Fertility Response of Potato to Municipal Wastewater and Inorganic Fertilizers

This study evaluated fertilizer contribution of municipal wastewater on potato (Solanum tuberosum L.) cultivation in a split-plot experiment having two factors: water quality with 5 levels and fertilizer with 2 levels. Irrigation by raw wastewater supplied 16, 13, 13, 23, 1.7, and 83% of nitrogen (N), phosphorus (P), potassium (K), sulfur (S), zinc (Zn), and boron (B) requirement of potato, respectively. Wastewater compared to freshwater, improved plant height, vigority, area coverage, leaf area index (LAI), stem per plant, number and weight of tuber per plant, above-ground dry matter (ADM), and tuber yield of potato. Averaged over 3 years, irrigation by 75 and 100% (raw) wastewater with recommended standard fertilizers produced the maximum, but identical, tuber yield. Wastewater raised N, P, and K contents in potato plants and tubers. Irrigation by wastewater could reduce the fertilizer requirement of potato by 10–15%. However, it caused high accumulation of total coliform (TC) and faecal coliform (FC) on potato skin, restricting the use of the produce.     

Physicochemical Properties of Soil under Wheat Cultivation by Irrigation with Municipal Wastewater in Bangladesh

Irrigation with wastewater provides the opportunity to solve the problems of its disposal, reuse and water conservation. Freshwater, differentially diluted wastewater and undiluted wastewater (hereafter called wastewater) were used to grow wheat in sandy loam soil under fertilized and unfertilized conditions at the experimental farm of Bangladesh Agricultural University, Bangladesh. Fresh groundwater and wastewater of Mymensingh municipality were used to irrigate a wheat field for three consecutive years to examine the effects of wastewater application on soil properties. In this study, the properties of wastewater-irrigated soil were compared with freshwater-irrigated soil. The application of wastewater reduced the bulk density of the surface soil by 1.92% and augmented the porosity by 5.89%. The unsaturated hydraulic conductivity and water retention capacity of the soil were improved under wastewater irrigation. Soil pH increased due to wastewater application but decreased, to a smaller extent, due to fertilizer application. Soil electrical conductivity (EC) increased both with wastewater and with fertilizer application; both parameters changed significantly in the 0–20 cm soil layer. However, at the deeper layers, they were not affected by wastewater application. The organic carbon (C) and total nitrogen (N) level of the soils were higher under wastewater irrigation than under freshwater-irrigated soil. The organic C increased by 23.93% under wastewater irrigation in the top 20 cm soil layer. The N content of the soil showed similarities with the organic C contents. Available P and S concentrations were greater in the soil irrigated with wastewater compared with the soil irrigated with freshwater. The exchangeable cations – sodium (Na), potassium (K), calcium (Ca) and magnesium (Mg) – also increased significantly with wastewater application. Thus, farmers are advised for irrigation with municipal wastewater to ease pressure on freshwater and to improve soil fertility.     

Changes in Soil Properties in Response to Irrigation of Potato by Urban Wastewater

This study evaluated the physicochemical changes in the soil of potato field that was irrigated by fresh water, differentially diluted wastewater and undiluted wastewater (hereafter called wastewater). The potato crop was cultivated for consecutive three seasons under fertilized and unfertilized conditions. The wastewater contained higher concentrations of organic carbon (C), nitrogen (N), phosphorus (P), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), sulfur (S), zinc (Zn) and boron (B) and lower concentrations of heavy metals. In this study, properties of wastewater-irrigated soil were compared with fresh water-irrigated soil. The application of wastewater reduced the bulk density of the surface soil by 2.83% and augmented the porosity by 6.02%. The unsaturated hydraulic conductivity and water retention capacity of the soil were improved under wastewater irrigation. Soil pH increased due to wastewater application but decreased, to a smaller extent, due to fertilizer application. Soil EC increased both with wastewater and fertilizer application; both parameters changed significantly in the top 0–15 cm soil layer. But, at the deeper layers, they were not affected by wastewater application. The organic C, total N, available P and S of the soils increased significantly (p = 0.05) when potato field was irrigated with raw wastewater. The organic C increased by 23.80% under wastewater irrigation in the top soil layer. The N content of the soil showed similarities with the organic C contents. Exchangeable Na, K, Ca, Mg; Zn and B of the soil also increased significantly with wastewater application. So, irrigation with urban wastewater is suggested to improve soil fertility as well as to ease pressure on the fresh water in the area of water scarcity.     

