Soil Total P Research Articles

PERBAIKAN PRODUKSI TANAMAN JAGUNG PADA ULTISOL MENGGUNAKAN ABU TERBANG BATUBARA DAN KOMPOS TANDAN KOSONG KELAPA SAWIT

The potential of Ultisols, especially in East Kalimantan for the development of food crop agriculture is faced with constraints on phosphorus availability due to low soil pH and high solubility of aluminum (Al). The purpose of this study was to elucidate the effect of a combination application of coal fly ash (CFA) and oil palm empty fruit bunches (OPEFB) on the availability of phosphorus in an Ultisol from East Kalimantan and its impact on the production of maize. The combination of CFA and OPEFB consisted of seven treatments with three replications. The research was carried out in two steps. The first experiment (incubation in the laboratory), was carried out under non-leaching condition for 42 days. Parameters observed included soil pH, available soil P, total soil P, and soil exchangeable Al. The second experiment (growth experiments in a glasshouse), was were carried out by growing maize plants with the same treatment as for experiment 1. The plant height and leaf area were observed every week. At the harvest time (age 12 weeks), dry weight of shoots and roots, maize weight with cobs, and maize weight without cobs were observed. The results of soil incubation showed the decrease in the soil exchangeable Al- level, the increase in soil total-P, and soil available-P. The combination application of CFA and OPEFB did not have a significant impact on soil pH, and soil organic-C. The results of the glasshouse experiment showed that CFA and OPEFB were not significantly different in the parameters of plant height, leaf area of 12 weeks, weight of shoots and roots, maize weight with cobs, and maize weight without cobs.

Spatial variations in soil phosphorus along a gradient of central city-suburb-exurban satellite

Urbanization has progressively intensified over the past few decades, transforming the structure and function of urban ecosystems and influencing the concentrations and spatial distributions of phosphorus (P) in the soil. This study collected 177 surface soil samples (to a depth of 20 cm) to understand the dynamics of soil P along a gradient of urbanization from a densely urbanized central city to less human-affected suburbs to a new exurban satellite in Chengdu, China. The results showed that concentrations of soil total P (TP) and its fractions (except Water-Po, NaOH-Pi, and Residual-P) in the central city and exurban satellite were significantly higher than in suburban areas (p < 0.05). Meanwhile, the concentrations of soil TP and its fractions (except Residual-P) significantly decreased with the increase in distance from the urban center (p < 0.05). These concentrations were significantly positively correlated with the densities of built-up areas and roads, and showed significant differences among different green space types. The results of generalized linear models indicated that the most decisive factors contributing to TP accumulation were the distance from urban center and green space type. Generally, green space type and density of built-up area were likely to be more crucial determinants governing soil inorganic P fractions compared with other factors, whereas the key factors affecting soil organic P fractions were varied. To conclude, urbanization is likely to lead to the accumulation of P and, thus, controlling the expansion of built-up areas and road areas is necessary to alleviate soil P accumulation in urban systems.

Phosphorus efficiency, soil phosphorus dynamics and critical phosphorus level under long-term fertilization for single and double cropping systems

Wise phosphorus (P) management is paramount to ensure food and environmental security and prolong the life of P resources. Long-term experiments under winter wheat–summer maize (with irrigation) and winter wheat–summer fallow (rain-fed) cropping systems were undertaken to investigate P efficiency, soil P availability and P downward movement in the deep profile of a loess soil in China. The four nutrient management regimes in each experiment were: a control without any nutrient input; P and K combined (PK); N, P and K combined (NPK), and organic manure (M) combined with NPK (MNPK). The P efficiency ranged from 20 to 54% under the double cropping system, and from 13 to 33% in the single cropping system over the 25 years studied, and the highest P efficiency was in the NPK treatment in both systems. Application of P significantly increased soil total-P, Olsen-P and CaCl2-P over the years, especially in the MNPK treatment. Two segment regression analyses indicated that Olsen-P was about 14 mg kg−1 or 16 mg kg−1 for optimal crop yield under double cropping or single cropping. In addition, Olsen-P content above 37 mg kg−1 or 57 mg kg−1 led to a significant increase in CaCl2-P content under double cropping or single cropping, which might indicate risk of P leaching. After 24 years of P applications, total P accumulated at various depths depending on treatment under double cropping, but there was no accumulation under single cropping. While Olsen-P leached down to a depth of 300 cm in the MNPK treatments under both cropping systems, and higher concentrations were recorded in the deeper layers in single cropping than in double cropping systems. The Olsen-P leached to a shallower depth in the PK and NPK treatments under single cropping compared to double cropping. We conclude that P supply in excess of the crop’s requirement (e.g. MNPK) or an unbalanced nutrient supply (e.g. PK) resulted in not only low P efficiency and massive accumulation of P in the topsoil but also leaching out of root zone under both irrigated and rain-fed conditions in the loess soil. Thus, P fertilization recommendations need to be adjusted based on changes in soil P over time.

