首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
  相似文献   

2.
Adoption of input‐responsive varieties enhanced food production during the second half of the 20th century. However, even bigger challenges lie ahead because of the growing societal demands. For example, the global population of 7.2 billion in 2013 is projected to reach 9.2 billion by 2050 and stabilize at 10 billion by 2100. The growing and increasingly affluent population, with preference towards more and more meat‐based diet, is likely to jeopardize the finite, fragile, and dwindling soil and water resources which are already under great stress in densely populated countries in Asia and elsewhere. Economic growth and increase in gross domestic product also lead to generation of waste or by‐products, along with contamination and eutrophication of water resources. International trade in food/feed products also involves transfer of virtual water, which is a serious issue when water‐scarce countries export virtual water to water‐endowed countries. The problem is confounded by the present and future climate change driven by the growing energy demands of the carbon civilization. Thus, adaptation to climate change represents both a threat and an opportunity for sustainable development. Adaptive strategies must be sustainable socially and environmentally and advance the Millennium Development Goals, while buffering agroecosystems against extreme climate events (e.g., pedologic, agronomic, and ecologic drought). Thus, recognizing and addressing the water‐soil‐waste nexus is important to achieving climate‐strategic agriculture. Sustainable intensification of agroecosystems, producing more per unit consumption of essential resources, must consider judicious management of hydrological and biogeochemical cycles (C, N, P, S). The soil C pool must be managed and enhanced to offset anthropogenic emissions, and mitigate/adapt to the climate change. The pace of adoption of recommended land use and soil‐/plant‐/animal‐management practices can be kept at par with advances in scientific knowledge through continuous dialogue between scientists on the one hand and policy makers / land managers on the other to translate research data into policy and action plans.  相似文献   

3.
Under‐ as well as overfertilization with nitrogen (N) will result in economic loss for the farmer due to reduced yields and quality of the products. Also from an ecological perspective, it is important that the grower makes the correct decision on how much and when to apply N for a certain crop to minimize impacts on the environment. To aggravate the situation, N is a substance that is present in many compartments in different forms (nitrate, ammonium, organic N, etc.) in the soil‐plant environment and takes part in various processes (e.g., mineralization, immobilization, leaching, denitrification, etc.). Today, many N‐recommendation systems are mainly based on yield expectation. However, yields are not stable from year to year for a given field. Also the processes that determine the N supply from other sources than fertilizer are not predictable at the start of the growing season. Different methodological approaches are reviewed that have been introduced to improve N‐fertilizer recommendations for arable crops. Many soil‐based methods have been developed to measure soil mineral N (SMN) that is available for plants at a given sampling date. Soil sampling at the start of the growing period and analyzing for the amount of NO ‐N (and NH ‐N) is a widespread approach in Europe and North America. Based on data from field calibrations, the SMN pool is filled up with fertilizer N to a recommended amount. Depending on pre‐crop, use of organic manure, or soil characteristics, the recommendation might be modified (±10–50 kg N ha–1). Another set of soil methods has been established to estimate the amount of N that is mineralized from soil organic matter, plant residues, and/or organic manure. From the huge range of methods proposed so far, simple mild extraction procedures have gained most interest, but introduction into practical recommendation schemes has been rather limited. Plant‐analytical procedures cover the whole range from quantitative laboratory analysis to semiquantitative “quick” tests carried out in the field. The main idea is that the plant itself is the best indicator for the N supply from any source within the growth period. In‐field methods like the nitrate plant sap/petiole test and chlorophyll measurements with hand‐held devices or via remote sensing are regarded as most promising, because with these methods an adequate adjustment of the N‐fertilizer application strategy within the season is feasible. Prerequisite is a fertilization strategy that is based on several N applications and not on a one‐go approach.  相似文献   

4.
The main objective of this study was to analyse how different sewage sludges influence soil wetting and drying dynamics. Three composted and three thermally‐dried municipal sludges from different wastewater plants located in Catalonia (NE Spain) were mixed with a mine‐soil obtained from a limestone quarry. Measurements of the time required to reach zero contact angle () and water holding time (WHT) provided information on the time required for a mine‐soil to reach its complete wettability and the residence time of water stored between ?0.75 and ?25 MPa of soil suction, respectively. One month after sludge amendments, one composted and one thermally‐dried sludge significantly increased . WHT was increased in the mine‐soil treated by composted sludges (50.6% by Blanes' sludge, 65.5% by Manresa's sludge and 52.5% by Vilaseca's sludge) one month after sludge amendments. The amount of water retained in the mine‐soil was increased by all composted sludges and one thermally‐dried sludge after one month (by 42.3% with Blanes' sludge, 42.3% with Manresa's sludge, 65.7% with Vilaseca's sludge and 23.9% with Mataró's sludge) and one year after sludge amendments and at a small suction. Increments in WHT corresponded with the amount of water retained so the time‐scale of soil water availability should also be considered. The value was modified mainly by increments in carbon stock and microbial biomass, while the WHT was modified mainly by increments in pH and electrical conductivity. Under similar air‐drying conditions, mine‐soil treated with composted sludges retained more water for longer compared with thermally‐dried sludges.  相似文献   

