Xerollic Calciorthid Research Articles

Response of soil microbial activity and biodiversity in soils polluted with different concentrations of cypermethrin insecticide.

We performed a laboratory study into the effect of cypermethrin insecticide applied to different concentrations on biological properties in two soils [Typic Xerofluvent (soil A) and Xerollic Calciorthid (soil B)]. Two kg of each soil were polluted with cypermethrin at a rate of 60, 300, 600, and 1,200 g ha(-1) (C1, C2, C3, and C4 treatments). A nonpolluted soil was used as a control (C0 treatment). For all treatments and each experimental soil, soil dehydrogenase, urease, β-glucosidase, phosphatase, and arylsulphatase activities and soil microbial community were analysed by phospholipid fatty acids, which were measured at six incubation times (3, 7, 15, 30, 60, and 90 days). The behavior of the enzymatic activities and microbial population were dependent on the dose of insecticide applied to the soil. Compared with the C0 treatment, in soil A, the maximum inhibition of the enzymatic activities was at 15, 30, 45, and 90 days for the C1, C2, C3, and C4 treatments, respectively. However, in soil B, the maximum inhibition occurred at 7, 15, 30, and 45 days for the C1, C2, C3, and C4 treatments, respectively. These results suggest that the cypermethrin insecticide caused a negative effect on soil enzymatic activities and microbial diversity. This negative impact was greater when a greater dose of insecticide was used; this impact was also greater in soil with lower organic matter content. For both soils, and from these respective days onward, the enzymatic activities and microbial populations progressively increased by the end of the experimental period. This is possibly due to the fact that the insecticide or its breakdown products and killed microbial cells, subsequently killed by the insecticide, are being used as a source of energy or as a carbon source for the surviving microorganisms for cell proliferation.

Use of biostimulants on soil restoration: Effects on soil biochemical properties and microbial community

Four biostimulants (BS): WCDSs, wheat condensed distiller solubles; PA-HE, hydrolyzed poultry feathers; CGHE, carob germ enzymatic extract; and RB, rice bran extract were applied annually at 4.7 t organic matter (OM) ha −1 for a 3-year period to a Xerollic Calciorthid soil to evaluate their efficiency in soil restoration. Their effects on the plant cover, soil enzymatic activities and the structure of the soil microbial community by analysing phospholipid fatty acids (PLFAs) were determined. Application of BS that contain higher amounts of protein and higher percentage of peptides under 3 kDa had a greater effect on the soil biological properties, possibly due to the low molecular weight protein content can be easily assimilated by soil microorganisms. Following 3 years of successive soil amendment, the dehydrogenase activity was 4.6, 9.6, and 17.6% higher in PA-HE-amended soils than in the RB, CGHE and WCDS-amended soils, respectively. The urease activity was 5.3, 14.5, and 28.8% higher in PA-HE-amended soils than in the RB, CGHE and WCDS-amended soils, respectively. The phosphatase activity was 8, 15.3, and 20.2% higher in PA-HE-amended soils than in the RB, CGHE and WCDS-amended soils, respectively. The arylsulfatase activity was 16, 21.1, and 27.2% higher in PA-HE-amended soils than in the RB, CGHE and WCDS-amended soils, respectively. Total soil phospholipid fatty acid (PLFA) concentration was significantly ( p < 0.05) higher in BS-amended soil than control soil. Principal component analysis discriminated between the BS-amended soils, mainly based on content of lower molecular weight peptides. Thus, PA-HE and RB were grouped and differentiated from CGHE and WCDS, respectively. After 3 years of treatment, vegetal cover was 11.4, 17.7, 24.1, and 85.8% higher in PA-HE-amended soils than in the RB, CGHE, WCDS treatments and control soil. These results suggested that under semiarid climatic conditions the application of BS with higher amounts of protein (>50%) and a higher percentage of peptides under 0.3 kDa (>60%) notably increased the soil enzymatic activities, induced changes in microbial community because the protein with lower molecular weight can be more easily absorbed by soil microorganisms, and also favoured the establishment of vegetation, which will protect the soil against erosion and will contribute to its restoration.