Drainage water management combined with cover crop enhances reduction of soil phosphorus loss

Integrating multiple practices for mitigation of phosphorus (P) loss from soils may enhance the reduction efficiency, but this has not been studied as much as individual ones. A four-year study was conducted to determine the effects of cover crop (CC) (CC vs. no CC, NCC) and drainage water management (DWM) (controlled drainage with sub-irrigation, CDS, vs. regular free tile drainage, RFD) and their interaction on P loss through both surface runoff (SR) and tile drainage (TD) water in a clay loam soil of the Lake Erie region. Cover crop reduced SR flow volume by 32% relative to NCC, regardless of DWM treatment. In contrast, CC increased TD flow volume by 57 and 9.4% with CDS and RFD, respectively, compared to the corresponding DWM treatment with NCC. The total (SR+TD) field water discharge volumes were comparable amongst all the treatments. Cover crop reduced flow-weighted mean (FWM) concentrations of particulate P (PP) by 26% and total P (TP) by 12% in SR, while it didn't affect the FWM dissolved reactive P (DRP) concentration, regardless of DWM treatments. Compared with RFD, CDS reduced FWM DRP concentration in TD water by 19%, while CC reduced FWM PP and TP concentrations in TD by 21 and 17%, respectively. Total (SR+TD) soil TP loss was the least with CDS-CC followed by RFD-CC, CDS-NCC, and RFD-NCC. Compared with RFD-NCC, currently popular practice in the region, total TP loss was reduced by 23% with CDS-CC. The CDS-CC system can be an effective practice to ultimately mitigate soil P loading to water resource.

Soil phosphorus dynamic, balance and critical P values in long-term fertilization experiment in Taihu Lake region, China

Phosphorus (P) is an important macronutrient for plant but can also cause potential environmental risk. In this paper, we studied the long-term fertilizer experiment (started 1980) to assess the soil P dynamic, balance, critical P value and the crop yield response in Taihu Lake region, China. To avoid the effect of nitrogen (N) and potassium (K), only the following treatments were chosen for subsequent discussion, including: C0 (control treatment without any fertilizer or organic manure), CNK treatment (mineral N and K only), CNPK (balanced fertilization with mineral N, P and K), MNK (integrated organic manure and mineral N and K), and MNPK (organic manure plus balanced fertilization). The results revealed that the response of wheat yield was more sensitive than rice, and no significant differences of crop yield had been detected among MNK, CNPK and MNPK until 2013. Dynamic and balance of soil total P (TP) and Olsen-P showed soil TP pool was enlarged significantly over consistent fertilization. However, the diminishing marginal utility of soil Olsen-P was also found, indicating that high-level P application in the present condition could not increase soil Olsen-P contents anymore. Linear-linear and Mitscherlich models were used to estimate the critical value of Olsen-P for crops. The average critical P value for rice and wheat was 3.40 and 4.08 mg kg−1, respectively. The smaller critical P value than in uplands indicated a stronger ability of P supply for crops in this paddy soil. We concluded that no more mineral P should be applied in rice-wheat system in Taihu Lake region if soil Olsen-P is higher than the critical P value. The agricultural technique and management referring to activate the plant-available P pool are also considerable, such as integrated use of low-P organic manure with mineral N and K.

Soil phosphorus composition and phosphatase activities along altitudes of alpine tundra in Changbai Mountains, China

Alpine tundra ecosystems have specific vegetation and environmental conditions that may affect soil phosphorus (P) compo- sition and phosphatase activities. However, these effects are poorly understood. This study used NaOH-EDTA extraction and solution 31 P nuclear magnetic resonance (NMR) spectroscopy to determine soil P composition and phosphatase activities, including acid phos- phomonoesterase (AcP), phosphodiesterase (PD) and inorganic pyrophosphatase (IPP), in the alpine tundra of the Changbai Mountains at seven different altitudinal gradients (i.e., 2000 m, 2100 m, 2200 m, 2300 m, 2400 m, 2500 m, and 2600 m). The results show that total P (TP), organic P (OP), OP/TP, NaOH-EDTA extracted P and AcP, PD, and IPP activities over the altitude range of 2500-2600 m are significantly lower than those below 2400 m. The dominant extracted form of P is OP (73%-83%) with a large proportion of monoesters (65%-72%), whereas inorganic P is present in lower proportions (17%-27%). The activity of AcP is significantly positively correlated with the contents of soil OP, total carbon (TC), total nitrogen (TN), and TP (P < 0.05), indicating that the AcP is a more sensitive index for responding P nutrient storage than PD and IPP. Soil properties, P composition, and phosphatase activities decrease with increased altitude and soil pH. Our results indicate that the distribution of soil P composition and phosphatase activities along altitude and AcP may play an important role in P hydrolysis as well as have the potential to be an indicator of soil quality.