5.
In spite of several published studies we have an incomplete understanding of the ion‐release mechanisms and characteristics of polymer‐coated fertilizers (PCF). Here we extend current conceptual models describing release mechanisms and describe the critical effects of substrate moisture and temperature on macro‐ and micronutrient release of three PCF types: Polyon®, Nutricote®, and Osmocote®. Nutrient release was quantified at weekly intervals for up to 300 d from 5°C to 40°C in water and chemically inert sand, substrates that allowed release quantification without confounding effects of ion sorption/desorption. At least two release‐timeframe formulations of each PCF type were studied and all products had similar nutrient concentrations to allow isolation of the effect of coating technology. Contrary to several studies, our data and model indicate that there is no significant difference in nutrient‐release rates in water and a moist, solid substrate. This means that release rates determined in water can be used to model bio‐available nutrient concentrations in moist soil or soilless media where sorption/desorption properties alter concentrations after release. Across all PCF, the nutrients most affected by temperature were typically N, K, B, Cu, and Zn, while the least affected were P, Mg, and Fe. We also found consistent differences among the coating technologies. Osmocote fertilizers released faster than specified at both high and low temperatures. Nutricote had relatively steady release rates over time and a nonlinear response to temperature. Polyon released more slowly than specified but replicate samples were highly uniform.  相似文献   

6.
Currently, potassium (K)‐ and phosphate (P)‐fertilizer recommendation in Germany is based on standardized soil‐testing procedures, the results of which are interpreted in terms of nutrient availability. Although site‐specific soil and plant properties (e.g., clay and carbon content, pH, crop species) influence the relation between soil nutrient content and fertilizer effectiveness, most of these factors are not accounted for quantitatively when assessing fertilizer demand. Recent re‐evaluations of field observations suggest that even for soil nutrient contents well within the range considered to indicate P or K deficiency, fertilizer applications often resulted in no yield increase. In this study, results from P‐ and K‐fertilization trials (in total about 9000 experimental harvests) conducted during the past decades in Germany and Austria were re‐analyzed using a nonparametric data‐mining procedure which consists of a successive segmentation of the data pool in order to elaborate a modified recommendation scheme. In addition to soil nutrient content, fertilizer‐application rates, nutrient‐use efficiency, and site properties such as pH, clay content, and soil organic matter, have a distinct influence on yield increase compared to an unfertilized control. For K, nutrient‐use efficiency had the largest influence, followed by soil‐test K content, whereas for P, the influence of soil‐test P content was largest, followed by pH and clay content. The results may be used in a novel approach to predict the probability of yield increase for a specified combination of crop species, fertilizer‐application rate, and site‐specific data.  相似文献   

7.
Wheat breeders need a nondestructive method to rapidly sort high‐ or low‐protein single kernels from samples for their breeding programs. For this reason, a commercial color sorter equipped with near‐infrared filters was evaluated for its potential to sort high‐ and low‐protein single wheat kernels. Hard red winter and hard white wheat cultivars with protein content >12.5% (classed as high‐protein, 12% moisture basis) or < 11.5% (classed as low‐protein) were blended in proportions of 50:50 and 95:5 (or 5:95) mass. These wheat blends were sorted using five passes that removed 10% of the mass for each pass. The bulk protein content of accepted kernels (accepts) and rejected kernels (rejects) were measured for each pass. For 50:50 blends, the protein in the first‐pass rejects changed as much as 1%. For the accepts, each pass changed the protein content of accepts by ≈0.1%, depending on wheat blends. At most, two re‐sorts of accepts would be required to move 95:5 blends in the direction of the dominant protein content. The 95:5 and 50:50 blends approximate the low‐ and high‐protein mixture range of early generation wheat populations, and thus the sorter has potential to aid breeders in purifying samples for developing high‐ or low‐protein wheat. Results indicate that sorting was partly driven by color and vitreousness differences between high‐ and low‐protein fractions. Development of a new background specific for high‐ or low‐protein and fabrication of better optical filters for protein might help improve the sorter performance.  相似文献   