Utilization of Vermicomposts in Soil Restoration: Effects on Soil Biological Properties

Increasingly, organic soil amendments are being examined for their potential use in soil restoration and for preventing soil erosion. Two vermicomposts, differing in their chemical nature (obtained from cow dung, CD, and green forage, GF), were applied annually for a period of 3 yr to a Xerollic Calciorthid soil located near Seville (Guadalquivir Valley, Andalusia, Spain) to evaluate the efficiency of these organic amendments in soil restoration. Their effects on the plant cover and biological properties (microbial biomass, soil respiration, and enzymatic activities such as dehydrogenase, urease, β‐glucosidase, phosphatase, and arylsulfatase) of the soil were determined. The organic wastes were applied at 3 and 6 Mg C ha−1, respectively. After 3 yr of successive soil amendment, the application of CD vermicompost to the soil had a greater effect on the soil biological properties than GF vermicompost. The final soil microbial biomass C, dehydrogenase, urease, β‐glucosidase, phosphatase, and arylsulfatase values were 28.3, 25.9, 12.6, 26, 12, and 14.2% higher in CD‐amended soils than in the GF‐amended soils. This may have been due to a greater labile fraction of organic matter in the CD than the GF vermicompost; however, the results obtained for the enzymatic activities stabilized in humic matrix mitigated that the highest values occurred in the soils amended with GF vermicompost with respect to those amended with CD vermicompost. This increased formation of enzymes immobilized in soils humic matrix may prolong any increase in soil enzymatic activities and plant cover produced by the amendment.

Effects of a vermicompost composted with beet vinasse on soil properties, soil losses and soil restoration

Abstract The use of organic rich wastes instead or as a complement of mineral fertilizers is considered a good environmental practice, provided that the organic wastes are not severely polluted (e.g. occurrence of heavy metals, organic pollutants and/or pathogens). However, the effect of a particular organic waste on soil properties, soil loss and soil restoration depends on its chemical composition. In particular, the application of fresh beet vinasse showed a detrimental impact on the soil's physical, chemical and biological properties, increasing soil loss and decreasing plant cover, probably because it contains high quantities of monovalent cations, such as Na+, which destabilize the soil structure. The main objective of this work was to study the effect of beet vinasse co-composted with a vermicompost (constituted by green forages) at rates of 5 and 10 t kg organic matter ha− 1, on physical (structural stability and bulk density), chemical (exchangeable sodium percentage) and biological (soil microbial biomass-C, soil respiration and soil enzymatic activities) properties of soils and, consequently, how its application may contribute to soil loss and soil restoration. The experiment was carried out for three years on a Xerollic Calciorthid located near Seville (Guadalquivir Valley, Andalusia, Spain). The co-composting of beet vinasse and green waste vermicompost had a positive effect on the soil's physical, chemical and biological properties, leading to a decrease in soil loss (31.2% compared with unamended soil) and an increase in plant cover (68.7% compared with unamended soil). These results suggest that the co-composting of beet vinasse with vermicomposts protects the soil and contributes to its restoration, thus representing a good strategy for recovering semiarid areas.

Tillage and cropping intensification effects on soil aggregation: Temporal dynamics and controlling factors under semiarid conditions

During decades, in semiarid agroecosystems of the Ebro valley, intensive soil tillage and low crop residue input has led to a loss of soil structure. Conservation tillage and cropping intensification can improve soil structure in these areas. The objective of this study was to determine the influence of three different tillage systems (conventional tillage, CT; reduced tillage, RT; and no-tillage, NT) under two cropping systems (barley–fallow rotation, CF; and continuous barley, CC) on soil aggregation dynamics during two consecutive growing seasons (2003–2004 and 2004–2005). At the same time, the role that different soil and climatic factors play on soil aggregation in these semiarid areas was studied. Soil samples were collected at the soil surface (0–5 cm depth) from a long-term tillage experiment with a loamy soil (Xerollic Calciorthid). Two aggregation indexes were studied: dry aggregate size distribution and water aggregate stability from both air-dried and field-moist macroaggregates. A decrease in tillage intensity resulted in a higher mean size of dry aggregates and a greater water aggregate stability in both cropping systems particularly under NT. During the whole experiment, the dry aggregate size distribution (measured as the mean weight diameter, MWD) and the water stability of field-moist and air-dried soil aggregates (WAS AD and WAS FM, respectively) were greater under NT than under RT and CT due to a higher soil organic matter content under NT. Intensification of cropping system resulted in a greater water aggregate stability (both WAS AD and WAS FM) but it did not have any effect in the MWD. Differences among tillage treatments were more pronounced under the CC system than under the CF rotation due to the lower soil organic matter content and microbial biomass when long-fallowing was used. Variations in soil aggregation dynamics during the cropping season were mainly affected by crop growth and the associated activity of soil microorganisms. These findings indicate that the use of alternative management practices as NT and CC are viable strategies to improve soil aggregation from semiarid Ebro valley.

