Irrigation return flows and phosphorus transport in the Middle Ebro River Valley (Spain)

Currently, there is an increased interest in the study of phosphorus (P) loss from soils aimed to understand and mitigate water eutrophication problems. The main objective of this study is to describe P losses in five irrigated agricultural watersheds considered as representative in terms of agricultural water management. Weekly water samples were collected during the 2007 hydrologic year (HY) at the watershed outlets and three P forms (total P, TP; total dissolved P, TDP; and particulate P, PP) were analyzed during irrigation (IS) and non-irrigation season (NIS). The P load per hectare was used to compare the study areas with other non-irrigated agricultural watersheds in Spain and Europe. Results indicate that most of the study areas showed increases in TP at higher flows. Annual TP concentrations were higher than the critical eutrophication threshold (0.02 mg L�1), with TDP being the dominant fraction. The TP was higher during the IS than during the NIS, except for the Arba River where seasonal TP concentration showed the highest values (0.237 and 0.275 mg L�1, respectively). Results also show that average TP yield (0.73 kg P ha�1 year�1) was higher than others reported on non-irrigated agricultural lands in Spain and Europe. This work is of great relevance and indispensable for guiding future research on P transfer aimed at establishing corrective measures to sustain irrigated agricultural productivity and surface water quality

Simulation of sprinkler irrigation water uniformity impact on corn yield

In a previous work, the spatial and temporal wind effects on corn yield were analysed using Ador-Crop (based onthe FAO crop model CropWat) and a solid set sprinkler irrigation model. The combined model could explain only 25% of the variability of measured yield. The objective of this work was to evaluate the predictive capacity of two more advanced crop models (EPICphase and DSSAT) when coupled to the solid set sprinkler irrigation model. EPICphase explained 44% of total dry mater (TDM) and grain yield (GY) variability when measured irrigation was used. The combination of EPICphase and the solid set sprinkler irrigation model explained better the variability of TDM than that of GY (42% and 35%, respectively), although the error in the estimation of GY with the coupled model was higher than when measured irrigation doses were considered (1.55 t ha the FAO crop model CropWat) and a solid set sprinkler irrigation model. The combined model could explain only 25% of the variability of measured yield. The objective of this work was to evaluate the predictive capacity of two more advanced crop models (EPICphase and DSSAT) when coupled to the solid set sprinkler irrigation model. EPICphase explained 44% of total dry mater (TDM) and grain yield (GY) variability when measured irrigation was used. The combination of EPICphase and the solid set sprinkler irrigation model explained better the variability of TDM than that of GY (42% and 35%, respectively), although the error in the estimation of GY with the coupled model was higher than when measured irrigation doses were considered (1.55 t ha the FAO crop model CropWat) and a solid set sprinkler irrigation model. The combined model could explain only 25% of the variability of measured yield. The objective of this work was to evaluate the predictive capacity of two more advanced crop models (EPICphase and DSSAT) when coupled to the solid set sprinkler irrigation model. EPICphase explained 44% of total dry mater (TDM) and grain yield (GY) variability when measured irrigation was used. The combination of EPICphase and the solid set sprinkler irrigation model explained better the variability of TDM than that of GY (42% and 35%, respectively), although the error in the estimation of GY with the coupled model was higher than when measured irrigation doses were considered (1.55 t ha�1 vs. 1.22 t ha�1). The DSSAT model explained 39% and 38% of the variability in TDM and GY, respectively, when measured irrigation data was used. When DSSAT was considered in the coupled model, better results were obtained for TDM (R2 = 41%) than GY (R2 = 31%). The EPICphase model simulated grain yield more accurately than the DSSAT model because it produced a better prediction of the maximum LAI. The combination of the sprinkler irrigation model with the EPICphase or DSSAT models simulated crop growth and yield more accurately than when combined with the Ador-Crop model

Water quality: 13. Phosphorus

Phosphorus (P) is an important nutrient for plant and animal growth. However, additions of P to the land as livestock manure and inorganic fertilizer may lead to an increased risk of soil P saturation and resulting movement of P to water bodies. Excessive amounts of P in surface water contributes to eutrophication of rivers and lakes and to Cyanobacteria blooms. These result in decreased water quality and limitations on water use. The Risk of Water Contamination by Phosphorus (IROWC-P) Indicator was developed to assess the trends over time for the risk of surface water contamination by P from Canadian agricultural land at the watershed scale. Overall risk of water contamination by P is increasing in Canada. Increases in livestock production and the use of mineral fertilizers repeatedly created regional P surpluses between 1981 and 2006. The wide range of soil types across Canada have different characteristics for retaining nutrients such as P and therefore some soils are better able than others to sustain intensive agriculture. Surface runoff, deep drainage and soil erosion by water on agricultural land contribute significantly to the risk of P contamination of surface water in eastern Canada. In western Canada, surface runoff seems to be the major factor contributing to P transport. Local implementation of nutrient management plans, regulations, conservation practices and beneficial management practices (BMPs) have considerably decreased the P surplus in some areas. However, cumulative P surpluses over time continue to enrich soil P levels. Increased efforts at controlling both P sources and transport are required to reduce the risk of P loss to water and prevent surface water eutrophication and algal blooms