Years Of Amendment Research Articles

Soil fertility and plant nutrition in an organic olive orchard after 5 years of amendment with compost, biochar or their blend

The agronomic use of compost and biochar as soil amendments may exhibit contrasting results in terms of soil fertility and plant nutrition. The effects of the biennial application of biochar, compost and a blend of compost:biochar (90:10; % dw:dw) on the agronomical performance of an organically managed and well established 25-year-old olive orchard was assessed 5 years after the initial application. The agronomical evaluation was based on the assessment of the soil physical, chemical, and biological characteristics, and the assessment of the soil fertility by both crop production and nutritional status of the orchard, and the bioassay with olive plantlets. Biochar mainly benefited the physical properties (bulk density, total porosity, aeration, water retention capacity) of soil, especially in the top 0–5 cm. Compost and its blend with biochar improved microbial activity, soil nutritional status (increasing the content of soluble organic C, N, and P) and favoured the formation of aggregates in soil. The bioassay conducted with young plantlets confirmed the enhanced soil fertility status in the three amended treatments, particularly in the case of biochar and its blend with compost. However, this effect was not significantly observed in the adult plants after 5 years of application, reflecting the slow response of adult olive trees to changes in fertilization. Based on these results, alongside the desirable long-residence time of biochar in soil and the ready availability of compost, the blend of biochar with compost assayed in this study is defined as a valid strategy for preparing high quality soil organic amendments.

Soil physical properties of a Luvisol developed on loess after 15 years of amendment with compost

Recycling composted organic residues in agriculture can reduce the need for mineral fertilizers and improve the physicochemical and biological properties of cultivated soils. However, more studies dealing with soil physical properties after compost amendment are still needed. The objective of this study was to investigate the impact of long-term compost amendment on soil physical properties in a silt loam Luvisol under a maize-wheat rotation in the Paris Basin. Since 1998, three composts and one manure were applied every second year after wheat harvest, at a rate of ca. 4 Mg C ha−1. Bulk density, organic carbon concentration on a mass basis, water holding capacity, gas transport properties and Atterberg limits were measured on topsoil samples taken 15 years after the beginning of the experiment. Soil moisture was monitored in the field down to a depth of 160 cm during two years with different climatic conditions: a year with a dry summer (2010) and a year with a wet summer (2012). Compost and manure amendments reduced bulk density and increased organic carbon concentrations, which improved apparent air permeability and gas diffusivity, but only one of the amendments (a green waste-sewage sludge compost) increased water-holding capacity. The amendments also increased the water contents at the Atterberg limits and overall produced better soil conditions for tillage and other agricultural operations, in particular in wet years. However, field moisture measurements showed that in general, soil water contents were not higher in the amended soils than in the control at any of the periods considered.

Long Term Amendment with Fresh and Composted Solid Olive Mill Waste on Olive Grove Affects Carbon Sequestration by Prunings, Fruits, and Soil.

The soil amendment with organic wastes represents a way to increase the soil fertility and the organic carbon (C) stored in the agro-ecosystems. Among the organic waste materials produced by agricultural and industrial activities, olive mill wastes derived from the olive oil extraction process may represent a suitable soil amendment. The aim of the study was to evaluate the effect of fresh (SOMW) or composted mixture of SOMW and shredded olive tree prunings (C-SOMW+P) on the vegetative and productive activities of olive trees, on the C stored in the tree non-permanent structures (prunings and fruits) and in the soil. The plots treated with SOMW or C-SOMW+P showed higher vegetative and productive activities than the untreated plots, and this was attributed to the higher total N and availability of P and K supplied by the amendments. Consequently, treatments increased the C sequestered in the tree non-permanent structures than in the control trees. However, no significant different effect between SOMW and C-SOMW+P treatments was found for the C stored in prunings and fruits, whereas it was evident a stronger influence of C-SOMW+P than SOMW on soil C sequestration. Indeed, about 50% the C supplied by the treatment with C-SOMW+P was sequestered in the olive grove system, with more than 90% of the sequestered C stored into the soil. The low amount of C sequestered in the soil following the addition of SOMW was attributed to its richness of moisture and easily degradable compounds that triggered the mineralization processes controlled by the soil microbial community. Although the 8 years of amendment produced a higher fruit yields than the control, no difference occurred between the characteristics and the oil content of the olive fruits. Only the total phenol content for the oil obtained from the SOMW-treated plots was significantly higher. The other considered fruit characteristics did not show significant differences.