8.
A hydroponic experiment was conducted to investigate the dynamic variations of cadmium (Cd) uptake and transport, non‐protein thiols (NPT) and glutathione (GSH) concentrations, glutathione S‐transferase (GST) activity and lipid peroxidation under Cd stress in order to clarify the role of NPT and GST in reducing Cd toxicity and translocation in rice (Oryza sativa L.). Cadmium accumulation was initially fast and then slowed down with increasing time of Cd exposure. However, the rice growth inhibition and lipid peroxidation were not intense until 5d after Cd treatment, even though Cd kept accumulating in root and shoot, suggesting that Cd may be effectively detoxified. The concentrations of NPT in root increased gradually until 5d after Cd stress, whereas those in shoot showed no significant changes. The concentration of shoot GSH was progressively enhanced upon Cd treatment, while it gradually declined in root after an initial increase. The GST activity varied similarly in root and shoot, reaching the maximum level on 3rd day, followed by a significant decrease 5 d after Cd application. Significant increases of lipid peroxidation and root‐to‐shoot translocation on 7th day indicate that the equilibrium in Cd‐thiol interaction in rice might be disturbed upon the prolonged Cd exposure. In summary, our results suggest that Cd may be retained and detoxified in rice root through chelation with thiol compounds and subsequent sequestration.  相似文献   

9.
  相似文献   

10.
Rheological methods are applied whenever flow behavior of substances needs to be investigated on a particle‐to‐particle scale executed by a parallel‐plate rheometer. Under oscillation, mechanical effects due to trafficking or vibrations caused by agricultural and forest machinery can be simulated by conducting amplitude‐sweep tests. Hooke's law of elasticity, Newton's law for ideal fluids (viscosity), Mohr‐Coulomb's equation, and, finally, Bingham's yielding are well‐known relationships and parameters in the field of rheology. This paper aims to introduce rheometry as a suitable method to determine the mechanical behavior of salt‐affected soils when subjected to external stresses. Potassium‐treated loamy sand from Halle and loamy silt from Kassel, both sites located in Germany, as well as loess from Israel, saturated with NaCl solutions in several concentrations were analyzed. From the stress‐strain–relationship parameters like the storage modulus G′ and the loss modulus G″, yield stress τy and the linear viscoelastic (LVE)–deformation range including the deformation limit γL, i.e., the transition from an elastic to a viscous state, were determined and calculated, respectively. With respect to salt effects, amplitude‐sweep tests on originally CaCO3‐rich Avdat Loess show an increasing stability if saturated with higher NaCl concentrations. Comparable tests with K+‐rich substrates from Halle and Kassel evinced similar tendencies including the phenomenon of a critical K+ content, which becomes more obvious in case of the drained (–60h Pa) loamy‐silt samples from Kassel. Nevertheless, a higher microstructural stability is given in both substrates from Halle and Kassel, affected by different water contents, in general, which influence the exchange and availability of cations. The results verify that oscillatory tests are applicable for retracing salt‐induced effects, beside those ones, which are influenced by texture, current water content, and/or further chemical parameters.  相似文献   

11.
A total of 1,176 grain samples representing 10 different single‐ and double‐mutant genotypic classes of specialty starch corn were used for developing various classification models based on near‐infrared transmittance spectra. The genotypes used included amylose‐extender (ae), dull (du), sugary‐2 (su2), waxy (wx), ae wx, ae du, ae su2, du wx and du su2. Two‐class classification models (only two genotypes compared) were developed using partial least squares analysis (PLS) while three‐way and multiclass models were examined using principal component analysis (PCA). The effectiveness of the calibrations was evaluated by examining the percentage of unknown grain samples incorrectly classified. In general, two‐class models performed better than multiclass models. However, they did not show improvement when discriminating among genotypes with overlapping amylose contents such ae du vs. ae and ae su2 vs. ae. Three‐way models including double‐mutants and their corresponding single‐mutant counterparts had misclassification percentages typically <5% using 14 PCA factors but again, with the exception of models including genotypes with overlapping amylose contents such as ae du vs. ae vs. du. The best multiclass model using all 10 genotypic classes simultaneously revealed only two classes (ae su2 and du) with misclassification rates >10% based on 16 PCA factors. This study demonstrates that, depending on the material to be considered, near‐infrared transmittance spectroscopy could be useful when segregation of specialty starch hybrids grain from other grain types is necessary.  相似文献   

