Ingrid Walter

Plant and Soil Responses to the Application of Composted MSW in a Degraded, Semiarid Shrubland in Central Spain

Composted municipal solid waste (MSW) was assessed as a soil amendment material for restoring the canopy cover of a degraded soil in an area with a Mediterranean climate. Four rates (0, 40, 80 or 120 Mg ha−1) of MSW were surface-applied to a calcareous soil in central Spain and the effects on soil properties and the native plant community recorded over the next five years. Soil N, P and K levels increased significantly after application. Soil organic carbon (OC) increased with the amount of MSW applied, but the differences were small and inconsistent. Soil total Zn, Pb, Ni and Cu increased in the MSW-treated soils compared to the controls, but levels were still below the maximum allowed by Spanish legislation. DTPA-extractable soil Zn and Cu were the only heavy metals studied that increased with MSW application, but their concentrations were still adequate for plant growth. Total aerial plant biomass yields and canopy cover increased with MSW amendment compared to the control treatment. Plant production increased three fold in the amended plots in the first years and than declined with time, although no consistent trends were observed. The percentage canopy cover ranged from approximately 82 to 100 % in the MSW treatments and from 43 to 49% in the control throughout the study period. Native plant species richness decreased slightly with increasing MSW rates. Differences in the plant communities developing on the control and MSW-treated plots were observed, with a reduction in perennial species and an increase in annual species after five years. Plant tissue N, P, K, Zn and Cu levels generally increased with the MSW rate. Thus, MSW application have a positive effect on the soil chemical characteristics and on the native vegetation without causing environmental damage. MSW may therefore be of use in the rehabilitation of ecosystems similar to that studied.

Composted MSW Effects on Soil Properties and Native Vegetation in a Degraded Semiarid Shrubland

Three rates of dried composted MSW (40, 80 and 120 Mg ha−1) were surface applied to a degraded semiarid shrubland site near Madrid in central Spain. Various soil and plant parameters were determined one year after its application. MSW amendment had an effect on soil chemistry and nutrient levels. Available P and K, concentration of N-NO3 and EC. increased significantly after the MSW application. The concentration of total soil heavy metals, Zn, Pb, Cd, Ni, Cr and Cu rose with the application of MSW as compared with the control plot, but these increases were only significant in total Zn, Pb and Cu. Zn and Cu amounts of DTPA-extractable soil were also significantly higher in the amended soil. Total plant cover increased significantly in the plots treated with low and intermediate MSW rates. Total biomass production increased as compost rates were added but this rise is not proportional to the amount of MSW added. The degraded soil used in this study may require MSW rates up to 80 Mg ha−1 to improve soil chemical properties as well as to produce minimal changes in the native vegetation.

Nitrogen Mineralization and Released Nutrients in a Volcanic Soil Amended with Poultry Litter

Optimum application rates of poultry litter (PL) spread out on the farmers field is a valuable source of available plant nutrients. The aim of this study was to compare the effect of two rates of PL and conventional fertilization (CF) on N mineralization and P, K, Zn, and Cu availability in an Andisol from Southern Chile under controlled conditions. Aerobic incubation was carried out for a 16-wk period. N mineralization rates were higher (61.5%) with the two PL treatments than with conventional fertilizer (23%). CF was associated with high N availability prior to the start of incubation and slight immobilization during the first week, perhaps due to a more rapid conversion of urea into NH4 which was then temporarily immobilized by the microbial biomass. At the start and end of the incubation period, Olsen-extractable P content was generally higher in CF. Due to the high fixation capacity of the soil studied, extractable P values were slightly increased suggesting that PL mineralization is only associated with a low risk of P contamination in volcanic soil. In PL, K, Zn, and Cu availability were higher than in CF. However, values obtained for Cu and Zn were average in relation to referential values used in agricultural soil. The results indicated that PL could be an alternative to conventional fertilizer under the conditions of the present study.

