Impact of Plant Covers on Nutrient Losses by Agricultural Runoff from the Taluses of Terraces with Subtropical Crops
Non-point source pollution is a serious problem that degrades surface waters and aquatic ecosystems. Loading of nutrients, sediment, and other pollutants from the agricultural runoff may compromise the integrity of freshwaters. In particular, in the coast of Granada (SE Spain), an intensive irrigated agriculture has established subtropical crops including avocado (Persea americana Mill.), mango (Mangifera indica L.), loquat (Eriobotrya japonica L.), cherimoya (Annona cherimola Mill.), litchi (Litchi chinensis Sonn.) and others. However, these crops have been planted on terraces, which are usually damaged by aggressive rainfall events, characterized by irregular distribution in space and time, with extreme values. Moreover, when agricultural plants replace native vegetation, the natural cycle is altered, and nutrients can be readily transported by runoff and sediments. The conventional agriculture requires substantial fertilization, often applying more nutrients than required by crops. Such excesses imply environmental pollution both from runoff and sediment during rainfall events. In this study, we monitored the transport of nutrients in runoff from terraces to evaluate the effectiveness of protecting terrace slopes by using covers of plants which have multiple uses (aromatic, medicinal, culinary and mellipherous). For this purpose, we installed eight erosion plots were located on the taluses of the terrace (214% slope), at 180 m in altitude and with 16 m2 (4 m ×4 m) in area. Three plant covers were tested, and twice replicated: Thymus mastichina (TM), Lavandula dentata (LD) and native spontaneous vegetation (NSV), and bare soil (BS) without plant cover as a control. Runoff rates, as well as the nutrient fluxes of nitrate, ammonium, phosphorus and potassium by runoff were evaluated during two years. Annual runoff rates for NSV, LD, TM, and BS were of 10.4, 13.3, 14.3, and 29.8 mm yr-1, respectively. The NSV registered the lowest total PO4 3- losses, reducing with respect to remaining treatments (0.4, 0.7, 1.4, 0.7 and 2.1 mg m-2 yr-1 for NSV, LD, TM and BS, respectively). The lowest rate for K losses was found from LD plot (79.2, 88.6, 107.9, and 219.6 mg m-2 yr-1, for LD, NSV, TM, and BS, respectively). Similar trend was recorded for LD in reducing the NO3-losses from the taluses of orchard terraces (92.5, 140.1, 146.8, and 158.6 mg m-2 yr-1, for LD, TM, NSV, and BS, respectively). In relation to the ammonium losses lowest rate was found for the NVS plot (4.3, 6.9, 8.8, and 30.1 mg m-2 yr-1, for NSV, LD, TM, and BS, respectively). The concentrations of NO3-and PO4 3- exceeded in some events the tolerable concentration limits for drinking water and protection of freshwater against eutrophication, mainly in BS. The results of this study showed the importance of the plant covers in controlling the pollution risk from conventional agriculture in orchard terraces in a fragile Mediterranean agroecosystem especially those plants with potential multiple uses.
nitrate non-point pollution runoff terrace protection
Carmen Rocio RODRíGUEZ PLEGUEZUELO Víctor Hugo DURáN ZUAZO Francisco José MARTíN PEINADO Dionisio FRANCO TARIFA
IFAPA Centro Camino de Purchil. Apdo. 2027,18080 Granada,Spain Departamento de Edafología y Química Agrícola,Universidad de Granada,C/ Severo Ochoa s/n,18071-Grana Finca El Zahori. Patronato de Cultivos Subtropicales Plaza de la Constitucion 1,Almu(ne)car (Grana
国际会议
2009 International Symposium on Environmental Science and Technology(2009环境科学与技术国际会议)
上海
英文
339-342
2009-06-02（万方平台首次上网日期，不代表论文的发表时间）