Wastewater Re-Use for Croton in Substrates Amended with Zeolitic Tuff

ABSTRACT

Treated wastewater was compared with tap water for irrigation of croton (Codiaeum variegatum Blume cv. ‘Petra’) in substrates consisting of 1 peat moss: 1 perlite (PP) or 1 soil: 1 sand (SS), alone or supplemented with zeolitic tuff at a ratio of 3:1 (PPZ and SSZ). Substrates were allowed to reach 80% of available water before the plants were irrigated with wastewater or tap water. Results indicated that neither water quality nor substrate affected plant width, leaf area, shoot fresh weight, or root length or weight. Wastewater increased stem diameter; node and leaf number; tissue nitrogen (N); sodium (Na); and chloride (Cl); substrate electrical conductivity (EC); phosphorus (P); Na, Cl, and leachate EC; and concentrations of Na, Cl, NO₃ ^?, and NH₄ ⁺. Root count, tissue Na, substrate potassium (K) and Na, and leachate pH were higher for zeolite-containing substrates. Shoot dry weight and tissue contents of N and P were the highest for wastewater-irrigated PP and PPZ. Wastewater-irrigated plants in PP and tap water-irrigated plants in PPZ exhibited the highest K content. The highest level of tissue Cl was recorded for SS. Tap water-irrigated PPZ had the highest pH and K concentration. Wastewater-irrigated PP, PPZ, and SS exhibited the highest contents of N, Na, and Cl, respectively. Based on the results, amendment of the substrate with zeolitic tuff is recommended to offset the adverse effect of salinity associated with wastewater.     

Effects of tanneries wastewater on chemical and biological soil characteristics

Effluents from leather processing, a major industry that produces up to 64320 t wastewater year⁻¹ in the town of León (Guanajuato, Mexico), are normally discharged to the river Turbio without treatment. This water is downstream used to irrigate agricultural land. Tannery wastewater contains valuable nutrients, but also contaminants, such as salts and chromium (Cr), that might affect soil processes and crop production. We investigated how almost 25 years of irrigation of agricultural land with water from the river Turbio affected soil characteristics, dynamics of carbon (C) and nitrogen (N), and microbial biomass C. Soil sampled from three adjacent fields irrigated with tannery effluent (soil A), in the vicinity irrigated with well water (soil B), and at a distance of 10 km from the irrigation canals (soil C), was characterized while dynamics of C and N were measured in an aerobic incubation experiment. Irrigation with water from the river Turbio for over 25 years had significantly increased the electrolytic conductivity from 0.64 to 2.29 dS m⁻¹, organic C and total N content two-times, total concentration of Cr four-times, copper (Cu) two-times and sodium (Na) six-times in the clayey soils (P < 0.05). Microbial biomass was two-times larger in soil A than in soil C, while the activity of proteases and hydrolases releasing ninhydrin positive compounds and organic C appeared not to be affected. The concentrations of ammonium (NH₄⁺) and nitrate (NO₃⁻) were not significantly different between the soils. The concentration of nitrite (NO₂⁻) was approximately twice larger in soil A than in soil C (P < 0.05). Although there appeared to be no adverse impact on soil characteristics and microbial biomass, oxidation of NO₂⁻ was inhibited indicating that the biological functioning of the soil might be affected. The increase in heavy metals in soil was limited, but continued irrigation with water from the river Turbio might increase sodicity and salinity that could deteriorate soil and pose a threat to future crop production.     

