The 4p1000 Initiative: opportunities, limitations and challenges for implementing soil organic carbon sequestration as a sustainable development strategy
Purpose The region of Souss-Massa generates huge quantities of organic horticultural wastes estimated up to 1,307,465 tonsÁyear -1 . Fruit and vegetable producers are asked to process the organic wastes because of the GlobalGAP certification requirements. As a result, there is a need to assess the existing composting plants at regional scale, to improve their efficiency, produce a high-quality soil amendment, free from any pathogens, and weed seeds. Methods The survey consisted of a diagnosis of the quantitative and qualitative status of the organic horticultural wastes (axillary buds; pruned leaves), and an agroenvironmental assessment of nine composting units. Results The analysis of macronutrients (nitrogen, phosphorus, and potassium) in the organic wastes reveals that 13 million euro worth of N, P, and K can be generated by composting all horticultural wastes (12,000 tons of nitrogen, 6000 tons of phosphorus and 14,000 tons of potassium Á year -1 ), constituting for soils an important source of fertilization backup. Results of field investigations showed that 55% of the composting plants have an area equal to one hectare. The proximity between mature piles and raw materials in 55.5% of cases could highly contaminate them by root knot nematode inoculum. Only 11% of composting units were operating on impermeable surface. The test of circular chromatography showed that 80% of sampled composts are immature, even with high operational costs. Conclusion Much effort is required to control and optimize the maturation process. The composting activity should be organized through a professional skilled organization, supported by scientific research and government subsidies.
Dans les périmètres irrigués du Maroc, la pollution nitrique diffuse des eaux souterraines augmente le risque de détérioration de la qualité des ressources hydriques et engendre un risque sanitaire pour la population rurale s'approvisionnant le plus souvent directement de l'aquifère. La présente étude, réalisée dans le périmètre du Tadla (3600 km2), située au centre du Maroc, vise à faire l'état des lieux de la contamination des eaux souterraines par les nitrates et à identifier les causes potentielles de cette pollution. Le suivi de la concentration des eaux souterraines en nitrates a été réalisé durant la période août 1996 - avril 1998 dans un réseau de cent puits. Les paramètres du milieu physique et des pratiques culturales ont été déterminés soit par des mesures au champs, des analyses au laboratoire ou par enquête auprès des agriculteurs dans un réseau de 40 sites. Les résultats sont présentés sous forme de cartes thématiques par le SIG. Le niveau actuel de la pollution nitrique des eaux souterraines dans le périmètre irrigué du Tadla commence à devenir critique. De part la pollution ponctuelle mise en évidence aux alentours de quelques agglomérations urbaines et à l'aval des sucreries, les zones dont les teneurs en nitrates des eaux souterraines dépassent 50 mg NO3- /l sont localisées en aval des Béni Amir et en aval et à l'Est des Béni Moussa Est. Béni Moussa Ouest reste en général moins polluée que Béni Moussa Est. Les apports excessifs en eau et en engrais azotés pour les cultures pratiquées (blé, betterave, cultures maraîchères, arboriculture et luzerne), sont les causes directes de la pollution diffuse. Par ailleurs, il est certain que la texture du sol (argileuse, argilo-limoneuse et limono-argileuse), la teneur en argile (29% à 55%) et tous les paramètres qui leurs sont corrélés notamment la réserve utile du sol, réduisent le risque de lixiviation des nitrates en profondeur et assurent en conséquence un contrôle naturel de la pollution nitrique des eaux souterraines. Néanmoins, tous les autres facteurs étudiés notamment le niveau des nappes faible par rapport au sol (<4m-12m), la vitesse d'infiltration du sol en milieu saturé généralement élevée (20-450 mm/h), les teneurs assez importantes du sol en matière organique (1.5%-3.5%) et en azote total (0.10%-0.15%), joueraient positivement sur la vulnérabilité de la nappe à cette pollution. De même, le pouvoir de minéralisation élevé des sols couplé aux conditions écologiques favorables à une minéralisation intense de la matière organique native du sol, assez caractéristique des régions irriguées à climat méditerranéen, seraient en partie responsable de cette pollution. Néanmoins, Aucune corrélation n'a été mise en évidence entre la teneur en nitrate des eaux souterraines et les combinaisons linéaires des variables du milieu physique. Ceci serait dû à l'homogénéité du milieu physique et à l'accumulation de la pollution suivant le sens d'écoulement des nappes de l'amont vers l'aval hydraulique. Vu le niveau d'intensification agricole que connaît cette région, la situation risquerait de s'aggraver rapidement induisant, en dehors de toute mesure de prévention, la détérioration de la qualité des eaux souterraines dans cette région.