Carbon Dioxide Flux in a Soil Treated with Biosolids Under Semiarid Conditions

The restoration of degraded land using biosolids provides a well known means of recycling these organic residues. In semiarid ecosystems they can enhance the chemical and physical properties of the soil and stimulate soil microbe growth and activity, leading to increases in soil fertility and quality. However, the respiratory activity in biosolids-treated soil may contribute to an increase in atmospheric CO2. Few studies examining CO2 emissions from biosolids-amended soils in semiarid climates have been conducted under field conditions. The aims of the present study were to determine the effect of applying different amounts of biosolids on the soil organic matter content and respiratory activity of a semiarid, abandoned agricultural soil. The CO2 fluxed from the soil surface (kg CO2 ha−1 d−1) was measured using a portable analyser. Soil temperature and soil water content were measured in the first 5 cm of soil. The results show that a large proportion of the organic matter incorporated into the soil via the biosolids was easily biodegradable in the first three years following its application. In addition, biosolids application generally increased soil CO2 emissions, although in a manner not proportional to the quantity applied. Differences in soil humidity were associated with differences in soil CO2 flux over the year. The soil water content was the major factor affecting soil respiration; a strong correlation was found between these variables. Soil respiration activity could serve as a useful index of soil biological activity, allowing the decomposition of biosolids under field conditions to be monitored.

Short-Term Effects of Poultry Litter Application On Silage Maize Yield and Soil Chemical Properties

If properly managed, poultry litter (PL) might be a good alternative to conventional fertilizers. This paper reports on a three-year field study to compare the effects of two consecutive PL and traditional mineral fertilizer applications on silage maize (Zea mays) production and soil chemical properties. The experiment was undertaken on volcanic soil in the Central-South Region of Chile. The PL was applied at doses of 10, 15 and 20 Mg ha−1, with and without mineral fertilizer to 50 m2 plots, and the outcomes compared with those obtained with two rates of nitrogen mineral fertilizer equivalent to the mid and high PL rates. Maize yield showed a positive response to all treatments, although the mean yield obtained with the PL treatments was higher than with the mineral fertilizer in the third year, in which no fertilizers were applied. The whole plant N concentration of the PL plants was significantly higher than that of the plants that received mineral fertilizer (this was the only nutrient variable for which such differences were found), but the values were not related to the amount of PL applied. After two annual applications of PL, slight increases in soil-available inorganic N and P were observed. However, the values obtained were low, highlighting the high P fixation capacity of the soil as well as its high capacity to stabilise organic matter. No other soil variables studied were significantly affected by any of the treatments.

Biomass Production and Development of Native Vegetation Following Biowaste Amendment of a Degraded, Semi-Arid Soil

Water erosion is a worrying environmental problem affecting many Mediterranean soils, which are subject to progressive degradation due mainly to the loss of organic matter. To promote the restoration of an abandoned, degraded soil with a semi-arid climate, sewage sludge (SS) and municipal solid waste (MSW) were surface-applied once only to field plots with an 8–12% slope at four different rates: 0, 40, 80, 120 Mg ha−1. The growth of native plants was enhanced by the addition of these organic wastes. Total plant biomass and canopy cover increased significantly and remained higher in all the biowaste treatments over the 5-year study period. An estimated maximum biomass of 550 g m−2 was obtained when 80 Mg ha−1 of SS were applied; for MSW, a maximum estimated value of 361 g m−2 was obtained with the 40 Mg ha−1 rate. Native plant species richness decreased with an increasing biowaste application rate. Differences in the composition of native plant communities were observed among treatments, but with a reduction in perennial and an increase in annual plants seen in all biowaste-treated plots. This was more remarkable in the plots in which SS was applied, and was seen throughout 5 years of the study. Increasing biowaste rates resulted in somewhat increased nutrient concentrations, mainly nitrogen; this effect was less evident in the last years. All plant heavy metal concentrations determined were below those considered hazardous.

Effect of soil cadmium concentration on three Chilean durum wheat cultivars in four environments

ABSTRACT Durum wheat (Triticum turgidum L. var durum) is a species that accumulates cadmium (Cd). Durum wheat cultivars differ in their absorption ability of Cd; therefore, identifying and selecting genetic material with low Cd accumulation reduces human exposure to this toxic element. In the present study, Cd concentration was evaluated in three Chilean durum wheat cultivars (Llareta-INIA, Corcolén-INIA, and Lleuque-INIA) grown in four Chilean locations with varying concentrations of Cd in soils. The objective of this study was to evaluate the response of these durum wheat cultivars to different doses of cadmium in terms of grain yield; Cd concentration in different plant tissues (grain, straw, roots); soil Cd concentration was also evaluated. Results show that grain yield was not affected by soil Cd; differences in Cd concentration in plant tissues were generally associated with location, cultivar, and soil Cd concentration. Grain Cd concentration in all three cultivars was classified in the low accumulation category for this metal; ‘Lleuque-INIA’ noted as having a very low accumulation.