Comparative effect of human urine and ammonium nitrate application on maize (Zea mays L.) grown under various salt (NaCl) concentrations

The present study investigates the effect of urine and ammonium nitrate on maize (Zea mays L.) vegetative growth, leaf nutrient concentration, soil electrical conductivity, and exchangeable‐cations contents under various concentrations of NaCl in a soil substrate. The experiment was arranged in a completely randomized block design with eight replications under greenhouse conditions. The experimental soil substrate was made from a 1 : 1 : 1 volume‐ratio mixture of compost, quartz sand, and silty‐loam soil. Salinity was induced by adding 0, 15, and 30 mL of 1 M NaCl solution per kg of substrate to achieve an electrical conductivity (EC) of 1.3 (S0), 4.6 (S1), and 7.6 (S2) dS m^–1. Nitrogen sources were urine and ammonium nitrate applied at 180 and 360 mg N (kg soil substrate)^–1. Basal P and K were added as mono potassium phosphate in amounts equivalent to 39 mg P and 47 mg K (kg substrate)^–1, respectively. In the S0 treatment, a 3‐fold increase in EC was measured after urine application compared to an insignificant change in ammonium nitrate–fertilized substrates 62 d after sowing. Under saline conditions, application of 360 mg N (kg soil)^–1 as urine significantly decreased soil pH and maize shoot dry weight. At the highest salt and N dose (S2, N360) 50% of urine‐fertilized plants died. Regardless of salinity there was no significant difference between the two fertilizers for investigated growth factors when N was supplied at 180 mg (kg soil)^–1. Leaf N and Ca contents were higher after urine application than in ammonium nitrate–fertilized plants. At an application rate of 180 mg N (kg soil)^–1, urine was a suitable fertilizer for maize under saline conditions. Higher urine‐N dosages and/or soil salinity exceeding 7.6 dS m^–1 may have a deleterious effect on maize growth.     

Treated municipal wastewater for citrus irrigation 1

Treated, reclaimed municipal wastewater was evaluated on citrus trees in central Florida for over six years. The effects of irrigation with reclaimed wastewater on soil water content, soil chemical analysis, leaf mineral status, and fruit quality were compared with those of irrigation with well water. Irrigation with reclaimed water increased mineral residues in the soil profile, altered leaf mineral concentration and fruit quality, and promoted better tree performance and more weed growth relative to irrigation with well water. Higher accumulation of nitrogen (N), potassium (K), calcium (Ca), and magnesium (Mg) in soils irrigated with reclaimed water were not significantly reflected in leaf mineral status. Although leaf sodium (Na), chloride (Cl), and boron (B) concentrations were noticeably higher in reclaimed water treatments than in those of well water, they are still far below the toxicity levels. This highly treated wastewater in central Florida has been found to be a very safe and good option for increasing water supplies, but not a significant source of plant nutrients to citrus trees.     

Soil properties and N application effects on microbial activities in two winter wheat cropping systems

The application of mineral N fertilizers may influence biologically mediated processes that are important in nutrient transformations and availability. This study was conducted to assess the effect of N application on microbial activities in irrigated and non-irrigated winter wheat systems. Carbon decomposition and microbial biomass C in soils with three N application rates (0, 150, and 300 kg N ha^–1 as urea) were measured over 40 days in a laboratory incubation experiment. Carbon, N, and P contents in the soil under the irrigated wheat were higher than those in the soil under the non-irrigated wheat. The reverse trend was observed for soil pH and Ca and Mg contents. However, soils from the two systems had similar C/N ratios. Carbon decomposition and microbial biomass C in the soil under the irrigated wheat increased significantly (p <0.05). Increasing rates of N fertilizer resulted in higher C decomposition and microbial biomass C levels in both soil systems. Results indicate that different wheat cropping systems affect soil properties that will then have an impact on C turnover in the soil. Moreover, the irrigated wheat system favors soil conditions required for a faster C turnover. In conclusion, it is likely that due to positive effects on microbial activity, N fertilization will increase nutrient cycling and, subsequently, crop productivity will improve in N-poor soils.     