Development of drought‐resistant crops through breeding for extensive root systems emphasizes the importance of subsoil N mineralization for crop production in arid regions. This study was conducted to determine the influence of soil depth on N‐mineralization rate, total N, and amino acid N contents for eight representative soils of the subarid zone of Morocco. Nitrogen‐mineralization ability within the profiles was evaluated through long‐term soil incubation/leaching experiments. Total N and amino acid N were measured by the Kjeldahl method and acid hydrolysis, respectively. A hydrolysable‐N‐production rate was also evaluated, through successive acid hydrolysis of samples from two soil profiles. The changes with depth for the three variables studied were described by two equations. One is a power law of the type Y = AD−B, where Y is one of the variables, A and B are two positive constants, and D is depth. The second is an exponential equation, Y = A exp(−BD). Parameter B had values of 1.3 and 0.04 for N‐mineralization rate, 0.7 and 0.021 for amino acid N, and 0.40 and 0.012 for total N for the power‐law and exponential models, respectively. Significant differences were found between the rates of change with depth (B value) of the three quantities studied using the second equation. The hydrolysable‐N‐production rate decreased with depth in the profiles, indicating a reduction of the chemical degradability of N compounds in deeper horizons. These results suggest that the decrease of N mineralization with depth may be attributed to a recondensation of amino acids in complex biochemical compounds more resistant to biodegradation.
Accumulation of municipal solid wastes, such as household solid waste, can be rated as a harmful, if not critical, pollution problem. However, if these wastes can be composted and the end product used as soil organic amendment or fertilizer, this may represent one of the alternatives for achieving the goal of ensuring integrated and sustainable waste management. The objective of the present work is to evaluate the nitrogen fertilizing value of household solid waste compost in two soils of Morocco with contrasting properties: a sandy soil and a loamyclay soil. The compost used in this study was prepared by aerobic biodegradation using the organic fraction after its separation from the noncompostable materials. A study of nitrogen availability of the compost was carried out in a Soil-Compost-Crop system under greenhouse conditions using lettuce as a test crop. Four increasing compost rates of 0, 10, 20 and 30 tons/ha were applied to the soils. The recommended mineral fertilizer rate by the Agricultural Extension Service for lettuce and its half values constituted additional treatments. The results show a high stock of mineral nitrogen in the loamy-clay soil before crop installation. Unlike the loamy-clay soil, the sandy soil generated a better yield increase and a better response to mineral fertilizers. The effect of compost rate on nitrogen mineralization was significant in the two studied soils. The quantities of mineralized nitrogen of the compost varied between 15 and 24% of the compost total nitrogen applied to the sandy and the loamy-clay soils during the lettuce growing season. Therefore the use of household solid waste compost as soil amendment constitutes a beneficial alternative in Mediterranean soils because it permits the generation of a high nitrogen fertilizing value.
More than 1 million tons of fresh organic wastes is produced in the Souss-Massa region in Morocco. Tomato organic residues represent more than 25% of the total organic wastes and are deposited in uncontrolled landfills. Thus, composting can represent a valuable and pertinent solution to this environmental problem. The objectives of this experiment are to identify the potential functional groups responsible for compost phytotoxicity and to determine the optimum initial carbon to nitrogen ratio (C/N) for maximum recovery of tomato residues. The experiment consisted of the variation of the initial C/N ratios (25, 30, 35, and 40) using mixtures of different raw materials (tomato residues, melon residues, olive mill pomace, and sheep manure). Physicochemical parameters (pH, electrical conductivity, C/N ratio, and humic acid/fulvic acid ratio) were determined and spectroscopic analyses (UV-vis and NMR-C) were performed during the composting process along with quality parameters (germination and phytotoxicity tests) at the end. The results showed that the compost with the initial C/N ratio of 35 is the most humified with the least phytotoxic effect. The germination and phytotoxicity tests were negatively correlated with the methoxyl/N-alkyl-C ratio and O-alkyl-C. These two functional groups are probably the origin of phytotoxicity expression in compost quality tests. Thus, a simple and precise quality test could be performed to evaluate directly the phytotoxicity and maturity of compost.
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