闽江河口湿地土壤全磷高光谱遥感估算

PDF HTML阅读 XML下载 导出引用 引用提醒 闽江河口湿地土壤全磷高光谱遥感估算 DOI: 10.5846/stxb201406241303 作者: 作者单位: 1.福建师范大学亚热带湿地研究中心,1.福建师范大学亚热带湿地研究中心,1.福建师范大学亚热带湿地研究中心,1.福建师范大学地理科学学院,1.福建师范大学地理科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家基础科学人才培养基金(J1210067) Estimating the soil total phosphorus content based on hyper-spectral remote sensing data in the Min River estuarine wetland Author: Affiliation: 1 Research Center of Wetlands in Subtropical Region,1 Research Center of Wetlands in Subtropical Region,1 Research Center of Wetlands in Subtropical Region,1 School of geographical sciences,1 School of geographical sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:磷是湿地生态系统必需和限制性元素,利用高光谱遥感数据对其进行估算对实现湿地土壤磷素快速和准确定量具有重要意义。选取闽江河口湿地作为研究区,于2013年5月,采集16个土壤剖面80个样本作为估算与验证模型样本;基于光谱指数建立土壤全磷(TP)含量估算模型,其中光谱指数包括原始光谱反射率(R)、比值土壤指数(RSI)、归一化土壤指数(NDSI)和有机质诊断指数(OII)。此外,进一步分析反射光谱与不同形态磷,TP与有机质之间关系,以期初步揭示河口湿地土壤TP估算的机理。研究结果表明,闽江河口湿地土壤TP含量与R相关系数较高的区域分布在360-560 nm,并在406 nm处达到最大值-0.816;光谱指数RSI(R430, R830)、RSI(R460, R810)、RSI(R560, R580)、NDSI(R430, R830)、NDSI(R460, R830)、NDSI(R560, R580)和OII(R446)与土壤TP含量均有较高的相关系数,能较好的用于TP含量的估算;各估算模型决定系数(r2)和均方根误差(RMSE)分别在0.657-0.805和0.052-0.067之间;验证模型r2和RMSE分别在0.606-0.893和0.037-0.044之间。分潮滩建立TP含量估算模型是可行的,并且能提高部分光谱指数的估算精度。土壤TP含量的估算精度与磷素的组成有关,其中与铁吸附态磷关系较为密切,钙吸附态和铝吸附态磷关系较弱。土壤TP与有机质和氧化还原环境的存在密切关系可能是湿地土壤TP含量估算的重要机理。 Abstract:Phosphorus (P) is an essential and limiting nutrient in wetland ecosystems and it plays a vital role in eutrophication. Remote sensing (RS) offers an up-to-date and relatively accurate means to measure the soil P content. Recently, some studies have shown that it was feasible to estimate the total P (TP) content of terrestrial ecosystem soil based on hyper-spectral RS data. However, little information is available on TP content estimation by RS technology on wetland soil. The aim of this study was to estimate the TP content of wetland soil using hyper-spectral RS data. Min river estuarine wetland, located in the subtropical zone, is one of the most typical and important estuarine wetlands in southeast China. Soil samples, from Shanyutan tidal marsh in the Min River Estuary, were collected in sixteen profiles at five depths (0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, and 40-50 cm) along an elevation gradient, in May of 2013. Estimation and validation models were constructed by spectrum parameters, including original spectral reflectance (R), simple ratio soil index (RSI), normalized difference soil index (NDSI), and organic matter diagnosis index (OII) calculated by optimal bands. The results indicated that the spectral reflectance of the soil increased with depth at 350-580 nm, while an opposite trend was observed at 580-2500 nm. Soil TP content showed a negative correlation with R at 350-600 nm, whereas a positive correlation was observed at 600-2500 nm. The highest correlation coefficient value was -0.816 and occurred at 406 nm. The correlation coefficient between soil TP content and OII exhibited a bimodal distribution, with peaks at 446 nm (r = -0.843) and 634 nm (r = 0.798). NDSI and RSI were each calculated by bands in three zones, (420-440 nm and 440-590 nm, 460-470 nm and 590-1000 nm, and 550-590 nm and 550-590 nm, respectively), which had higher correlation coefficients with TP content than those in other zones. The determination coefficient (r2) and root means square error (RMSE) of estimation models ranged from 0.657-0.805 and 0.052-0.067, respectively, and those of the validation models ranged from 0.606-0.893 and 0.037-0.044, respectively. These results indicate that TP content of the Min River estuarine soil could be estimated by most of the selected parameters. The evaluation parameters of the estimation models supported that estimating the TP content of high and middle tidal flats soil individually could improve the estimation accuracy of some parameters such as RSI(R430, R830), RSI(R460, R810), and NDSI(R430, R830). Additionally, the estimation accuracy of soil TP content also depended on the P fractions. Iron bound phosphorus (Fe-P), occluded phosphorus (O-P), and organic phosphorus (Org P) had higher correlation coefficients with R than did aluminum bound phosphorus (Al-P) and calcium bound phosphorus (Ca-P). The corresponding changes in the contents of TP within organic matter and a redox environment in wetland soil could be used as important mechanisms for estimating soil TP content. In conclusion, it was feasible to estimate TP content of subtropical estuarine wetland soils based on hyper-spectral RS data. 参考文献 相似文献 引证文献

