Changes in Physicochemical Properties and Enzyme Activities of Four Soils Following the Application of Alkaline Winery Wastewater over Three Simulated Irrigation Seasons

Changes of soil physico-chemical properties and enzyme activities in relation to grassland salinization

Aplicações sucessivas de lodo de esgoto em solos agrícolas podem promover alterações significativas em alguns atributos químicos dos solos. Tendo em vista essa possibilidade, o presente trabalho objetivou avaliar os efeitos de duas aplicações sucessivas de doses crescentes de lodo de esgoto sobre os teores de carbono orgânico, condutividade elétrica, pH e CTC ao pH atual de um Latossolo Amarelo distrófico cultivado com cana-de-açúcar. O experimento foi realizado nos anos agrícolas 1996/97 e 1997/98: no primeiro ano, além dos tratamentos calagem + adubação mineral e testemunha, foram aplicadas em área total doses equivalentes a 33, 66 e 99 Mg ha-1 (base seca) de lodo de esgoto. Em 1997/98, o lodo foi reaplicado em doses equivalentes a 37, 74 e 110 Mg ha-1 (base seca). As aplicações de lodo de esgoto promoveram, em ambos os anos agrícolas, aumentos imediatos nos teores de C-orgânico, condutividade elétrica e pH do solo. A partir deste ponto, foram observados decréscimos de C-orgânico no decorrer dos dois anos agrícolas, cujos dados ajustaram-se a um modelo de cinética de primeira ordem. A redução na taxa de decréscimo, por ocasião da segunda aplicação do lodo de esgoto, evidenciou o acúmulo relativo de C-orgânico no solo, decorrente das aplicações sucessivas do resíduo. Não houve indícios de efeitos cumulativos sobre a condutividade elétrica em decorrência da segunda aplicação de lodo, o que evidencia estreita relação, em função do tempo, entre o comportamento dessa variável na camada de incorporação do lodo, a ocorrência de chuvas e a lixiviação de sais, demonstrada pelos aumentos na CE nas camadas subsuperficiais do solo. Para o pH, por ocasião da segunda aplicação do lodo, os incrementos foram menores do que os observados em 1996/97, evidenciando o poder de tamponamento do solo. O lodo de esgoto aumentou a capacidade de troca de cátions do solo, porém esse aumento não foi proporcional à dose aplicada, tampouco devido à segunda aplicação. As alterações na CTC foram mais bem explicadas pelas variações no pH do que pelos acréscimos de C-orgânico.

The changes in the physicochemical properties of calcareous soils and the factors of arsenic (As) uptake by wheat were investigated after the cessation of effluent irrigation for nearly 20 years

Heavy metals are potentially toxic to soil microorganims and are suggested to decrease soil enzymatic activities. Changes in activity of acid phosphatase in root-zones of some tropical plants treated with a lead-containing industrial waste were studied in a glasshouse experiment. Tropical soil sample (from Gedongmeneng and Banjaragung, Lampung) thoroughly treated with an electronics industrial waste at 0 to 40 ton ha·1 and lime at 0 or 5 ton CaC03 ha·1 were cultured with corn (Zea mays L.), amaranth (Amaranthus tricolor L), and green kyllinga (Cyperus kyllinga). Changes in acid phosphatase activity, soil Pb concentration, and soil pH were measured after a 4-week growing period. Soil analysis showed that the activity of acid phosphatase was higher in Banjaragung soil than that in Gedongmeneng soil except in those cultured with green kyllinga. The activity of acid· phosphatase was in general higher in the root-zone of corn than those in the root-zone of amaranth and green kyllinga.The activity of acid phosphatase in both soils decreased with waste addition regardless of plant grown. This was in a good correlation with the increase in soil available Pb as waste was added. However, the decrease in the activity of acid phosphate as the soil pH increased by lime or waste addition suggested that the decrease in the phosphatase activity with waste addition was driven by the increase in soil pH rather than by the increase in the soil available Pb With waste 3dclitton.