Effects of municipal solid waste compost,farmyard manure and chemical fertilizers on wheat growth,soil composition and soil bacterial characteristics under Tunisian arid climate

The use of municipal solid waste compost (MSWC) as soil organic amendment is of an economic and environmental interest. However, little is known about the effectiveness of MSWC application on agricultural soil in northern Africa arid climate. We assessed the impact of five years' applications of different organic and mineral fertilizers on wheat grain yields and soil chemical and microbial characteristics. Soils were treated with MSWC at rates of 40 (C1) and 80 (C2) Mg ha^?1, farmyard manure at a rate of 40 Mg ha^?1 (M), chemical fertilizers (Cf) and the combinations (C1Cf, C2Cf, MCf). Wheat grain yield was enhanced with all amendments. Parallel increases of heavy metal levels and faecal coliform were also recorded except for Cf treatments. Based on wheat grain yield, heavy metal and faecal coliform data, we determined the treatment effectiveness index (E_xx), calculated by dividing the pollutant increase ratio by the grain yield increase ratio. The treatment effectiveness index E_C1 indicated lower faecal and heavy metal pollution with positive gains in wheat yields. Despite polluting effects on soil determined by the different treatments, no significant differences between treatments were observed in total bacterial count and soil bacterial community structure, as shown by 16S rRNA gene PCR-denaturing gradient gel electrophoresis banding patterns and 16S rRNA gene Length Heterogeneity-PCR analysis. According to the collected data, the use of MSWC at a rate of 40 Mg ha^?1 might be recommended.     

Soil aggregation and distribution of carbon and nitrogen in different fractions under long-term application of compost in rice–wheat system

Soil organic matter improves the physical, chemical and biological properties of soil, and crop residue recycling is an important factor influencing soil organic matter levels. We studied the impact of continuous application of rice straw compost either alone or in conjunction with inorganic fertilizers on aggregate stability and distribution of carbon (C) and nitrogen (N) in different aggregate fractions after 10 cycles of rice–wheat cropping on a sandy loam soil at Punjab Agricultural University research farm, Ludhiana, India. Changes in water stable aggregates (WSA), mean weight diameter (MWD), aggregate-associated C and N, total soil C and N, relative to control and inorganically fertilized soil were measured. Total WSA were significantly (p = 0.05) higher for soils when rice straw compost either alone or in combination with inorganic fertilizers was applied as compared to control. The application of rice straw compost either alone or in combination with inorganic fertilizers increased the macroaggregate size fractions except for 0.25–0.50 mm fraction. The MWD was significantly (p = 0.05) higher in plots receiving rice straw compost either alone at 8 tonnes ha⁻¹ (0.51 mm at wheat harvest and 0.41 mm at rice harvest) or at 2 tonnes ha⁻¹ in combination with inorganic fertilizers (0.43 and 0.38 mm) as compared to control (0.34 and 0.33 mm) or inorganically fertilized plots (0.33 and 0.31 mm). The macroaggregates had higher C and N density compared to microaggregates. Application of rice straw compost at 2 tonnes ha⁻¹ along with inorganic fertilizers (IN + 2RSC) increased C and N concentration significantly over control. The C and N concentration increased further when rice straw compost at 8 tonnes ha⁻¹ (8RSC) was added. It is concluded that soils can be rehabilitated and can sustain the soil C and N levels with the continuous application of rice straw compost either alone or in combination with inorganic fertilizers. This will also help in controlling the rising levels of atmospheric carbon dioxide.     