Influence of two organic amendments on the soil physical properties, soil losses, sediments and runoff water quality

Organic soil amendments are increasingly being examined for their potential use in preventing soil losses. The influence of two organic wastes (cotton gin crushed compost, CC, and poultry manure, PM) applied during a period of four years on a Xerollic Calciorthid under dryland conditions near to Seville (Guadalquivir Valley, Andalusia, Spain) on soil physical properties (structural instability and bulk density), soil loss (at 60 and 140 mm h − 1 , respectively) and nutrient losses (organic carbon, NO 3 −–N, NH 4 +–N, P and K) in runoff water with the intention of observing possible eutrophication risks in waters, and sediments were studied. CC and PM were applied annually at rates of 3560 and 7120 kg organic matter ha − 1 yr − 1 , respectively. Both organic wastes reduce aggregate instability, bulk density and soil loss. In detail and compared with the control soil (no organic treatment), CC and PM at the higher dose reduced aggregate instability by 21% and 17.8%, respectively, bulk density by 19.6% and 16.9%, respectively, and soil loss under simulated rain at 140 mm h − 1 by 29.2% and 25%, respectively. Nutrient losses in the runoff water and sediments were higher in organic-amended soils than in the control soil, particularly in the case of the PM-amended soils. The lower N/P ratios in runoff water produced by CC and PM treatments suggest a lower eutrophication risk in water. The variability in these results may be due to the different chemical natures of the wastes added to soil.

Soil carbon dioxide fluxes following tillage in semiarid Mediterranean agroecosystems

In semiarid Mediterranean agroecosystems, low and erratic annual rainfall together with the widespread use of mouldboard ploughing (conventional tillage, CT), as the main traditional tillage practice, has led to a depletion of soil organic matter (SOM) and with increases in CO 2 emissions from soil to the atmosphere. In this study, we evaluated the viability of conservation tillage: RT, reduced tillage (chisel and cultivator ploughing) and, especially, NT (no-tillage) to reduce short-term (from 0 to 48 h after a tillage operation) and mid-term (from 0 h to several days since tillage operation) tillage-induced CO 2 emissions. The study was conducted in three long-term tillage experiments located at different sites of the Ebro river valley (NE Spain) across a precipitation gradient. Soils were classified as: Fluventic Xerocrept, Typic Xerofluvent and Xerollic Calciorthid. Soil temperature and water content were also measured in order to determine their influence on tillage-induced CO 2 fluxes. The majority of the CO 2 flux measured immediately after tillage ranged from 0.17 to 6 g CO 2 m −2 h −1 and was from 3 to 15 times greater than the flux before tillage operations, except in NT where soil CO 2 flux was low and steady during the whole study period. Mid-term CO 2 emission showed a different trend depending on the time of the year in which tillage was implemented. Microclimatic soil conditions (soil temperature and water content) had little impact on soil CO 2 emission following tillage. In the semiarid Mediterranean agroecosystems studied, NT had low short-term soil CO 2 efflux compared with other soil tillage systems (e.g., conventional and reduced tillage) and therefore can be recommended to better manage C in soil.

Application of different organic amendments in a gasoline contaminated soil: Effect on soil microbial properties

The effects of four organic wastes, including cotton gin crushed compost (CC), poultry manure (PM), sewage sludge (SS) and organic municipal solid waste (MSW) on some biological properties of a Xerollic Calciorthid soil polluted with gasoline at two loading rates (5% and 10%) were studied in an incubation experiment. Three hundred grams of sieved soil (<2 mm) were polluted with gasoline and mixed with PM at a rate of 10%, CC at a rate of 17.2%, SS at a rate of 23.1%, or MSW at a rate of 13.1%, applying to the soil the same amount of organic matter with each organic amendment. An unamended soil, non polluted (C) and polluted with gasoline at 5% (G1) and 10% (G2) rate were used as reference. Soil samples were collected after 1, 30, 60, 90, 120, 180 and 270 d of incubation and analyzed for microbial biomass carbon, respiration and dehydrogenase, urease, β-glucosidase, phosphatase and arylsulfatase activities. At the end of the incubation period, soil biological properties were higher in organic amended soils than in C, G1 and G2 treatments. In particular, soil microbial biomass carbon and dehydrogenase, urease, β-glucosidase, phosphatase and arylsulfatase activities increased 87.1%, 92.9%, 88.7%, 93.2%, 78.2% and 85.3%, respectively for CC-amended soils respect to G2, 85.7%, 82.3%, 87.3%, 92.2%, 76.7% and 83.6%, respectively for PM-amended soils; 82%, 90%, 84.8%, 89.9%, 74.1% and 80%, respectively for SS-amended soils; and 71.3%, 78.3% 26.2%, 38.2%, 79.7% and 88.6%, respectively for MSW-amended soils. Since the adsorption capacity of gasoline was higher in CC than the PM, SS and MSW-amended soils, it can be concluded that the addition of organic wastes with higher humic acid concentration is more beneficial for remediation of soils polluted with gasoline.