12.
This study focused on the performance of two hulless barley cultivars (Doyce and Merlin) and one commercial husked (hulled) sample using experimental milling. The purpose was to use experimental milling as a preliminary indicator of the milled streams with potential use for fuel ethanol production and fractions that could be used in food products. Experimental mills designed for flour production evaluation from wheat were Chopin CD1 Auto, Quadrumat Sr, Buhler, and an experimental Ross roller mill walking flow. Results indicate that the shorts had the highest levels of β‐glucan from all the mills. However, the β‐glucan content in the break flours was highest with the roller mill walking flow and the Chopin CD1 for the hulless cultivars. The lowest β‐glucan content in the break flour was found with the Buhler for Doyce. Break flour and, to a slightly lesser extent, reduction flour from all cultivars tested on all mills contained the highest starch content (up to 83%) and are therefore most appropriate for use as feedstock for fuel ethanol production. Conversely, bran and shorts from all cultivars and mills were lowest in starch (as low as 25%), making them ideal as low‐starch food ingredients.  相似文献   

13.
Approximately 40% of New Zealand's land mass is fertilized grassland with entirely non‐native plants, but currently there is substantially increased interest in restoration of native plants into contemporary agricultural matrices. Native vegetation is adapted to more acid and less fertile soils and their establishment and growth may be constrained by nutrient spillover from agricultural land. We investigated plant–soil interactions of native N‐fixing and early successional non N‐fixing plants in soils with variable fertility. The effects of soil amendments of urea (100 and 300 kg N ha?1), lime (6000 kg CaCO3 ha?1), and superphosphate (470 kg ha?1) and combinations of these treatments were evaluated in a glasshouse pot trial. Plant growth, soil pH, soil mineral N, Olsen P and nodule nitrogenase activity in N‐fixing plants were measured. Urea amendments to soil were not inhibitory to the growth of native N‐fixing plants at lower N application rates; two species responded positively to combinations of N, P and lime. Phosphate enrichment enhanced nodulation in N‐fixers, but nitrogen inhibited nodulation, reduced soil pH and provided higher nitrate concentrations in soil. The contribution of mineral N to soil from the 1‐year old N‐fixing plants was small, in amounts extrapolated to be 10–14 kg ha?1 y?1. Urea, applied both alone and in conjunction with other amendments, enhanced the growth of the non N‐fixing species, which exploited mineral N more efficiently; without N, application of lime and P had little effect or was detrimental. The results showed native N‐fixing plants can be embedded in agroecology systems without significant risk of further increasing soil fertility or enhancing nitrate leaching.  相似文献   

14.
Soil structure, moisture content and strength have profound effects on plant growth. Traditional methods for monitoring soil condition are invasive and therefore may affect the samples of interest. We have demonstrated the potential of a non‐invasive measurement technique for the in situ monitoring of soil physical properties in the field. When soils are regarded as porous and elastic media, sub‐surface wave propagation can be indicative of the soil status. Such propagation can be initiated by airborne sound through acoustic‐to‐seismic (A–S) coupling. Measurements of near‐surface sound pressure and acoustically induced soil particle motion can be exploited to estimate the pore‐related and elastic properties of soils. We have conducted laboratory measurements on dry and wet sand and field measurements on an arable soil growing wheat using a compression driver, microphones and a laser Doppler vibrometer. The excitation levels were chosen so as to reduce the influence of soil non‐linearity while still yielding sufficient signal‐to‐noise ratios. Measured data were compared with model predictions based on wave propagation in layered homogeneous isotropic poro‐elastic media described by linear Biot‐Stoll theory. Soil properties were estimated through an optimization process minimizing the differences between the measurements and predictions. Latin hypercube sampling was adopted to ensure uniform seeding for optimization throughout the multi‐dimensional search space. The fitted soil characteristics are air permeability, porosity, P‐/S‐wave speeds (related to bulk and rigidity moduli) and a loss factor. Layer depth was also estimated for multi‐layered samples. The current work has demonstrated that soil can be characterized non‐invasively by using A–S coupling. It is also shown that field soils can be represented adequately by multiple homogeneous layers.  相似文献   