Effects of fertilization regimes on tea yields, soil fertility, and soil microbial diversity

Fertilization is an important agricultural practice for increasing crop yields and influencing soil properties. A field experiment was conducted in the period of 2006-2011 in southeastern China, to investigate the effects of fertilization regimes on tea (Camellia sinensis [L.] Kuntze) yields, soil chemical properties, and soil bacterial and fungal communities. The field experiment included six treatments: (1) unfertilized control (CON); (2) chemical fertilizers (NPK); (3) half-chemical fertilizers plus half-organic manure (1/2NPKOM); (4) organic manure fertilizers (OM); (5) half-chemical fertilizers plus half-organic manure plus legume stover returned (1/2NPKOM+L), and (6) chemical fertilizers plus legume stover returned (NPKL). Results showed that, compared to the control, NPK treatment showed no significant effect on soil organic matter (SOM), total N (TN), total P (TP), total K (TK), available N (AN), available K (AK) and tea yields, but showed the lowest bacterial Shannon index of 1.714 and the lowest value of 2.002 for fungal Shannon index. Organic manure treatment had the richest diversity of soil bacterial community with Shannon index of 2.542, and the highest levels of soil essential nutrients, including SOM (30.03%), TN (2.90 g kg-1), TP (1.35 g kg-1), AN (245.30 mg kg-1), AP (57.00 mg kg-1), and AK (271.80 mg kg-1), followed by 1/2NPKOM+L, which appeared the maximal tea yields of 6772 kg ha-1. Organic manure amendment was a key factor in determining soil properties and productivity. Base on soil quality and tea yields, both OM and 1/2NPKOM+L treatments were recommended as better choices of fertilization practices for tea soils in southeastern China. These findings provided a better understanding of the importance of fertilizations in promoting soil fertility, crop yields, and altering soil microbial diversity, leading to selection of scientific fertilization practices for sustainable development of agroecosystems.

Using manure from cattle fed dried distillers’ grains with solubles (DDGS) as fertilizer: Effects on nutrient accumulation in soil and uptake by barley

Dried distillers’ grain with solubles (DDGS) is becoming a valuable livestock feed with implications for manure composition. This study investigated nutrient uptake by barley (Hordeum vulgare) forage in a growth chamber and accumulation in soil amended with two manure types: from DDGS-fed cattle (DDGS) or grain-fed cattle (REG) at 0, 30, 60, 120 and 180Mgha−1yr−1. There was also a commercial fertilizer (FERT) and un-amended control (Check). Barley was grown and harvested six-times successively from soil receiving either one-time or six-repeated amendment applications over 297-d. Regardless of application regime, soil N, Ca, K and Mg contents in DDGS were similar to those in REG. Soil total-P (TP) and available-P (AP) contents were higher (p<0.05) in DDGS (except for <60Mg DDGS manure ha−1yr−1 at one-time application for TP) than REG, Check and FERT. Barley N and P removal from DDGS were 1.3 and 2.3 times those from REG and 1.8 and 11.8 times those from Check. Although higher (p<0.05) barley yields were observed in DDGS than REG and Check, including DDGS in cattle rations may require increasing land area for manure application due to its higher TP content which poses a risk of P environmental pollution.

Management scenario evaluation for a large treatment wetland using a spatio-temporal phosphorus transport and cycling model

This paper describes the development of a two-dimensional, spatially distributed model to simulate coupled hydrologic and phosphorus (P) biogeochemical processes in a 147-ha cell of a 1544-ha stormwater treatment wetland designed to help protect the greater Everglades, FL, USA. The model was used to assess the effects of a suite of feasible management alternatives on the long-term ability of the wetland to sustain total P (TP) removal. The spatial and temporal dynamics of TP retention were simulated under historical (1995–2000) conditions, and under assumptions of removal of short-circuiting channels and ditches, changes in external hydraulic and TP loading, and long-term (>20 years) impacts on soil and water column TP dynamics under current and reduced load conditions. Internal hydrology and transport processes were calibrated against measured tracer concentrations, and subsequently validated against outflow discharge and spatial chloride concentration data. Cycling of P was simulated as first-order uptake and release, with different uptake coefficients for open water/sparse submerged aquatic vegetation (SAV) areas (0.2 day −1) and dense SAV areas (0.4 day −1), and a much lower, uniform release coefficient (1.97 × 10 −4 day −1). The calibration and validation of the P model showed good agreement with field measurements of water column TP concentrations measured at the wetland outlet (calibration RMSE = 10.5 μg L −1; validation RMSE = 15.6 μg L −1). Under simulated conditions of preferential channels eliminated, average annual TP treatment effectiveness increased by 25%. When inflow TP loads were assumed to be eliminated after 6 years of loading, the release of accumulated soil P sustained predicted annual average outlet concentrations above 6.7 μg L −1 for 18 years, decreasing at a rate of 0.16 μg L −1 yr −1. Sensitivity analyses indicate that the most critical model input factors include flow resistance parameters, initial soil TP content, and P cycling parameters compared to initial water level, initial TP concentration in water column, ET and transport parameters.