Characterizing Soil Water‐Conducting Macro and Mesoporosity as Influenced by Tillage Using Tension Infiltrometry

Knowledge of soil water conductive porosity is of paramount importance for understanding the water and solute movement in soil. The objective of this study was to describe and evaluate an alternative pore index, i.e., the representative mean pore radius for two consecutive soil water tensions (λΔΨ), for characterizing the water‐transmitting macro‐ and mesoporosity of soil. The hydraulic conductivity (K) and related hydraulic parameters were measured using a tension disk infiltrometer at −14, −4, −1, and 0 cm water pressure heads at a soil depth of 2 cm on a long‐term conservation tillage experiment (after 9 yr of trial) under conventional tillage (CT), reduced tillage (RT), and no‐tillage (NT) treatments. The soil was loam (Xerollic Calciorthid). The measurements were performed within the first half of a 16‐ to 18‐mo‐long fallow period. Unlike the model based on the classical capillary rise theory, which assumes no differences between measurement sites (e.g., tillage treatments) for the corresponding equivalent pore radius (C0) for macro‐ and mesopores, significant differences in λΔΨ values for macro‐ and mesopores were found between the three tillage systems tested. The number of water‐transmitting macro‐ and mesopores per unit area estimated by means of the capillary rise approach was significantly greater than that calculated using the λΔΨ pore index. Although significantly higher values of λΔΨ for both macro‐ and mesopores were observed under NT, a significantly lower near‐saturation K was found under NT than CT and RT treatments due to the lower density of water‐transmitting macro‐ and mesopores.

Application of two beet vinasse forms in soil restoration: Effects on soil properties in an arid environment in southern Spain

Abstract Organic soil amendments are being increasingly examined for their potential in soil restoration. Two beet vinasse forms (fresh, BV, and composted with a crushed cotton gin compost, CV) were applied annually for a period of four years to a Xerollic Calciorthid soil located near Seville (Guadalquivir Valley, Andalusia, Spain) in order to evaluate the efficiency of these organic amendments in soil restoration. The effects of these amendments on plant cover, soil's physical (structural stability, bulk density), chemical (exchangeable sodium percentage), and biological properties (microbial biomass, soil respiration and enzymatic activities such as dehydrogenase, urease, BBA-protease, â-glucosidase, phosphatase and arylsulfatase) were determined. Organic wastes were applied at 5, 7.5, and 10 t organic matter ha−1 rates, respectively. After 4 years of successive soil amendment, the percentage of plant cover decreased 58.3% in BV-amended soils whereas increased 86% in CV-amended soils with respect to the unamended soil. The application of fresh beet vinasse had a detrimental impact on the soil's physical (structural stability decreased 25.2% and bulk density increased 22.9% with respect to the control soil), chemical (exchangeable sodium percentage increased 86.9%), and biological properties (microbial biomass, soil respiration, and dehydrogenase, urease, BBA-protease, â-glucosidase, phosphatase and arylsulfatase activities decreased by 44.9%, 26.2%, 17.6%, 14.8%, 11.1%, 5%, 63% and 59.6%, respectively, probably because high quantities of monovalent cations, such as Na+, and fulvic acids were introduced into the soil by the vinasse, thus destabilizing its structure. However, when beet vinasse was co-composted with a cotton gin crushed compost, the resulting compost had a positive effect on the soil's physical (structural stability increased 26.5% and bulk density decreased 26.3% with respect to the control soil), and biological properties (microbial biomass, soil respiration, and dehydrogenase, urease, BBA-protease, â-glucosidase, phosphatase and arylsulfatase activities increased by 57.1%, 76.4%, 98.4%, 98.2%, 99.8%, 99.4%, 89.8% and 92.3%, respectively, with respect to the control soil). While the application of CV protect the soil and will contribute to its restoration, the application of BV deteriorates the soil and therefore does not contribute to its restoration.

Application of Two Organic Amendments on Soil Restoration: Effects on the Soil Biological Properties