Sustainability of organic fertilization of macadamia with macadamia husk‐manure compost

Abstract

Macadamia husk‐manure compost was evaluated as an organic fertilizer for the production of macadamia in an experiment over four years at irrigated and unirrigated sites on the MacFarms of Hawaii orchard. The treatments were (1) Fertilizer, a combination of solid and liquid chemical fertilizers applied based on leaf and soil analysis, (2) Compost, 10,000 kg ha^‐1 of a macadamia husk‐cattle manure compost alone applied annually between July and October, and (3) Compost+, compost plus mineral fertilizers applied based on leaf and soil analysis. In‐shell nut and kernel yield and quality were higher at irrigated than unirrigated sites, but were not significantly affected by the treatments. Change in leaf nutrient composition appears minimum except for slightly lower nitrogen (N) and boron (B) at two orchard sites for the compost treatment. Compost increased soil pH, total ion exchange capacity, soil organic matter, potassium (K), calcium (Ca), magnesium (Mg) at all sites, and sodium (Na) at irrigated sites. Soil nitrate (NO)‐N was lower in the compost treatment. Fertilization with compost was not profitable because the cost of compost application exceeded conventional fertilization cost tenfold for MacFarms, the largest macadamia farm in the United States.     

Effect of organic and mineral fertilizers on soil respiration and enzyme activities of two Mediterranean horticultural soils

The effects of municipal food waste compost addition and mineral fertilization on selected soil microbiological activities were investigated during 3 years of reiterated treatments on two Mediterranean agricultural soils with different organic carbon content. Compost at 15, 30 and 45 t ha⁻¹ (dry matter), mineral (NPK) fertilizers and combined fertilizers with 15 t ha⁻¹ of compost plus two reduced doses of mineral N were applied to both soils. At both sites, organic amendment increased soil respiration, fluorescein diacetate hydrolysis, phosphatase and arylsulphatase activities. The differences in soil microbial activities among treatments, found after 3 years of repeated treatments, were attributable to the variations of soil organic C content and to the impact of soil tillage. Our results show that, in Mediterranean intensively cultivated agroecosystems, annual organic amendments improve the microbial activity of soil and produce cumulative effects, suggesting the usefulness of repeated high-rate compost applications.     

Physico-chemical indicators and microarthropod communities as influenced by no-till, conventional tillage and nitrogen fertilisation after four years of continuous maize

A multidisciplinary study was carried out over four years in Northern Italy on a silt loam under continuous maize. The experimental design was a split-plot with four replicates; the main factor was the soil management system, conventional tillage (CT) or no-tillage (NT), while the secondary factor was N fertilisation. At the end of the trial, soil samples were taken from all plots at four depths (from 0 to 20 cm). In these samples the following were determined: pH, soil organic carbon (SOC), total N, available P, exchangeable K, cation exchange capacity (CEC), electrical conductivity (EC) and water aggregate stability (WAS). Soil compaction was measured during the last three years, after maize harvesting. To study the microarthropod community, soil samples (0–10 cm depth) were taken six times over the four years. Our results show that NT significantly increased SOC (+15.8%), total N (+9.6%), C/N (+5.3%), exchangeable K (+37.1%) and WAS (+64.8%). The stratification ratio for exchangeable K reached 2.15 for NT plots. N fertilisation, on the other hand, had no significant effect on most of the physico-chemical indicators, except for pH, CEC and EC. Soil compaction was significantly higher for NT compared with CT up to a depth of 25–30 cm. During the last year, interesting reductions in soil penetration resistance for NT were measured, up to 300–430 kPa in the 2.5–12.5 cm layer. As for the microarthropods, Acari were more sensitive to tillage compared with Collembola, and the Wardle V index proved to be a good indicator of the response to tillage. N fertilisation with 300 kg N ha⁻¹ had a negative effect on the total microarthropod abundance. The Shannon diversity index gave fluctuating and significantly different results: over the years results were split alternately between the two tillage systems. The QBS-ar index, calculated for all the four years of the study, ranged between 48 and 72, values typical of intensively cultivated soils. The results obtained suggested that it was not influenced by the tillage system. Therefore, this index seems to be unsuitable for detecting the influence of tillage management and N fertilisation on the microarthropod community.     