Soil organic phosphorus fraction in pine–oak forest stands in Northeastern Germany

Pines ( Pinus sylvestris L.) have been widely used for monoculture forest stands in north-eastern Germany. However, several studies have discussed the need to convert monoculture into mixed forest stands such as pine–oak forest. In this study, we evaluated the impact of 102 years-old pine ( P. sylvestris L.) in monoculture and mixed forest stands of P. sylvestris + Quercus petraea (Matt.) Liebl. of different ages (10, 35, 106 and 124 years-old) on the dynamics of soil organic phosphorus (Po) pools. The study was carried out in the Northern German Lowlands of Brandenburg. Soil samples were taken from forest floor and two mineral soil layers at the depths of 0–10 and 10–20 cm. Different P forms of the sandy soil were obtained by sequential P fractionation, using acid and alkaline extractants. The soil total P (STP) ranged from 100 to 183 mg kg − 1 whereas total organic P (TPo) ranged from 77 to 148 mg kg − 1 . STP was higher in mixed forest stand than in monoculture and decreased with soil depth. The TPo and labile-P in both soil layers increased significantly with increase in age of oak trees. In addition, TPo content was lower in mineral soil compared to the forest floor and accounted for more than 50% of soil total P in the forest stands. The most available-P fraction–labile-P predominated in the oldest pine–oak forest stand (P + O124), accounting for 29% of STP at the 0–10 cm soil depth. The largest P fraction comprised NaOH–Po and represent 62% of STP. Results showed that forest transformation from pure pine monoculture forest into pine-oak mixed forest stands promoted an increase in the TPo and P available. Furthermore, the forms of labile available P increased with age of oak trees, which are capable of maintaining larger fractions of available P under mixed forest stands.

Seasonal variations in phosphorus fractions in semiarid sandy soils under different vegetation types

We investigated the seasonal patterns of soil phosphorus (P) fractions under five vegetation types – Ulmus macrocarpa savanna, grassland, Pinus sylvestris var. mongolica plantation, Pinus tabulaeformis plantation, and Populus simonii plantation – in the southeastern Keerqin Sandy Lands of China. The measured P fractions (0–20 cm depth) included: soil total P (TP), total organic and inorganic P (TPo and TPi), bicarbonate extractable organic and inorganic P (BPo and BPi), microbial biomass P (MBP), and in situ resin-adsorbed P (resin-P). Soil TP and TPo concentrations in the savanna and grassland were significantly lower in summer than in spring and autumn. However, they were relatively stable in three forest plantations. Soil labile P fractions showed a significant seasonal pattern under all vegetation types with the peak in summer, except soil MBP that was constant in the savanna and grassland and BPo that decreased over time in the savanna. This pattern of labile P fractions was attributed to a combination of seasonal climatic changes, low P availability, as well as the biological controls of soil P transformation in the study area. Litter decomposition played a key role in soil P availability. The monthly resin-P released from litter decomposition in summer was 2.6–7.4 times greater than in other seasons, and was 1.7–3.4 times of that in the 10 cm depth soil. Concentrations of soil P fractions were obviously affected by vegetation type. The savanna had the highest total P and MBP concentrations and the P. tabulaeformis plantation had the highest BPi and resin-P among all vegetation types. Among forest plantations, P. simonii plantation had the highest total P and MBP. These results suggest that U. macrocarpa savanna is the best system conserving soil nutrient (particularly P) stocks and microbial activity, followed by the grassland and P. simonii plantation, while the pine plantations are the worst.