One method for recovering degraded soils in semiarid regions is to add organic matter to improve soil characteristics, thereby enhancing biogeochemical nutrient cycling. In this paper, we studied the changes in soil biological properties as a result of adding a crushed cotton gin compost (CCGC) and a poultry manure (PM) for 4 yr to restore a Xerollic Calciorthid located near Seville (Guadalquivir Valley, Andalusia, Spain). Organic wastes were applied at rates of 5, 7.5, and 10 Mg organic matter ha(-1). One year after the assay began, spontaneous vegetation had appeared in the treated plots, particularly in that receiving a high PM and CCGC dose. After 4 yr, the plant cover in these treated plots was around 88 and 79%, respectively, compared with 5% for the control. The effects on soil microbial biomass and six soil enzymatic activities (dehydrogenase, urease, BBA-protease, beta-glucosidase, arylsulfatase, and alkaline phosphatase activities) were ascertained. Both added organic wastes had a positive effect on the biological properties of the soil, although at the end of the experimental period and at high dosage, soil microbial biomass and soil enzyme activities were generally higher in the PM-amended soils compared to the CCGC-amended soils. Enzyme activity from the PM-amended soil was 5, 15, 13, 19, 22, 30, and 6% greater than CCGC-amended soil for soil microbial biomass, urease, BBA-protease, beta-glucosidase, alkaline phosphatase, arylsulfatase, and dehydrogenase activities, respectively. After 4 yr, the percentage of plant cover was > 48% in all treated plots and 5% in the control.

Growth, yield and water use efficiency of winter barley in response to conservation tillage in a semi-arid region of Spain

In the semi-arid areas of Aragón (NE Spain), dryland crop production is limited by low and variable precipitation. Conservation tillage has been proposed as a promising strategy to improve soil and water conservation in these areas. A long-term field research project to determine the feasibility of conservation tillage was initiated in 1989 at four locations, three on loam to silt loam soils (Xerollic Calciorthid) and one on a silty clay loam (Fluventic Ustochrept), receiving between 300 and 600 mm of average annual rainfall. This study compared, under both continuous cropping and cereal-fallow rotation, the effects of conventional tillage (mouldboard plough) and two conservation tillage systems, reduced tillage (chisel plough) and no-tillage, on winter barley ( Hordeum vulgare L.) growth and yield, and water use efficiency during the first two growing seasons. Whereas a similar crop response between the conventional and reduced tillage treatments was generally found at all locations, poor performance with no-tillage was observed at the most arid sites. At these sites, lower early growth of barley with no-tillage resulted in a 53% reduction in grain yield, compared to conventional tillage. This unfavourable crop response to no-tillage was due to a lower crop water use, mainly starting with the stem elongation stage (20% lower than the tilled treatments), and a larger proportion of total water use lost as evaporation (69% compared to 50% of tilled treatments). Values of water use efficiency for grain production (0.7–17.0 kg ha −1 mm −1) and transpiration efficiency (7.4–23.8 kg ha −1 mm −1) were within the ranges reported for cereal crops in Mediterranean environments. Fallowing in the cereal-fallow rotation proved to be an inefficient practice for improving soil water storage and subsequent crop yield, under both conventional and conservation management. Based on the study, we conclude that, up to now, only reduced tillage provides an alternative to conventional tillage to maintain crop production in the dryland cereal-growing areas of Aragón.

PHOSPHORUS STATUS OF CALCAREOUS AND SODIC SOILS TREATED WITH CHEESE WHEY

Acid cheese whey, made using phosphoric acid, contains up to 1200 mg total P kg1 whey, and culturedcheese or sweet wheys contain up to 500 mg total P kg1 whey. Much of the 32 106 m3 of whey produced in the UnitedStates each year is applied to soil. Whey P mobility has not been documented for calcareous or sodic soils. This study wasconducted to determine the ratio between ortho- and the more soluble organic P forms in freshly produced cheese whey,and to determine ortho- and organic P concentrations by depth within calcareous and sodic soils within one to two yearsof different whey rates and time of the year applications. Applications of up to 1050 kg P ha1 in acid whey were appliedto a sodic soil (in green house lysimeters) and up to 750 kg P ha1 in sweet whey were applied to calcareous soils(field plots). Bicarbonate-extractable ortho-P did not move below 0.3 m in the sodic Freedom silt loam (fine-silty, mixed,mesic, Xerollic Calciorthid) soil by the end of one growing season. Neither bicarbonate-extractable nor saturation extractortho- or organic P moved below 0.6 m in the calcareous Portneuf silt loam (coarse-silty, mixed, mesic, DurixerollicCalciorthid) soil after three growing seasons or below 0.3 m in the calcareous Nibley silty clay loam (fine, mixed, mesicAquic Argiustolls) soil after two growing seasons. Even though the wheys contained up to 42% organic P, these soilsretained the applied ortho- and organic P against leaching. The winter-applied whey-P did not move deeper into the soilthan that applied during the growing season.