Identification of cadmium phytoavailability in response to cadmium transformation and changes in soil pH and electrical conductivity

Peat moss is an organic substance corroded by sphagnum moss and has a pH of 3.0–4.0. Elemental sulfur is sulfated and oxidized by the action of bacteria to become sulfuric acid. These biological factors can alter the soil environment. Blueberries require soil with a pH of 4.5–5.2 and high organic matter content. In this experiment, we investigated whether different treatment rates of peat moss, elemental sulfur, and sulfur-oxidizing bacteria affect changes in soil pH, physicochemical properties, and electrical conductivity. We detected strong changes in soil pH as a reaction to the supply of peat moss, elemental sulfur, and sulfur-oxidizing bacteria. The pH of the soil when peat moss and elemental sulfur each were supplied was reduced. In addition, the pH decreased faster when elemental sulfur and sulfur-oxidizing bacteria were supplied together than elemental sulfur alone, satisfying an acidic soil environment suitable for blueberry cultivation. In this experiment, it is shown that peat moss, elemental sulfur, and sulfur-oxidizing bacteria are suitable for lowering soil pH. It was demonstrated that when elemental sulfur and sulfur-oxidizing bacteria were treated together, the pH decreased faster than when treated with peat moss. It could be economically beneficial to farmers to use elemental sulfur and sulfur-oxidizing bacteria, which are cheaper than peat moss, to reduce the pH of the soil.

To examine the effect of soil acidification on growth and nitrogen (N) uptake by maize in Ultisols. A clay Ultisol derived from Quaternary red earth and a sandy Ultisol derived from tertiary red sandstone were used in this study. A pot experiment was conducted with maize growing in the two Ultisols acidified to different pH values. Urea with 15N abundance of 10.11% was used to investigate the distribution of N fertilizer between soil and plant. Total N content and 15N abundance in plant and soil samples were determined by elemental analysis-isotope mass spectrometry. Critical soil pHs of 4.8 and 5.0 were observed for maize growing in the clay and sandy Ultisols, respectively. Below the critical soil pH, increasing soil pH significantly increased maize height and the yield of maize shoots and roots (both P < 0.05), but changes in soil pH showed no significant effect on maize growth above the critical soil pH in both Ultisols. Maize growing in the sandy Ultisol was more sensitive to changes in soil pH than in the clay Ultisol. Increase in the pH in both Ultisols also increased N accumulation in maize, the N derived from fertilizer in maize, physiological N use efficiency, and N use efficiency (NUE) by maize. Changes in soil pH had a greater effect on these parameters below the critical soil pH, compared to above. The change in soil pH had a greater effect on N accumulation in maize, the N derived from fertilizer in maize, and NUE in the sandy Ultisol than in the clay Ultisol. The NUE increased by 24.4% at pH 6.0, compared with pH 4.0 in the clay Ultisol, while the NUE at pH 5.0 was 4.8 times that at pH 4.0 in the sandy Ultisol. The increase in soil pH increased the ratio of N accumulation in maize/soil residue N and decreased the potential loss of fertilizer N from both Ultisols. Soil acidification inhibited maize growth, reduced N uptake by maize, and thus, decreased NUE. To maintain soil pH of acidic soils above the critical values for crops is of practical importance for sustainable food production in acidic soils.

In the production of the natural medicinal plant American ginseng, replantation typically fails due to continuous cropping obstacles. However, the cause is still not clear and needs more research. Soil samples were collected from (a) maize fields where American ginseng had never been planted, (b) fields where American ginseng had just been harvested, and (c) fields where maize had been planted for 2, 4 and 6 years respectively after American ginseng. We investigated the physicochemical properties, the enzymatic activities, and the soil microbial community structure and composition of the samples. We found that the content of soil salt, NH4+-N, and NO3−-N increased significantly in samples associated with the production of American ginseng, whereas the soil pH, carbon-to-nitrogen ratio, alkaline phosphatase, and cellulase activity all significantly decreased and gradually recovered to the pre-planting level. Moreover, the bacterial diversity decreased, while fungal diversity and richness increased; fungal richness continued to increase in farmlands replanted maize. The relative abundance of some microbial communities was changed significantly and was gradually restored with a longer time to replant maize. Pearson’s correlation analysis shown that significantly changed microbial communities were significantly associated with changes in soil pH, soil salt and nitrogen content, alkaline phosphatase, and cellulase activity. Changes in soil pH, soil salt and nitrogen content caused changes in microbial community structure and composition, as well as cellulase and alkaline phosphatase activity. These changes may cause the continuous cropping obstacles of American ginseng and may be improved by planting maize.