Rate of soil recovery following termination of long-term cattle manure applications

Livestock manure application increases soil nutrient levels, enhancing their bioavailability, but potentially increasing environmental concerns. This study investigates the residual effects of long-term cattle feedlot manure applications to continuously cropped fields under semi-arid conditions on soil properties, crop yields and rate of soil recovery after manure application ceases. Solid cattle feedlot manure was applied to a Dark Brown Chernozemic clay loam at 0, 30, 60 and 90 Mg ha − 1 yr − 1 under rain-fed and 0, 60, 120 and 180 Mg ha − 1 yr − 1 under irrigated conditions annually for 14 years (1973–1986) followed by 16 years with no further manure application (1987–2003). Soil samples to 1.5 m were taken and analyzed. Soil organic matter (OM), total nitrogen (TN), NO 3 −, total P (TP), soil test P (STP), and electrical conductivity (EC) levels remained significantly higher in previously manured treatments than in the Control 16 years after manure application ceased. The average grain yields were similar to the Control while straw yields in irrigated treatments were higher than values for the Control over the 16 years following the last manure application. Based on a three-parameter exponential decay ( y = y s + a ⁎ e − bx ) model, the estimated recovery time for soil to return to the pre-manure treatment state increased with the previous manure application rate and was shorter under irrigation. For soil TN, TP and STP, estimated recovery time ranged from 17 to 99 years for surface soil and 0 to 157 years for the 15 to 30 cm depth, while soil NO 3 − and EC in the soil profile (0 to 150 cm) requires 182 to 297 years under rain-fed and 24 to 52 years under irrigated conditions. Thus, long lasting N and P enrichment, from excessive long-term cattle manure applications could pose environmental threats long after application ceases.

Temporal trajectories of phosphorus and pedo-patterns mapped in Water Conservation Area 2, Everglades, Florida, USA

Documenting local change of soil properties over longer periods of time is critical to assess trends along trajectories. We present two types of temporal trajectories that document change in soil phosphorus (P) and pedo-patterns in Water Conservation Area 2, a subtropical wetland in the Everglades, Florida. Our specific objectives were to (i) quantify the spatial distribution of total P (TP) in floc and topsoil at two time periods (1998 and 2003), (ii) create TP change maps using a crisp, geospatial mapping approach, (iii) analyze relationships between floc/soil TP temporal trajectories and vegetation, and (iv) describe change in pedo-patterns using fuzzy sets to account for the uncertainty inherent in crisp soil property mapping. The median TP in floc was 730 mg kg − 1 in 1998 and increased to a median of 751 mg kg − 1 in 2003; whereas the median in soil was 485 mg kg − 1 in 1998 that decreased to 433 mg kg − 1 in 2003. Floc TP change trajectories varied between 0–990 mg kg − 1 (increase) and 0–2900 mg kg − 1 (decrease); and soil TP change trajectories varied between 0–370 mg kg − 1 (increase) and 0–1439 mg kg − 1 (decrease). Phosphorus-enriched sites were associated with nutrient influx via surface waters and showed linkages to expanding Typha domengensis vegetation. The temporal trajectories of pedo-patterns provided pixel-specific signatures of ecosystem processes such as P enrichment, organic matter turnover, hydrologic shifts, and fire in form of fuzzy membership values. The fuzzy set-based temporal trajectory maps provided a holistic approach documenting shifts in this ecosystem due to external environmental drivers and biogeochemical processes within a 5-year period.

Total phosphorus concentrations and compaction in riparian areas under different riparian land-uses of Iowa

Reducing non-point source phosphorus (P) pollution is often necessary to improve water quality in agricultural streams. Soil total P (TP) concentrations and compaction are soil characteristics that can influence P losses to streams. The objective of this study was to compare these two soil characteristics among riparian forest buffers, grass filters, pastures with cattle fenced out of the stream, intensive rotational, rotational and continuously grazed pastures and row-cropped fields in three physiographic regions of Iowa. Soil TP and compaction for the seven riparian land-uses were determined in stream bank and surface riparian soils. Total P concentrations in stream bed material along the seven riparian land-uses were also measured. Total P concentrations in riparian stream bank soils among land-uses ranged from 303 to 398 mg kg −1 in the central region, to 432–518 mg kg −1 in the northeast, to 360–555 mg kg −1 in the southeast. In the surface riparian soils TP among land-uses ranged from 434 to 649 mg kg −1 in the central region, to 493–764 mg kg −1 in the northeast region, to 428–716 mg kg −1 in the southeast region. Finally, the TP concentrations in the stream bed sediments among land-uses ranged 194–307 mg kg −1 in the central region, to 169–461 mg kg −1 in the northeast, to 389–964 mg kg −1 in the southeast. Few soil TP significant differences among riparian land-uses within regions were found. Soil compaction under some of the grazing practices was significantly higher than under the conservation practices. Limited differences in soil TP concentrations and compaction were partially due to the young age of the conservation practices and the rotational and intensive rotational pastures. Past land-use on these sites had been either continuous grazing or row-cropping and those uses were still influencing these soil parameters. Within riparian land-uses, surface riparian soils generally had higher TP than the stream bank riparian soils. Stream bed samples had lower TP concentrations than the riparian soils in the northeast and central regions but were higher than the riparian soils in some of the land-uses in the southeast region. Overall TP concentrations in the stream bank, surface riparian soils and stream bed material were high indicating that these areas can potentially be important source areas of P and the focus should be on reducing the transport of P.