Variation of enzyme activities, CO2 evolution and redox potential in an Eutric Histosol irrigated with wastewater and tap water

An Eutric Histosol soil was irrigated for 4 years with municipal wastewater to compare its characteristics with a soil under natural rainfall that had never received wastewater and a soil that was irrigated with normal tap water. Four years irrigation of the soil with wastewater caused significant (P<0.001) increase in dehydrogenase, urease, acid and alkaline phosphate activities and CO₂ evolution, and reduced the redox potential (P<0.05). The influence of treatments and plant cover on soil properties were significant (P<0.05) under both salix and grasses, except for few properties (redox potential and urease and alkaline phosphatase activities). It is suggested that, although different toxicants, e.g. heavy metals, may accumulate in wastewater-treated soils, enrichment of soil with organic substances and nutrients stimulated CO₂ evolution and enzyme activities in the irrigated soil.     

Relationships between electrical conductivity and fertilizer levels in an azalea Liner growing medium

Abstract

Regression analyses were used to survey the effects of extractable NO₃‐N, P, K, Ca, Mg, and soil pH on electrical conductivity (EC) in a 1: 1: 1 (v/v/v) peat‐sand‐perlite azalea (Rhododendron sp.) growing medium amended with soluble 21–3–6 (N‐P‐K) or slow‐release 18–3–6 fertilizer sources. Simple linear correlations indicated a high degree of relationship between NO₃‐N, P, and K versus EC (r=0.95**, 0.79**, and 0.79**, respectively). Partial regression coefficients suggested that NO.‐N was the primary ionic species affecting EC. The correlations between EC versus P and K were apparently related to their intercorrelation with NO₃ ‐N, associated with the use of N‐P‐K fertilizers. These relationships were constant across fertilizer sources. The results demonstrate a potential for the use of soil EC in the estimation of NO₃‐N in soilless rooting media.     

Soil carbon and nutrient pools, microbial properties and gross nitrogen transformations in adjacent natural forest and hoop pine plantations of subtropical Australia

