yield stability by reducing the impact of adverse growing conditions.

Use of a calibrated SWAT model to evaluate the effects of agricultural BMPs on sediments of the Kalaya river basin (North of Morocco)

Soil erosion from agricultural fields is a worldwide problem,to influence water quality,soil fertility and reservoir sedimentation especially in Mediterranean countries such as Morocco.In fact,this work assesses the effects of Best Management Practices (BMPs) on sediments using the Soil and Water Assessment Tool (SWAT) model in the Kalaya watershed in Northem Morocco,to recommend the most appropriate practice.This study is based on the use of three most usable practices:contouring,stripcropping and terracing,by the calibrated SWAT model.The general parameters of the model have been modified to reflect the implementation of different agricultural BMPs used.Resulting sediment yield were compared with the baseline scenario,for validation.However,the effective measures to reduce sediment losses at the watershed level are organized according to their effectiveness,and these are terracing (28% reduction and the value is 15t/ha/yr) followed by strip-cropping (9% reduction and the value is 5t/ha/yr).In contrast,measurements performed by the contouring are inappropriate for the study area because they have contributed to increasing the soil erosion (more than 31% of losses and the value is 17t/ha/yr more than existing conditions).Therefore,the model illustrates that the terrace is effective for reducing sediment losses and limiting soil erosion especially on steep slopes.Thus,the results provide useful information for targeted management in order to implement the most effective agricultural BMPs in the watershed.

Assessing sediment yield in Kalaya gauged watershed(Northern Morocco)using GIS and SWAT model

An efficient design for erosion-control structures of any watershed in the world is entrusted with the delicate forecasting of sediment yields.These outlook yields are usually inferred by extrapolations from past observations.Because runoff,as the transporting vehicle,is more closely correlated with sediment yields than any other variable.So,calibration as well as validation of process-based hydrological models are two major processes while estimating the sediment yield in watershed.The actual survey is fulfilled with the aim of developing a trustworthy hydrologic model simulating stream flow discharge and sediment concentration with least uncertainty among the parameters picked out for calibration so as to verify the effect of the scenarios on the spatial distribution of sediment yield(sediments transported from sub-basins to the main channel during the step of time).Soil and Water Assessment Tool(SWAT,version 2012)model integrated with Geographic Information System(GIS,version 10.1)was used to simulate the stream flow and sediment concentration of Kalaya catchment situated in north of Morocco for the period from 1971 to 1993.Model calibration and validation were performed for monthly time periods using Sequential Uncertainty Fitting 2(SUFI-2,version 2)within SWAT-CUP using 16 parameters.Our calibration outputs for monthly simulation for the period from 1976 to 1984 showed a good model performance for flow rates with NSE and PBIAS values of 0.76 and
11.80,respectively;also a good model performance for sediment concentration with NSE and PBIAS values of 0.69 and 7.12,respectively.Nonetheless,during validation period(1985–1993)for monthly time step,the NSE and PBIAS values were 0.67 and
14.44,respectively for flow rates and these statistical values were 0.70 and 15.51,respectively for sediment concentration;which also means a good model performance for both.Following calibration,the inclusive effect of each parameter used was ranked using global sensitivity function in SWAT-CUP.From our analysis,the effective hydraulic conductivity in main channel alluvium(CH_K2),USLE support practice factor(USLE_P)and manning's"n"value for the main channel(CH_N2)were found to be the most sensitive parameters during different iterations with different number of simulation but with the same inputs.The least sensitive parameter were found to be different in either cases unlike the most sensitive parameters.As a result,the global evaluated soil erosion rate in the study area varied from 20 to 120 t/ha/yr.It was summarized that the entire knowledge of the hydrologic processes happens within the watershed and the consciousness about acceptable meaningful range of the parameters is crucial while developing reliable hydrologic model.

Soil erodibility mapping using three approaches in the Tangiers province–Northern Morocco

Soil erodibility is a key factor in assessing soil loss rates.In fact,soil loss is the most occurring land degradation form in Morocco,affecting rural and urban vulnerable areas.This work deals with large scale mapping of soil erodibility using three mapping approaches:(i)the CORINE approach developed for Europe by the JRC;(ii)the UNEP/FAO approach developed within the frame of the United Nations Environmental Program for the Mediterranean area;(iii)the Universal Soil Loss Equation(USLE)K factor.Our study zone is the province of Tangiers,North-West of Morocco.For each approach,we mapped and analyzed different erodibility factors in terms of parent material,topography and soil attributes.The thematic maps were then integrated using a Geographic Information System to elaborate a soil erodibility map for each of the three approaches.Finally,the validity of each approach was checked in the field,focusing on highly eroded areas,by confronting the estimated soil erodibility and the erosion state as observed in the field.We used three statistical indicators for validation:overall accuracy,weighted Kappa factor and omission/commission errors.We found that the UNEP/FAO approach,based principally on lithofacies and topography as mapping inputs,is the most adapted for the case of our study zone,followed by the CORINE approach.The USLE K factor underestimated the soil erodibility,especially for highly eroded areas.