A comparison between seasonal changes in soil water storage and penetration resistance under conventional and conservation tillage systems in Aragón

Low and extremely variable precipitations limit dryland crop production in the semi-arid areas of Aragón (NE Spain). These areas are also affected by high annual rates of topsoil losses by both wind and water erosion. A long-term experiment to determine the feasibility of conservation tillage in the main winter barley production areas of Aragón was initiated in 1989 at four locations, three on loam to silt loam soils (Xerollic Calciorthid) and one on a silty clay loam (Fluventic Ustochrept), receiving between 300 and 600 mm of average annual rainfall. In this study, we compared, under both continuous cropping and cereal-fallow rotation, the effects of conventional tillage (mouldboard plough) and two conservation tillage systems, reduced tillage (chisel plough) and no-tillage, on soil water content and penetration resistance during the first two growing seasons. Whereas reduced and conventionally tilled treatments generally had similar soil water content during the experimental period, the effects of no-tillage were inconsistent. No-tilled plots had from 26% less to 17% more stored soil water (0–80 cm) than conventional tilled plots at the beginning of the growing season. In contrast to the conventional and reduced tillage treatments, penetration resistances were between 2 and 4 MPa after sowing in most of the plough layer (0–40 cm) under no-tillage at all sites. Fallow efficiencies in moisture storage in the cereal-fallow rotation, when compared with the continuous cropping system, ranged from −8.7 to 12%. The highest efficiencies were recorded when the rainfall in the months close to primary tillage exceeded 100 mm. Since this event is very unlikely, long fallowing (9–10 months) appears to be an inefficient practice for water conservation under both conventional and conservation management. Our results suggest that, up to now, only reduced tillage could replace conventional tillage without adverse effects on soil water content and penetration resistance in the dryland cereal-growing areas of Aragón.

Irrigated Spring Wheat Response to Topdressed Nitrogen as Predicted by Flag Leaf Nitrogen Concentration

Topdressed N is frequently applied to irrigated hard red spring (HRS) wheat (Triticum aestivum L.) in an effort to increase grain protein content (GPC). However, the actual need for supplemental N could be better defined if the probability of a response was referenced to some measure of plant N status. This study was conducted to determine whether flag leaf N (FLN) concentration at heading could be used to estimate the potential for increasing GPC with topdressed N. Field studies were conducted in 1989, 1990, and 1991 on a Declo silt loam (coarse loamy, mixed, mesic Xerollic Calciorthid). Two HRS wheat varieties (Copper and Pondera) received preplant applications of either 0, 60, 120, or 180 lb N/acre to produce a range of FLN concentrations at heading. Plants at each N level were top-dressed with either 0, 20, or 40 lb N/acre 1 to 2 d after heading. Topdressed N had relatively little effect on grain yield or test weight. Flag leaf N concentrations and GPC were both increased by preplant and topdressed N applications, however. Grain protein contents of both varieties were positively correlated with N concentrations of flag leaves sampled prior to N top-dressing. Grain protein content of low N plants (3.0 to 3.6% N) was increased by 1.0 to 1.5% with 20 lb N/acre topdress applications and 2.0 to 2.5% with 40 lb N/acre applications. Increases in GPC resulting from N topdressing decreased linearly as FLN at heading increased. Plants with FLN concentrations above 4.2% did not benefit from topdressed N. Results of this study provide preliminary evidence that FLN concentration can provide a good indication of the likelihood of a response to topdressed N. Research Question Irrigated hard red spring wheat growers are encouraged to split N applications during the growing season to increase grain protein content (GPC) and N-use efficiency. Split N applications could be managed more effectively if there was a predictive tool available to correlate plant N status with the potential for a GPC response to N topdressing. The primary objective of this research was to evaluate flag leaf N (FLN) concentration as a more precise predictor of GPC response to N topdressing. Literature Summary Studies conducted with irrigated and nonirrigated wheat production systems have shown that wheat GPC can be influenced by late split N applications. Responses are especially effective when application is made between heading and flowering. The response becomes limited, however, if plant N status is high. Pacific Northwest wheat growers frequently apply late-season N fertilizer in hopes of obtaining a GPC response. Few studies have been completed which provide growers with information to predict a response to these late N fertilizer applications. Study Description Two irrigated hard red spring wheat cultivars were planted in combination with four preplant and three topdressed-N fertilizer rates in each of 3 yr at Aberdeen, ID. Wheat varieties: Copper and Pondera, 110 lb/acre in 7 in. row Soil: Declo silt loam Fertility: Idaho Soil Test Irrigation: Sprinkler irrigation Weed control: Bromoxynil and MCPA Treatments: N was applied preplant at either 0, 60, 120, or 180 lb N/acre Topdressed N rates of 0, 20, or 40 lb N/acre were applied at heading N fertilizer: Ammonium nitrate (34-0-0) Flag leaf N sampling: Heading (Zadoks 59) and early milk (Zadoks 73) Sample size: 25 flag leaves/plot Applied Question Is FLN concentration at heading a good predictor of GPC response to topdressed N in irrigated hard red spring wheat? When hard red spring wheat plants were topdressed with N at heading, there usually was an increase in GPC. This increase was closely related to FLN concentration at heading. Nitrogen topdressing increased GPC of low N plants (3.0 to 3.6% N) by 1.0 to 2.5%. As FLN at heading increased, the GPC response to topdressed N became progressively smaller. Plants with FLN concentrations above 4.2% generally did not respond to topdressed N. Heading is an appropriate sampling time since topdressed N is often applied during flowering. The relationships between FLN and GPC may differ between locations, soil moisture conditions, and other environmental factors. Therefore, local calibration of FLN relationships with yield and GPC probably will be required for specific production areas. Recommendations We recommend that growers who have a desire to increase GPC with late season N applications use FLN concentrations at heading as an appropriate predictor for response.

