The aim of this research is to develop an analytical methodology for the determination of complexed element in fertilizers and, then, to obtain an adequate criteria for the inclusion of these products in European Regulations on Fertilizers. This paper compares the CEN method EN 13366:2001, based on the retention of the cations into a sulfonated resin, and an AOAC modified method, based on the precipitation of the inorganic forms at pH 9. A limited interlaboratory trial was carried out to demonstrate the applicability of the AOAC modified method and to study the effect of the removal of organic compounds and the addition of a matrix modifier solution before the element quantification. Then, a global interlaboratory trial was developed to evaluate the validation and quality parameters of the method. As a second objective, the AOAC modified method was applied to the determination of the complexing capacity of complexing agents based on lignosulfonates and amino acids. The AOAC modified method was the choice methodology because it is adequate for the determination of complexing capacity of micronutrients in fertilizer.
Cropping systems that fail to manage N and irrigation, with the objective of reducing losses of N, are frequently associated with elevated concentrations of nitrate N in soil and ground water. A long‐term (4‐yr) field experiment was carried out at La Poveda Field Station (30 km southeast of Madrid, Spain) with the objective of assessing whether the effect of traditional cultivation practices (irrigation and fertilization) can be reduced. The experiment was conducted on a Typic Xerofluvent soil and a crop sequence (corn‐wheat‐corn‐oat) traditional in the area. Four fertilizer treatments (unfertilized check, urea, floranid [a slow‐release N fertilizer] and municipal organic waste [MOW] compost) were combined with two irrigation schedules (traditional and improved) in two sets of 24 plots. Seasonal drainage was estimated by the zero flux plane‐water balance equation and nitrate concentration was measured at the soil depth of deep percolation (1.4 m) by ceramic cup extraction system. Nitrate leaching could be attributed to both irrigation schedule and fertilizer type. Within fertilizer treatments, reductions of nitrate losses between irrigation schedules of 52, 51, 66, and 81% were found for the unfertilized check, urea, floranid, and MOW compost, respectively. Grain yields in the whole crop sequence were not affected by fertilizer or irrigation managements.
Lignin was used as a majority component in a controlled-release fertilizar coating, since this waste product displays properties that make it an ideal substance for application in soil together with conventional mineral fertilizers. Pine lignin marketed under the ñame of Indulin AT and obtained by the Kraft process was used. Insoluble in water for all pH valúes that may occur in soil, this product was employed for coating pelleted urea. Seven series of fertilizar were obtained, which also contained various types of rosins and in some cases linseed oil as additives. The physical-chemical evaluation of these fertilizers showed that the most efficient are those whose coating embodies a mixture of dimerized, esterified, and natural rosins, as well as lignin. It was also demonstrated that the efficiency of the producís noticeably increases by adding linseed oil as a sealing agent.
The agronomic and ecotoxicological effects of the application of pig (Sus scrofa) slurry during a maize (Zea mays L.) crop cycle under conditions of forced irrigation were evaluated. The 0.2-ha experimental area, of typical xerofluvent soil and of known vulnerability to nitrate (NO3-) contamination, was divided into 12 plots and provided with water measurement instruments (TDR-probes, vertical tensiometers, and ceramic candles). Samples of soil, water, soil organisms, and the crop were subjected to analytical, agronomic, and biological test procedures. The following fertilizer treatments were applied to triplicate plots: urea (U;170 kg N ha(-1)), and an optimized (P1; 162 kg N ha(-1)) and triple (P3; 486 kg N ha(-1)) dose of pig slurry. Unfertilized plots (P0) served as controls. Calculation was made of seasonal drainage and leached NO3- and sodium losses during the experimental period. Conductivity, heavy metal concentration, hardness, pH, and redox potential were determined in soil solutions. The ecotoxicological evaluation of the soil solution and matrix was based on ecotoxicity bioassays and the quantification of organic and inorganic compounds [phenols, indols, polychlorinated biphenyls (PCBs)]. The results suggest that the P3 treatment is highly contaminating due to the leaching of nitrates and increased soil salinity. Despite the fact that a Folsomia candida reproduction test indicated chronic ecotoxicological effects on the soil in plots treated with P1 and P3, the absence of organic compounds suggests that these effects may be attributable to contaminants not considered in this study.
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