Seasonal changes in herbage production and soil phosphorus contents in Japanese lawngrass (Zoysia japonica Steud.) and tall fescue (Festuca arundinacea Schreb.) pastures

AbstractSeasonal changes in the above‐ground phosphorus (P), soil total P (TP), soil Olsen P (OP) and soil microbial biomass P (MBP) were investigated for 2 years in Japanese lawngrass (Zy) and tall fescue (Tf) pastures on Japanese Andosol, with the goal of clarifying P characteristics in the Zy pasture in comparison with the Tf pasture. The soil P attributes were measured in two soil layers (root mat layer, 0–2.5 cm depth; under layer, 5–10 cm depth). The P concentration of the above‐ground herbage in the Zy pasture, which was higher than the standard value and similar to those in the Tf pasture, might have contributed to the large amounts of the above‐ground P mass. The lack of plowing management and the coverage with Japanese lawngrass might have changed soil TP. The TP, the OP and the OP/TP in the Zy pasture were higher than those in the Tf pasture, and the TP, the OP and the OP/TP at the root mat layer were higher than those at the under layer. A large amount of the TP and high P availability in the soil caused the large amounts of OP. Soil pH, soil microorganisms and MBP might have affected soil P availability in the Zy pasture. Plant litter in the root mat layer of the Zy pasture may have increased soil P accumulation and its availability, which might be reasons for the high P uptake in the present study. Japanese lawngrass pasture may be a system with improved soil P utilization efficiency based on P cycling.

Fractionation and mobility of phosphorus in a sandy forest soil amended with biosolids

Biosolids, i.e., treated sewage sludge, are commonly used as a fertilizer and amendment to improve soil productivity. Application of biosolids to meet the nitrogen (N) requirements of crops can lead to accumulation of phosphorus (P) in soils, which may result in P loss to water bodies. Since 1996, biosolids have been applied to a Pinus radiata D. Don plantation near Nelson City, New Zealand, in an N-deficient sandy soil. To investigate sustainability of the biosolids application programme, a long-term research trial was established in 1997, and biosolids were applied every three years, at three application rates, including control (no biosolids), standard and high treatments, based on total N loading. The objective of this study was to evaluate the effect of repeated application of biosolids on P mobility in the sandy soil. Soil samples were collected in August 2004 from the trial site at depths of 0-10, 10-25, 25-50, 50-75, and 75-100 cm. The soil samples were analysed for total P (TP), plant-available P (Olsen P and Mehlich 3 P), and various P fractions (water-soluble, bioavailable, Fe and Al-bound, Ca-bound, and residual) using a sequential P fractionation procedure. Soil TP and Olsen P in the high biosolids treatment (equivalent to 600 kg N ha(-1) applied every three years) had increased significantly (P<0.05) in both 0-10 cm and 10-25 cm layers. Mehlich 3 P in soil of the high treatment had increased significantly only at 0-10 cm. Olsen P appeared to be more sensitive than Mehlich 3 P as an indicator of P movement in a soil profile. Phosphorus fractionation revealed that inorganic P (Al/Fe-bound P and Ca-bound P) and residual P were the main P pools in soil, whereas water-soluble P accounted for approximately 70% of TP in biosolids. Little organic P was found in either the soil or biosolids. Concentrations of water-soluble P, bioavailable inorganic P (NaHCO3 Pi) and potentially bioavailable inorganic P (NaOH Pi) in both 0-10 and 10-25 cm depths were significantly higher in the high biosolids treatment than in the control. Mass balance calculation indicated that most P applied with biosolids was retained by the top soil (0-25 cm). The standard biosolids treatment (equivalent to 300 kg N ha(-1) applied every three years) had no significant effect on concentrations of TP, Mehlich 3 P and Olsen P, and P fractions in soil. The results indicate that the soil had the capacity to retain most biosolids-derived P, and there was a minimal risk of P losses via leaching in the medium term in the sandy forest soil because of the repeated biosolids application, particularly at the standard rate. Application to low-fertility forest land can be used as an environmentally friendly option for biosolids management. When biosolids are applied at a rate to meet the N requirement of the tree crop, it can take a very long time before the forest soil is saturated with P. However, when a biosolids product contains high concentrations of P and is applied at a high rate, the forest ecosystem may not have the capacity to retain all P applied with biosolids in the long term.

