Watercourse Improvement in Pakistan

Extensive conveyance loss measurements in watercourses in the Pakistan Indus Basin indicated water loss in the range of 30 to 50 per cent of the inflow. This high loss motivated the development and testing of several system improvements which could be grouped in the categories of improved maintenance, redesign and earthen reconstruction, and channel lining. Evaluation of the costs and water savings of these techniques allowed the formulation of an optimal watercourse improvement strategy. This improvement strategy, which increases water deliveries to the field by 30 per cent, is presently being applied on a large scale by the Pakistan On-Farm Water Management Project. Total farmer provision of labor is evidence of their support for the program and recognition of its benefits

Interpretation of SoilData from the Rain Project

Process-oriented models for prediction of soil and water acidification at the catchment scale require soil chemical and physical data as input parameters. Choice of soil properties characteristic for an entire catchment poses a major dilemma. This report deals with the interpretation of analyses from about 200 soils samples collected 1983-86 from the 7 catchments included in the RAIN project (Reversing Acidification In Norway). Various statistical techniques are used to derive characteristic values for key soil parameters such as cation exchange capacity, base saturation, bulk density, and anion absorptionMiljøverndepartemente

Critical loads for soils in Norway. Preliminary assessment based on data from 9 calibrated catchments

Critical load for acid deposition with respect to soils are calculated for 9 calibrated catchments in southern Norway. Two methods recommended by the UN-ECE Handbook on Mapping Critical Loads were used: The stratic empirical model, and the dynamic MAGIC model. The critical load for soils follow two criteria: runoff water must have alkalinity > 0 (fish criterion), and the Al/Ca equivalent ratio in soil solution < 1.5 (forest criterion). The results show that for these Norwegian sites with thin and patchy soils, the fish criterion is always the more strigent. Further work should evaluate regional soils data and assess the future role of nitrogen.Norwegian Directorate for Nature Management (DN

The seasonal variation in soil water acid neutralizing capacity in peaty podzols in mid-Wales

Between 1985 and 1990, bulk precipitation and soil solution from the organic (Oh) and mineral (Bs) horizons of a well developed podzol were regularly sampled at a moorland catchment in Mid-Wales. Samples were analysed for pH, major cations, major anions, and dissolved organic carbon (DOC). Acid neutralizing capacity (ANC) was estimated by the charge balance method. Average monthly ANC of soil solutions from the Oh horizon varied seasonally, with a maximum in July and a minimum in February. In contrast, H+ concentrations varied little. Solute deposition, dominated by sodium and chloride, also varied seasonally with a winter maximum, which is reflected in the soil solution chemical composition. In the Oh horizon during winter, the increase in base cation (Na) concentrations led to release of H+ through ion exchange. ANC declined in the absence of any buffering mechanism. In summer, the depletion of exchangeable acidity that occurred in winter, was replenished by H+ produced by the dissociation of organic acids. During this period, organic anions contribute to an increase in ANC, while H+ concentrations remained similar to those in winter. These processes probably influenced the acidity and ANC of Bs horizon soil solutions but to a lesser extent than in the Oh horizon. Other mechanisms such as weathering and ion exchange involving H+ and Al may buffer solution acidity in the mineral soil

Distribution of cadmium in a cultivated soil in Britanny, France Distribuição de cádmio em solo cultivado na Bretanha, França

Cadmium (Cd) can be potentially toxic to the environment, and its bioavailability is related to the chemical forms it occurs in the soils. The distribution of Cd into the solid phase and its availability was investigated in a cultivated soil in Britanny, France. Cd sequential extraction was performed using a modified Tessier's sequential extraction protocol. Total content of Cd (n = 22 samples) ranged from 0.13 to 0.37 mg kg¹. Long term history of organic and mineral fertilizers application increased Cd concentration in the surface horizon. The fate of Cd was correlated with soil available P2O5 concentration and pH. The regression analysis (linear and non-linear) and Principal Component Analysis revealed the synergistic effect of P2O5 in the retention of Cd in cultivated soils. The following fractions' sequence was observed: bounded to Fe and Al oxides + phosphates > exchangeable > bound to organic matter » residual fraction.<br>O cádmio (Cd) pode ser tóxico no ambiente e sua biodisponibilidade está relacionada às formas químicas em que os metais se encontram no solo. Apresenta-se a distribuição deste metal na fase sólida de um solo cultivado na Bretanha, França, assim como fatores que influenciam sua disponibilidade. Foi realizada a extração sequencial do Cd utilizando o método Tessier, modificado. A concentração total de Cd, avaliada em 22 amostras, variou de 0,13 a 0,37 mg kg¹. O uso contínuo de fertilizantes orgânicos e minerais aumentou a concentração de Cd no horizonte superficial do solo. A distribuição do Cd foi relacionada à concentração de P2O5 disponível e ao pH. Análises de regressão (linear e não linear) e a Análise de Componentes Principais mostraram efeito sinérgico do P2O5 na retenção de Cd nos solos cultivados. O fracionamento apresentou a seguinte sequência: ligado a óxidos de Fe e de Al + fosfatos > trocável > ligado à matéria orgânica » residual