Background, Aims, and Scope  An improved understanding of important soil carbon (C) and nutrient pools as well as microbial activities in forest ecosystems is required for developing effective forest management regimes underpinning forest productivity and sustainability. Forest types and management practices can have significant impacts on soil C and nutrient pools as well as biological properties in forest ecosystems. Soil C and nutrient pools were assessed for adjacent natural forest (NF), first rotation (1R) (50-year-old), and second rotation (2R) (1-year-old) hoop pine (Araucaria cunninghamii Ait. ex D. Don) plantations in southeast Queensland of subtropical Australia. Materials and Methods  Five transects spaced 3 m apart with 9 sampling points along each transect were selected (9.6 m × 12.0 m each site), with 45 soil cores (7.5 cm in diameter) collected and separated into 0–10 and 10–20 cm depths. These soils were analysed for total C, total nitrogen (N), C (δ¹³C) and N (δ¹⁵N) isotope composition. The 0–10 cm soils were analysed for pH, CEC, exchangeable cations, total P and total K, and assayed for microbial biomass C and N, respiration, metabolic quotient, potential mineralizable N (PMN), gross N mineralization (M) and immobilization (I). Results  Total C and N in 0–10 cm soils were higher under NF and 1R plantation than under 2R plantation, while they were highest in 10–20 cm soils under NF, followed by the 1R and then 2R plantation. δ¹³C was lower under NF than under the plantations, while δ¹⁵N was higher under NF than under the plantations. Total P was the highest under NF, followed by the 1R and then 2R plantation, while total K was higher under the 2R plantation. No significant differences were detected for pH, CEC, exchangeable cations, microbial C and N, respiration and metabolic quotient among the 3 sites. PMN and M were higher under NF, while I was the highest under the 2R plantation, followed by the NF and then 1R plantation. Discussion  Soil total C and N in 0–10 cm depth were significantly lower under 2R hoop pine plantation than those under NF and 1R hoop pine plantation. There were significant reductions in soil total C and N from NF to 1R and from 1R to 2R hoop pine plantations in 10–20 cm depth. This highlights potential N deficiency in the 2R hoop pine plantations, and application of N fertilizers may be required to improve the productivity of 2R hoop pine plantations. There were no significant differences in other soil chemical and physical properties in 0–10 cm depth among the 3 sites under NF, 1R and 2R hoop pine plantations, except for soil total P and K. Soil microbial biomass C, CO₂ respiration and metabolic quotient did not differ among the 3 sites assessed, perhaps mainly due to these biological variables being too sensitive to variations in soil chemical and physical properties and thereby being associated with a larger variability in the soil biological properties. However, soil potential mineralizable N, gross N mineralization and immobilization were rather sensitive to the conversion of NF to hoop pine plantation and forest management practices. Conclusions  Total C and N in the top 20 cm soil were highest under NF, followed by 1R and then 2R hoop pine plantations, indicating that N deficiency may become a growth-limiting factor in the 2R hoop pine plantations and subsequent rotations of hoop pine plantation. The sample size for soil δ¹³C seems to be much smaller than those for soil total C and N as well as δ¹⁵N. The significant reductions in soil total P from NF to 1R and then from 1R to 2R hoop pine plantations highlight that P deficiency might become another growth-limiting factor in the second and subsequent rotations of hoop pine plantations. Soil microbial properties may be associated with large spatial variations due to these biological properties being too sensitive to the variations in soil chemical and physical properties in these forest ecosystems. Recommendations and Perspectives  Soil potential mineralizable N, gross N mineralization and immobilization were useful indices of soil N availability in response to forest types and management practices. The sampling size for soil δ¹³C was much smaller than the other soil chemical and biological properties due to the different patterns of spatial variation in these soil properties.     

Treated Industrial Wastewater Effects on Chemical Constitution Maize Biomass,Physicochemical Soil Properties,and Economic Balance

Irrigation with treated wastewaters can improve nutrient levels and yield of crops planted on degraded soils. This study evaluated how irrigation with treated industrial wastewater affected biomass production and nutrition of maize plants and physio-chemical properties of a degraded soil. The experiment was conducted in a greenhouse using PVC columns. Treatments consisted of 8 treatments irrigated with clean water and increasing doses of N and P, and 8 treatments with 4 proportions of wastewater irrigation (25%, 50%, 75% and 100% v/v). In general, maize biomass did not differ between irrigation water sources. Differences were largely associated with N nutrition. We observed increases in concentrations of N, P, K, S, Mn, Na, Cu, and Zn in tissue of maize under irrigation with wastewater. The addition of treated wastewater increased the P and Na concentrations, and EC values in the soil without affecting clay dispersion in water. An associated economic analysis indicated that wastewater irrigation would not be economically feasible without including environmental benefits. In southern Brazil, the proportion of irrigation water that is wastewater should not exceed 50%.     

Effect of conjoint use of bio-organics and chemical fertilizers on yield,soil properties under French bean–cauliflower-based cropping system