Effects of sewage sludge treatments on aggregate slaking, clay dispersion and hydraulic conductivity of a semi-arid soil sample

The semi-arid Zezia soil (fine, mixed, thermic Xerollic Calciorthid) is characterized by an unstable structure. Aggregate stability of sludge-amended samples was evaluated by measuring the optical transmission (%T) of two size fractions ( < 2 μm and < 5 μm) “dispersed” in NaCl/CaCl 2 solutions of decreasing electrolyte concentration at constant SAR values of 5, 10, 15, or 20. In addition, the hydraulic conductivity (HC) of reference and sludge-amended soil columns was measured by permeating similar electrolyte solutions of decreasing concentration at constant SAR of 5, 10, or 20. The sludge-amended samples were prepared by mixing sludge:soil portions (wt/wt) equivalent to 2, 4, and 8%. The moistened mixtures were incubated in the laboratory for 6 months after which the samples were air-dried and ground to pass a 2 mm sieve. For the < 2 and < 5 μm size fractions, %T of the soil suspensions increased linearly with increasing electrolyte concentration beyond a certain limiting value dependent on the solution SAR and sludge application rate. Only the 8% sludge treatment was effective in preventing extensive clay dispersion with decreasing electrolyte concentration at SAR ⩽ 10. The 8% sludge treatment also improved the aggregate stability as indicated by decreasing threshold concentration (corresponding to % T = 20) of the < 5 μm size fraction to levels lower than the respective values of the other sludge-treated samples. At a given SAR, the ratio of the < 5 μm-TC to the < 2 μm-TC was almost constant irrespective of the sludge treatments and, thus, supported the hypothesis that clay dispersion takes place at the ultimate stage of aggregate slaking. At any combination of SAR-electrolyte concentration of the permeating solutions, HCs of the 8% sludge-amended samples were greater than the corresponding values of the other samples. For all soil columns, minimum %T of the effluent solution was observed when permeating distilled water following any SAR solution series. The minimum %T of the distilled water effluent solutions decreased with increasing SAR for a given sludge-amended sample and increased with increasing sludge application rate at constant SAR. The limited clay dispersion in the distilled water effluent solutions indicated that the major cause for reductions in HC (e.g. ∼ 80% for the 8% sludge-amended sample permeated with distilled water following SAR 20 solution series) was aggregate slaking rather than clay dispersion and clogging of the conducting pores by the dispersed clay particles.

Colloidal suspensions of calcium carbonate in soils and their likely significance in the formation of calcic horizons

Evidence is presented to demonstrate that colloidal suspensions of calcium carbonate can be produced in the laboratory from naturally occurring CaCO 3 (Upper Chalk) and from a range of calcic horizons (Typic Hapludalf, southern England; Calcixerollic Xerochrept, southern Iran; and Xerollic Calciorthid, lower Egypt). Calcium carbonate in these calcic horizons and associated k-fabrics is in the form of colloidal-sized platelets. Particle size and ability to remain in colloidal suspension were determined for unground and for “TEMA” ground samples. Particle composition was determined using X-ray diffraction, differential thermal analysis and from X-ray fluorescence spectra (XRF). Particle morphology was obtained using the scanning electron microscope (SEM). The spatial morphological patterns observed in the calcic horizons of the three soils consisted of silt-sized, calcite platelets linked together by discontinuous coatings of both single and aggregated clay-sized, calcite platelets. Thus, as calcium carbonate in the soils was shown to be in colloidal form, the spatial and morphological patterns observed at the submicroscopic scale are attributed to physical transport of colloidal complexes rich in calcium carbonate. On mobilization, these colloidal complexes will be transported through inter-, intra- and transpedal pores by movement of soil water and deposited on ped surfaces and as linings to pore walls. Transport of colloidal calcium carbonate and deposition from suspension onto ped and pore surfaces is considered to be enhanced by irrigation practices and by lateral throughflow of water, that is by periodic and discrete soil/water/gravity events.