Cadmium phytoextraction capacity of white lupine (Lupinus albus L.) and narrow-leafed lupine (Lupinus angustifolius L.) in three contrasting agroclimatic conditions of Chile

The phytoextraction process implies the use of plants to promote the elimination of metal contaminants in the soil. In fact, metal-accumulating plants are planted or transplanted in metal-contaminated soil and cultivated in accordance with established agricultural practices. The objective of the present study was to evaluate the productivity and Cd phytoextraction capacity of white lupine (Lupinus albus L.) and narrow-leafed lupine (Lupinus angustifolius L.), as well as the effect on residual Cd concentration in the soil. Both species of lupines were grown at three CdCl2 rates (0, 1, and 2 mg kg-1), under three agroclimatic conditions in Chile in 2013. In the arid zone (Pan de Azucar, 73 mm precipitation), narrow-leafed lupine production was significantly (P < 0.05) higher than white lupine (4.55 vs. 3.26 Mg DM ha-1, respectively). In locations with higher precipitation (Santa Rosa, 670 mm; Carillanca, 880 mm), narrow-leafed lupine DM production was slightly higher than in Pan de Azucar, but white lupine was approximately three times higher. Total plant Cd concentrations in white and narrow-leafed lupine increased as Cd rates increased in the three environments, but they were much higher in narrow-leafed lupine than white lupine; 150%, 58%, and 344% higher in Pan de Azucar, Santa Rosa, and Carillanca, respectively. Cadmium uptake (g Cd ha-1) and apparent recovery were also higher (P < 0.05) in narrow-leafed lupine in two environments (Pan de Azucar and Carillanca). These results suggest that narrow-leafed lupine present higher potential as phytoremediation species than white lupine.

Restoration of Abandoned, Degraded Agricultural Soil Using Composted Biosolid: Influence on Selected Soil Properties

One practice for reclaiming degraded agricultural soils under semiarid climate is to use organic amendment to improve the physical, chemical, and biological properties of the soil, therefore enhancing its fertility. A short-term field experiment was carried out to study the effects of different biosolid rates on selected soil properties and assess these as potential indicators of soil restoration. The organic waste was surface-applied once at three rates (30, 60, and 90 Mg ha−1) to an abandoned agricultural soil. Three years after the biosolid was applied several chemical and biological soil properties such as organic C (SOC), humified C fractions (THS-C), water soluble C (DOC), total nitrogen (Nk), basal respiration (CO2-E), and potential nitrogen mineralization (PMN) increased significantly in 60 Mg ha−1 and in 90 Mg ha−1 biosolid rates. The physical soil properties studied did not change with the biosolid treatments at least in this short-term experiment. The available heavy metals showed a slight increase in the biosolid treatments but the values obtained were below those considered phytotoxic. In spite of that the canopy cover was higher in the biosolid treatment plots than in the unamended soil which will contribute to soil restoration; the analysis of the biological properties did not show such a clear trend that they could be used as soil quality indicator under the condition of this study.

Bioabsorption and Bioaccumulation of Cadmium in the Straw and Grain of Maize (Zea mays L.) in Growing Soils Contaminated with Cadmium in Different Environment

There is a worldwide increase of heavy metal or potentially toxic element (PTE), contamination in agricultural soils caused mainly by human and industrial action, which leads to food contamination in crops such as in maize. Cadmium (Cd) is a PTE often found in soils and it is ingested through food. It is necessary to determine the bioabsorption, distribution, and accumulation levels in maize to reduce or prevent food chain contamination. Cadmium absorption and accumulation in three maize cultivars were evaluated in three agricultural environments in Chile by increasing CdCl2 rates (0, 1, and 2 mg·kg−1). Evaluation included Cd accumulation and distribution in different plant tissues, bioaccumulation factor (BAF), bioconcentration factor (BCF), translocation factor (TF), and tolerance index (TI). Cadmium whole-plant uptake was only affected by the CdCl2 rate; the highest uptake was obtained with 2 mg·kg−1 CdCl2 (34.4 g·ha−1) (p < 0.05). Cadmium distribution in the maize plant usually exhibited the highest accumulation in the straw (p < 0.05), independently of the environment, Cd rate, and evaluated cultivar. Given the results for TF (TF > 2) and BAF (BAF > 1), the Los Tilos and Chillán environments were classified as having a high capacity to contaminate the food chain for all evaluated cultivars.