Biochemical activity and chemical-structural properties of soil organic matter after 17 years of amendments with olive-mill pomace co-compost

This study evaluates soil fertility, biochemical activity and the soil's ability to stabilize organic matter after application of composted olive-mill pomace. This organic amendment was applied in two different olive groves in southern Spain having different soil typologies (carbonated and silicic). Olive grove soils after 17 years of organic management with application of olive-mill pomace co-compost were of higher quality than those with conventional management where no co-compost had been applied. The main chemical parameters studied (total organic carbon, total nitrogen, available phosphorus, exchangeable bases, cation exchange capacity, total extractable carbon (TEC), and humic-to-fulvic acids ratio), significantly increased in soils treated with the organic amendment. In particular, the more resistant pool of organic matter (TEC) enhanced by about six and eight fold in carbonated and silicic soils, respectively. Moreover, the amended silicic soils showed the most significant increases in enzyme activities linked to C and P cycles (β-glucosidase twenty-five fold higher and phosphatase seven fold higher). Organic management in both soils induced higher organic matter mineralization, as shown by the higher pyrrole/phenol index (increasing 40% and 150% in carbonated and silicic soils, respectively), and lower furfural/pyrrole index (decreasing 27% and 71% in carbonated and silicic soils, respectively). As a result of mineralization, organic matter incorporated was also more stable as suggested by the trend of the aliphatic/aromatic index (decreasing 36% and 30% in carbonated and silicic soils, respectively). Therefore, management system and soil type are key factors in increasing long-term C stability or sequestration in soils. Thus application of olive-oil extraction by-products to soils could lead to important mid-to -long-term agro-environmental benefits, and be a valuable alternative use for one of the most widespread polluting wastes in the Mediterranean region.

English

Experiments were carried out under field conditions to evaluate the effects of composted tannery sludge (CTS) on soil pH, electric conductivity (EC) and soil organic matter (SOM) content after three years of amendment. The CTS was applied at 0, 2.5, 5.0, 10.0 and 20.0 ton ha-1. In each year, soil samples were collected 60 day after CTS amendment. After three years, the CTS increased about 5, 46 and 69% of the soil pH, EC and SOM content as compared with the control. Consecutive amendment of crescent rates of CTS promotes linear increases in soil pH, electric conductivity and organic matter content.   Key words: Composting, industrial wastes, salinity soil.

Effects of long-term soil amendment with sewage sludges on soil humic acid thermal and molecular properties

Sewage sludges are frequently used as soil amendments due to their high contents of organic matter and nutrients, particularly N and P. However, their effects upon the chemistry of soil humic acids, one of the main components of the soil organic matter, need to be more deeply studied in order to understand the relation between organic matter structure and beneficial soil properties. Two sewage sludges subjected to different types of pre-treatment (composted and thermally dried) with very different chemical compositions were applied for three consecutive years to an agricultural soil under long-term field study. Thermal analysis (TG–DTG–DTA) and solid-state 13C NMR spectroscopy were used to compare molecular and structural properties of humic acids isolated from sewage sludges, and to determine changes in amended soils. Thermally dried sewage sludge humic acids showed an important presence of alkyl and O/N-alkyl compounds (70%) while composted sludge humic acids comprised 50% aromatic and carbonyl carbon. In spite of important differences in the initial chemical and thermal properties of the two types of sewage sludges, the chemical and thermal properties of the soil humic acids were quite similar to one another after 3 years of amendment. Long-term application of both sewage sludges resulted in 80–90% enrichment in alkyl carbon and organic nitrogen contents of the soil humic acid fraction.