Urbanization has drastically changed soil properties, and an assessment of these changes is essential for soil management and soil health. The activities of urease, acid phosphatase, invertase and catalase, soil organic matter, pH, electrical conductivity (EC) and clay (&lt; 0.01 mm) content of urban soils under two land-uses in the central built-up area of the Shenzhen city were investigated, and multivariate analysis was used to study the relationship between soil enzymes and soil physical-chemical properties. The results showed that invertase activity in roadside soil was significantly higher than that in urban park soil, whereas catalase activity was significantly higher in urban park soil. Soil organic matter had significant positive correlation with activities of invertase, urease and acid phosphatase but not with catalase. Soil pH had a significant negative direct effect on urease and acid phosphatase activity, but the effect was counteracted by positive indirect effect of soil organic matter. Soil EC had a positive direct effect on activities of catalase and there was a significant correlation between soil EC and soil catalase activities. Soil organic matter, soil pH and EC were the major factors influencing activities of soil enzymes.

Global patterns of soil phosphatase responses to nitrogen and phosphorus fertilization

A field experiment was conducted in a sodic soil (Typic Halaquepts) of Kanpur, India, to explore possibilities of utilizing coal fly ash for the purpose of reclamation. Effectiveness of coal fly ash applied at the rate of 10 and 20 Mg ha‐1 on changes in physicochemical properties of soil and its ultimate effect on the yields of rice IR‐8 and wheat Sonalika grown in a sequence were evaluated. Changes in soil pH, electrical conductivity, Na saturation % of exchange complex, hydraulic conductivity, bulk density, stability index, and moisture retention characteristics were monitored after harvest of each crop. Results indicated that coal fly ash was effective for improving physicochemical properties of sodic soil, which in turn resulted in significant increase of yields for rice and wheat. Application of fly ash at the rate of 10 and 20 Mg ha‐1 improved paddy rice yields from 1.02 (control) to 2.85 and 3.38 Mg ha‐1 during 1979, and from 1.98 to 4.03 and 4.65 Mg ha‐1 during 1980, respectively. Similar...

Largely influenced by the passage of the Swamp Land Act of 1849, many wetlands have been lost in the coastal plain region of southeastern United States primarily as a result of drainage to convert land for agriculture. While further wetland conversion or loss is universally acknowledged, the process continues with little public recognition of the causes or consequences. This study examined changes in soil carbon, pH, and Mehlich extractable nutrients in soils following conversion of wetland to beef cattle pasture. To better understand the chemical response of soils during wetland conversion to beef cattle pasture, soil samples were collected from the converted beef cattle pastures and from the adjoining reference wetland. Soil samples were collected from eleven sites in the beef cattle pasture, and from four in the adjoining reference wetland. Data that were collected from the reference wetland sites were used as the reference/baseline data to detect potential changes in soil properties associated with the conversion of wetlands to beef cattle pastures from 1940 to 2002. Compared with the adjoining reference wetland, the beef cattle pasture soils in 2002, 62 years after being drained, exhibited: (1) a decrease in organic carbon, TOC (-172.3 g kg-1), nitrogen, TN (-10.1 g kg-1), water soluble phosphorus, WSP (-5.1mg kg-1), and potassium, K (-0.7 mg kg-1); (2) an increase in soil pH (+1.8 pH unit), calcium, Ca (+88.4 mg kg-1), magnesium, Mg (+7.5 mg kgc), manganese, Mn (+0.3 mg kg-1), and iron, Fe (+6.9 mg kg-1); and (3) no significant changes in sodium (Na), zinc (Zn), copper (Cu), and aluminum (Al). In 2002, the amount of TOC and the concentration of soil organic matter (OM) in pasture fields were significantly lower than the concentration in the reference wetland with average values of 7.8 ± 8 g kg-1 and 36 ± 26 g kg-1 and 180.1 ± 188 g kg-1 and 257 ± 168 g kg-1, respectively. It appeared that conversion of wetlands was proceeding toward a soil condition/composition like that of mineral soils. Overall, conversion of wetland had significant effects on soil carbon, pH, nitrogen, phosphorus, and extractable nutrients. Results of our study have shown a decrease in TOC, TN, WSP, and K and an increase in soil pH, Ca, Mg, Mn, and Fe. These results are important in establishing useful baseline information on soil properties in pasture and adjoining reference wetland prior to restoring and converting pasture back to its original wetland conditions as a major part of the restoration effort being underway.