This study investigates the effect of conjoint use of bio-organics (biofertilizers + crop residues + FYM) and chemical fertilizers on yield, physical–chemical and microbial properties of soil in a ‘French bean–cauliflower’-based cropping system of mid hills of the north-western Himalayan Region (NWHR) of India. Conjoint bio-organics at varied levels of NPK chemical fertilizers increased yield of ‘cauliflower’ over corresponding single application. Incorporation of crop residues with 75% of the recommended NPK application resulted in the highest yield (19 t ha^?1). Conjoint use of bio-organics produced a yield (15.65 t ha^?1), which was statistically on a par with 75% of the recommended NPK application alone. This indicated a saving of 75% NPK chemical fertilizers. In the case of ‘French bean’, the effect was non-significant. The results also showed significant higher soil available N (351.3 kg ha^?1) under 75% NPK + biofertilizers, whereas the highest soil available K (268.3 kg ha^?1) was recorded under 75% NPK + crop residues. Lowest bulk density (1.03 Mg m^?3), highest water holding capacity (36.5%), soil organic matter (10.6 g kg^?1), bacterial (4.13 × 10⁷ cfu g^?1) and fungal (6.3 × 10⁷ cfu g^?1) counts were recorded under sole application of bio-organics. According to our study, we concluded that the combination of NPK fertilizers and bio-organics increased yield except French bean, soil available N, K and saved chemical fertilizers under ‘French bean–cauliflower’-based cropping system.     

A preliminary watershed scale soil quality assessment in north central Iowa, USA

Soil quality assessment has been recognized as an important step toward understanding the long-term effects of conservation practices within agricultural watersheds. Our objective was to assess soil quality within the South Fork watershed of the Iowa River using various indicators and assessment approaches. Soil samples were collected during 2003 and 2004 from 29 areas of 32 ha (80 acres) each along two transects traversing the watershed. Soil pH, Mehlich III extractable P, K, Ca and Mg, electrical conductivity (EC), total organic carbon (TOC), and total N (TN) were measured. The Soil Management Assessment Framework (SMAF) was used to compute a soil quality index (SQI), while soil loss, the soil tillage intensity rating (STIR), N-leaching potential, and soil conditioning index (SCI) were determined for each sampling area using the 2003 version of the Revised Soil Loss Equation (RUSLE2). Overall, there were no soil fertility limitations within the watershed based on an average pH of 6.96 and extractable P and K levels of 36 and 162 mg kg⁻¹, respectively. Soil loss, STIR, N-leaching, and SCI averaged 1.13 Mg ha⁻¹, 68, 3, and 0.4, respectively. The SMAF analysis indicated soils within the watershed were functioning at 87% of their full potential. The lowest indicator score was associated with TOC (0.60) because the average value was only 28.4 g kg⁻¹. The SCI and SQI indices were positively correlated although since it used measured data, the SMAF appears to provide more information about the effects of management practices within the watershed. Soils in upper landscape positions had lower TOC and C:N ratios indicating an increased risks for both erosion and for nitrate leaching. Management of soils on hilltops may be the most effective way to minimize N and P losses within the watershed.     

Nitrous oxide emission,global warming potential,and denitrifier abundances as affected by long-term fertilization on Mollisols of Northeastern China

ABSTRACT

A long-term field experiment was performed to assess the effects of fertilization regimes on greenhouse gas emissions, soil properties, soil denitrifies, and maize (Zea mays) grain yield on Mollisols of Northeastern China. Chemical nitrogen (N), phosphorus (P), and potassium (K) fertilizers plus pig manure (MNPK) treatment significantly increased soil N₂O emissions by 29.9–226.4% and global warming potential (GWP) by 29.8–230.7% compared to unfertilized control (CK), chemical N fertilizer only (N), chemical N, P, and K fertilizers (NPK) and chemical N, P, and K fertilizers plus corn straw (SNPK) treatments. However, the MNPK treatment yielded similar greenhouse gas intensity (GHGI) as compared with other treatments, mainly due to higher maize grain yield. There were also higher gene copy numbers of nirK, nirS, and nosZ in topsoil (0–20 cm depth) under MNPK treatment. Automatic linear modeling analysis indicated that main factors influencing soil N₂O emissions were soil organic carbon (SOC), NO₃^? content, and nirK gene abundance. Although the application of chemical fertilizers plus organic manure increases N₂O emissions due to higher N and C availability and nirK gene activity in the soil, this is still a promising fertilizer management due to its notable enhancement of maize grain yield and SOC content.