Soil carbon pool and effects of soil fertility in seeded alfalfa fields on the semi-arid Loess Plateau in China

The dynamics of the soil organic carbon pool and soil fertility were studied in soils with different number of growing years of alfalfa ( Medicago sativa L.) in the semiarid Loess Plateau of China. The soil water content and soil water potential decreased and the depth of desiccated layers grew with the number of growing years of alfalfa. The soil organic C (SOC) cannot be enhanced on short timescales in these unfertilized and mowed-alfalfa grasslands in the topsoil, but the light fraction of organic C (LFOC), soil microbial biomass C (MBC) and microbial biomass N (MBN) all increased with the number of growing years. When alfalfa had been growing for more than 13 yr, the soil MBC increased slowly, suggesting that the MBC value is likely to reach a constant level. SOC, soil total P (STP), available P (AvaiP) and the ratio of SOC to soil total N (C/N) all decreased monotonically with the growing years of alfalfa up to 13 yr and then increased. SOC was significantly positively correlated with STP, AvaiP, soil total C (STC) and soil total N (STN) ( R=0.627**, 0.691**, 0.497*, 0.546*, respectively). MBC and LFOC were significantly positively correlated with the number of growing years of alfalfa ( R=0.873*** and 0.521*, respectively), and LFOC was more sensitive to vegetation components, degree of cover and landform than to the number of years of growth. SOC showed a significant negative correlation with LFOC/SOC and MBC/SOC ( R=−0.689**, −0.693**, respectively). A significant positive correlation exists between MBC and soil inorganic C (SIC). LFOC, MBC, LFOC/SOC and MBC/SOC were all significantly positively correlated with each other. Therefore, practices that involve water-harvesting technologies and add residues and phosphate fertilizer to soils should be promoted to improve soil nutrients and hydration and to postpone the degradation of alfalfa grasslands under long-term alfalfa production.

Increase in phosphorus concentration of a clay loam surface soil receiving repeated annual feedlot cattle manure applications in southern Alberta

Migration of P from soils to water resources poses a risk of surface water eutrophication, and increase in P concentration in soils through manure or fertilizer addition would exace rbate this problem. Investigating the rate of increase in P concentration of surface soil receiving livestock manure is crucial to the development of best manure management strategies and prevention of eutrophication of aquatic systems. In this study, the changes in P concentrations of surface soils (0- to 15-cm depth) receiving 25 annual manure applications at rates of 0, 30, 60 and 90 Mg ha-1 yr-1 under non-irrigated conditions and at rates of 0, 60, 120 and 180 Mg ha-1 yr-1 under irrigated conditions were examined. The soil test P (STP) and total P (TP) of the surface soil increased with the TP through manure application over a 25-yr period. The STP pool was about 38% of the soil TP pool, similar to ratios of STP to TP in feedlot cattle manure. While the high proportion of STP to TP could be beneficial for crop production, it could also increase the potential for P losses from these soils through runoff and leaching. The changes in TP and STP concentrations of the surface soil were modelled with an expone ntial rise to maximum function: TP = 0.69 + 5.06 (1 − e(−0.087x)) and STP = 0.029 + 2.21 (1 − e(−0.082x)) where x is the cumulative TP applied. Although the model was developed for a specific soil and type of manure, it could be adapted to other soils or manure sources by adjusting the model coefficients for the particular soil and/or manure type. These adjustments would not require as extensive a data set as was required to develop the original model. This model could be used to determine the amount of TP that could be applied for a given critical STP. Producers, regulatory agencies, planners, and extension specialists could also use this model to make decisions on manure P management. Key words: Long-term cattle manure application, total phosphorus, available phosphorus, rate of accumulation, non-irrigated and irrigated cropping

Survival of native plants of Hawkesbury Sandstone communities with additional nutrients: effect of plant age and habitat

Australian soils are naturally low in nutrient concentrations, particularly nitrogen (N) and phosphorus (P). Native plants are well adapted to low-nutrient soils, and can be adversely affected when exposed to higher concentrations of nutrients. The Hawkesbury Sandstone soils in northern Sydney are naturally low in nutrients, but often receive additional nutrient input from urban stormwater run-off. Increases in soil nutrients in urban bushland are associated with the presence of exotic species, and the decline in the diversity of native species. This study tested the hypothesis that high concentrations of nutrients, in particular P, in the disturbed soils of urban bushland, reduce survival of native plants. We examined the survival of native species under five different nutrient concentrations that are typical of nutrient-enriched urban bushland soil, in two glasshouse experiments. The experiments examined both survival of seedlings and survival of 6-month-old plants. We used native species that are adapted to both nutrient-poor and nutrient-rich soils. In general, the survival of native plants decreased with increasing nutrient concentrations. At soil total-P concentrations &gt;200 mg kg–1, most plants died. Seedlings were more sensitive to added nutrients than the 6-month-old plants. Species that were from higher-nutrient soil had consistently higher survival than species from low-nutrient soils, under the nutrient addition treatments. These results suggest that at high soil nutrient concentrations typical of stormwater-affected urban bushland, native plant species of low-nutrient soils will be unable to survive. If ecological restoration works are to be done in such areas, replanting with more mature plants from naturally high-nutrient habitats is likely to be the most successful. However, restoration of these areas may have limited success and they are likely to remain dominated by exotic plant species.