Chemical properties and nutrient and metal availability as consequence of urban waste compost application in soil

Author(s)

Cassio Hamilton Abreu Junior

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 1999-03-31
• Advisor: Takashi Muraoka

Abstract

Two experiments were carried out in green house. In the experiment I, the effects of applying urban waste compost, from S. Paulo city, with or without lime (to reach 70% of base saturation) and fertilizer, on the chemical properties of 21 acid and 5 alkaline soils, and on nutrition and dry matter weight of rice crop were studied. Natural gypsum (3 g dm-3) was applied in the alkaline soil, instead of lime. After incubation for 30 days, the compost (30 g dm-3) and N-P-K fertilizers + micronutrients were applied. The soils were further incubated for 30 days. Then, soil samples were taken for analysis and rice (IAC 165 7 plants per pot), were grown for 60 days. The experimental design was spit-plot completely randomized block with 3 replicates. Rice as then grown again for evaluate the residual effect of compost on the dry matter yield. In the experiment II, the effects of Cd, Cu, Mn, Pb and Zn (0, 15, 30, 60, 120 and 240 mg dm-3) enrichment of compost, on the availability of these metals in the soils, rice plant nutrition and dry matter weight were studied. Seven soils were utilized. The experiment was carried out, as in the experiment I and the experimental design was also similar. The efficiency of extraction methods: Ionic exchange resin, DTPA, Mehlich 1, Mehlich 3, AB-DTP A, Wolf-Morgan, AA-EDTANa2 and CaCl2, in predicting the availability and toxicity of nutrients and heavy metals to rice plants was evaluated. The following elements were determined in both soil and plant samples: P, Ca, Mg, B, Co, Cu, Fe, Mn, Mo, Ni, Zn, Ba, Cd, Cr, Pb, Sr, Ti e V by ICP-AES and K and Na by flame emission photometry. The P, K, Ca and Mg content obtained by resin method and micronutrients and metals obtained by DTPA were considered as the reference for evaluating the chemical properties of soils in the experiment I. The compost application with liming promoted the greater increase on soil pH. The electric conductivity increased around 10 times in the treatments with composts and the effect was the greatest when the compost was applied with fertilizers. The application of compost increased the total N and organic carbon O.M. content, mainly in the sandy and medium texture soil. The Ca and Mg contents were higher and the potential acidity was lower in the treatment compost + liming, while the K content was higher in the treatment compost + fertilizer. The Na content increased due to the compost application, irrespective to lime or fertilizer addition. This increase was proportional to the other exchangeable bases increase. The availability of micronutrients and of heavy metals increased with compost application, being however differentiated as a function of soil texture, native O.M. content and pH, except for V and Ti. The increase on the availability of other metals due to compost did not differ, generally, with the lime and fertilizer application in the acid soils and with gypsum + fertilizer in the alkaline soils. The application of compost + fertilizer, with or without liming, increased the above ground part dry matter weight (AGDMW), in the first and second rice growing, and also of rice roots dry weight (RDW). However, the effects was not better than lime + fertilizer. The application of compost without fertilizers, with or without liming, promoted an intermediate effect, depending on the soil type, but generally superior to the control. In some sandy texture acid soils, hydromorphic or relatively high initial pH soil, the increase on pH, E.C. and exchangeable bases, associated with a probable microbial activity, biochemical transformations and organics/inorganics composts, unusual to the soil caused by the compost application. The dry matter weights were equal or superior to the control treatment. This type of behavior was also, observed in alkaline soils, the saline-sodic soil being outstanding, in which occurred the absence of complete plant development in all treatments. In the second crop, a more uniform pattern was observed among the treatments with compost, and the treatment compost + fertilizer, irrespective to the liming, promoted higher yield of dry matter. These were not significative differences, among the soil chemical properties due to the application of compost enriched with differed metals levels. In the first growing, there were no reduction on AGDMWs up to 30 mg dm-3, except in the PV and LV soils, where the reduction occurred from 60 mg dm-3. The root RDWs, were almost not affected with the metals enrichment up to 60 mg dm-3 and were less affected, also, in the PV and LV soils. The capability of PV and LV soils on promoting greater AGDMW and RDW, under high metals doses (over 30 mg dm-3 metals), may be related to high native O.M. content (41 and 31 g dm-3, respectively) present in these soils. In the second growing, there was decrease of approximately 25 to 40% in AGDMW in the 0 to 15 mg dm-3 compost metal enrichment. This difference between the crops might be caused, probably, by the soil pH reduction, due to subsequent fertilizer applications, mainly with nitrogen (urea), and to the crop itself, increasing the solubility of O.M. bound metals, CEC and Fe and Al oxides, which passed to toxic levels. (AU)