The effect of soil pH on the exchangeability and solubility of soil cations (Ca, Mg, Na, K, and NH4‐N) and anions (NO3‐N, Cl, and P) was investigated for 80 soils, spanning a wide range in physical and chemical properties and taxonomic groups. This information is needed from environmental and agronomic standpoints to estimate the effect of changes in soil pH on leachability and plant availability of soil nutrients. Soils were incubated with varying amounts of acid (H2SO4) and base (CaCO3) for up to 30 days. Although acid and base amendments had no consistent effect on cation exchangeability (as determined by neutral NH4OAc), amounts of water‐soluble Ca, Mg, Na, K, NH4‐N, and P decreased, while NO3‐N and Cl increased with an increase in soil pH. The increase in cation solubility was attributed to an increase in the negative charge of the soil surface associated with the base addition. The change in surface electrostatic potential had the opposite effect on amounts of NO3‐N and Cl in solution, with increases in N mineralization with increasing soil pH also contributing to the greater amount of NO3‐N in solution. The decrease in P solubility was attributed to changes in the solubility of Fe‐, A1‐, and Ca‐P complexes. The logarithm of the amount of water‐soluble cation or anion was a linear function of soil pH. The slope of this relationship was closely related (R2 = = 0.90 ‐ 0.96) to clay content, initial soil pH, and size of the cation or anion pool maintaining solution concentration. Although the degree in soil pH buffering increased with length of incubation, no effect of time on the relationship between cation or anion solubility and pH was observed except for NO3‐N, due to N mineralization. A change in soil pH brought about by acid rain, fertilizer, and lime inputs, thus, affects cation and anion solubility. The impact of these changes on cation and anion leachability and plant availability may be assessed using the regression equations developed.

Soil enzyme activities in two forage systems following application of different rates of swine lagoon effluent or ammonium nitrate

During cultivation of legumes soil is acidified due to proton release from roots. As a consequence of proton release, plants accumulate organic anions which may, if returned and decomposed in the soil, neutralize the soil acids. Until now the detailed processes responsible for the change in soil pH after incorporation of plant material have not been completely understood. Using a pot experiment we studied the changes in acid and base in soil during growth of field beans (Vicia faba L. cv. Alfred) and after incorporation of the plant material into the soil. Soil pH was significantly decreased by field beans from 6.00 to 5.64 in a cultivation period of 45 days. Proton release amounted to 32.7 mmol H+ pot-1, which was approximately equivalent to the accumulated alkalinity in the plant shoots (34.4 mmol). Return of field bean shoots caused a significant soil pH increase from 5.64 to 6.29. Within 7 days more than 90% of the added alkalinity was released. After 307 days incubation, soil pH decreased to 5.86 due to nitrification. In a second experiment, maize leaves (Zea mays L.), containing various concentrations of nitrogen and at various alkalinities, were incorporated into the soil. Soil pH change was positively correlated to alkalinity and malate concentration and negatively correlated to total nitrogen and water-soluble organic nitrogen of incorporated leaves. It is concluded that the soil acidification caused by legume cultivation can be partly compensated for if crop residues are returned to the soil. Addition of plant material may initially cause an increase in soil pH due to decomposition of organic anions and organic nitrogen. Soil pH may decrease if nitrification is involved. The concentrations of nitrogen and alkalinity of added plant material are decisive factors controlling soil pH change after incorporation of plant material.