Nitrogen transformations in calcareous soils amended with pig slurry under aerobic incubation

SUMMARYThe mineralization and nitrification processes in pig slurry were investigated in Spain in 1990 in three calcareous soils, differing mainly in content and type of clay, two classified as Typic Calciorthids and one as a Xerollic Calciorthid. Two different amounts of slurry were mixed with the soils, one equivalent to 273 mg N/kg soil and the other equivalent to 546 mg N/kg soil. The mixtures of soil and slurry were aerobically incubated for 16 weeks at 28 °C. A mean initial immobilization of 22·19% of the total-N added was detected in soils treated with the lower rate of slurry. The amount of mineralized N after 112 days of incubation was between 36 and 47% of the total-N added with the lower slurry application to the three soils. The net amount of N mineralized throughout the experiment was therefore within the range 14–23% of the total-N added. The nitrification of the NH4-N added to the soil began after 7 days of incubation, and followed a first-order kinetic model. The mean values of potential nitrate formation were 61 and 51% of the total-N added in soils amended with 273 and 546 mg N as pig slurry per kg soil respectively. The rate constants were higher in the treatments with the lower slurry application (0·043–0·083 per day). Therefore, in these treatments, the nitrification process was faster and total nitrate levels were higher than in soils receiving double that amount of slurry. The NO3-N evolution was parallel to the total-N evolution from the 14th day of incubation onwards. The N-mineralization process was limited by the transformation of the organic-N into ammonium (ammonification).

Coefficients for estimating SAR from soil pH and EC data and calculating pH from SAR and EC values in salinity models

Abstract Data from highly weathered, low pH, sodic Australian soils have been used to develop a method for estimating soil exchangeable sodium percentage (ESP) or soil extract sodium adsorption ratio (SAR) from soil pH and electrical conductivity (EC) data. The method can also be used to calculate soil pH in soil salinity models using SAR and EC values. The pH was calculated as pH = A + (B × SAR1/2)/(1 + C × EC). Rewriting the equations in terms of SAR (or ESP), gives SAR (or ESP)= [(pH ‐ A)(1 + C × EC)/B]2. This study was conducted to determine whether these same methods could be used to predict the pH and SAR values for arid climate soils that are only slightly weathered and are often sodic under natural conditions. Existing pH, EC, and SAR data from Declo loam (coarse‐loamy, mixed, mesic, Xerollic Calciorthids), Freedom silt loam (fine‐silty, mixed, mesic, Xerollic Calciorthids), and Mazuma sandy loam (coarse‐loamy, mixed (calcareous), mesic Typic Torriorthents) were used to calculate the A, B, and C coefficients for the three high sodium soils. Coefficients obtained for a particular soil site were then used to predict pH or SAR of soil samples at additional sites and the correlation between calculated and measured values were determined. The A values for the Idaho soils are about 0.8 greater than those for the Australian soils, which were not completely base saturated. The Australian soils B values were about twice that of the calcareous Idaho soils, and the C values were not significantly different for the Australian and Idaho soils. In both cases the A coefficient values were slightly smaller than or nearly equal to the smallest pH values in a particular data set. Using coefficients from one location of a particular sodic or saline‐sodic soil to predict pH or SAR of the same soil, at a second location, was shown to be practical. Each soil type, however, requires its own set of coefficients. These relationships provide a rapid field method for estimating SAR or ESP from easily obtainable EC and pH data once the A, B, and C coefficients are determined for a particular soil. They also provide a method for pH calculation in soil salinity models that take into account soil EC and sodium effects on pH.

Cottage cheese (acid) whey effects on sodic soil aggregate stability

Whey applications reduce a sodic soil's exchangeable sodium percentage (ESP) and sodium adsorption ratio (SAR) and increase its infiltration rate. Whey's effects on aggregate stability (AS), however, have been less well documented. A greenhouse study was conducted to determine: (1) AS response to whey additions, (2) the profile depth to which surface‐applied whey affected AS, and (3) the relationship between AS and SAR for an illitic soil. Greenhouse lysimeters packed with a Freedom silt loam (Xerollic Calciorthid,) received either 0, 25, 50, or 100 mm of whey (equivalent to 0, 253, 505, and 1010 Mg ha‐1 of liquid whey). After drying, the surface 150 mm was removed, mixed, and replaced. Barley (Hordeum vulgae L. ‘Ludd') was then planted and grown to maturity by irrigating weekly. After harvest, AS was measured by wet sieving. A companion field study was conducted to determine the effects of whey applications and flood irrigations on AS. In Declo silt loam (Xerollic Calciorthid,), 2 X 2 m basins received 0...