15.
We examined the effects of salicylate, glutamate and glucose on sulphur (S) immobilization and re‐mineralization in three calcareous soils: from arable, fallow and forest managements. Each of the three substrates, at a single rate of carbon (1000 mg C kg−1 soil) was added to the three soils and then incubated with NaSO4 plus Na2SO4 for 1, 2, 6 or 12 weeks prior to analysis. The extraction of the immobilized S was performed with either hot water (HW‐S) or 3 m hydrochloric acid (HCl‐S). Except for the forest soil, the average amounts of immobilized S increased in the order control < salicylate < glutamate < glucose. Across all soils, substrate addition significantly decreased the average value of HCl‐S expressed as a percentage of immobilized S compared with that of the control. The decreases in HCl‐S (58 − 100%) were substrate‐ and time‐independent, suggesting a heterogeneous action of HCl. In contrast, except for the forest soil, we found substantial declines in the average percentage values of HW‐S (21 − 75% of the immobilized S) in the order control > salicylate > glutamate = glucose, suggesting that the hot‐water action was substrate dependent. In addition, the proportion of HW‐S decreased with increasing incubation time, indicating that the youngest immobilized S was the most labile. Thus, hot water extracted more homogeneous S compounds than HCl. Sulphur immobilization induced by glutamate and glucose produced more recalcitrant S products (small quantities of 35S re‐mineralization) than that induced by salicylate. Glutamate tended to generate more recalcitrant S compounds than glucose. Hot‐water extractable S was a valuable and rapid indicator of readily labile organic S. Consequent microbial S immobilization resulting from glucose or glutamate addition was followed by a small rate of re‐mineralization of immobilized S.  相似文献   

16.
Remediation of an uranium‐mine soil from Settendorf (East Germany) includes phytoextraction under conditions which make its heavy metals more plant‐available but less leachable. A second way is active inhibition of heavy metal uptake by the plant. In a pot trial with Chinese cabbage (Brassica chinensis L.), planted and unplanted soil samples were daily irrigated with deionized water or aqueous solutions with a total of (g (kg soil)–1) CaCl2 (0.26 Ca), NH4Cl (1.39), casein, sucrose, citric acid (13), and an extract of rape (B. napus L.) shoots (13 DW) in a phytotron for 26 d. Water‐irrigated plants were also treated with a 50 mM citric acid solution (10.5 g (kg soil)–1) 6 and 7 d prior to harvesting. Total elements in plant tissue and soluble elements in aqueous extracts from control and postharvest soils were determined by ICP‐AES. Supplements of NH , and the NH ‐generating casein and rape extract reduced soil pH during nitrification, and increased plant uptake of Cd, Cu, Ni, and Zn. Citric acid at 50 mM adjusted soil to pH 4.5–6.0 and enhanced uptake of all elements. Long‐term application of sucrose and citric acid increased pH and inhibited uptake of Cd, Cr, Cu, Ni, and Zn. Contemporarily, leaching of heavy metals and humic substances was lowest with Ca and NH and highest with sucrose and citric acid amendments. It is concluded that Chinese cabbage grown for chelate‐assisted phytoextraction should be supplied with Ca and NH to obtain a high plant biomass on soil with a low hazard of leaching. Metal uptake should be stimulated by application of chelator 7 d prior to harvesting. Undesired uptake of heavy metals by Chinese cabbage determined as food should be inhibited with carbohydrate amendments. Long‐term application of NH or chelator, which reduces the solubility of certain elements but increases their uptake moderately, is recommended as a tool for continuous phytoextraction technologies.  相似文献   

17.
Soil structure formation is essential to all soil ecosystem functions and services. This study aims to quantify changes in soil structure and microbial activity during and after field incubation and examine the effect of carbon, organic amendment and clay on aggregate characteristics. Five soils dominated by illites, one kaolinitic soil and one smectitic soil were sieved to 2 mm, and each soil was divided into two parts and one part amended with ground rape shoots (7.5 t ha?1) as an organic amendment. Samples were incubated in the field for 20 months with periodic sampling to measure water‐dispersible clay (WDC) and fluorescein diacetate activity (FDA). After incubation, WDC and FDA were measured on air‐dried 1–2‐mm aggregates. Tensile strength was measured on four aggregate classes (1–2, 1–4, 4–8 and 8–16 mm) and results used to assess soil friability and workability. Intact cores were also sampled to determine compressive strength. During incubation, the amount of WDC depended on soil carbon content while the trends correlated with moisture content. Organic amendment only yielded modest decreases (mean of 14% across all sampling times and soils) in WDC, but it was sufficient to stimulate the microbial community (65–100% increase in FDA). Incubation led to significant macroaggregate formation (>2 mm) for all soils. Friability and strength of newly‐formed aggregates were negatively correlated with clay content and carbon content, respectively. Soil workability was best for the kaolinite‐rich soil and poorest for the smectite‐rich soil; for illitic soils, workability increased with increasing organic carbon content. Organic amendment decreased the compression susceptibility of intact, incubated samples at smaller stress values (<200 kPa).  相似文献   

18.
  相似文献   

19.
Two experiments were conducted to study the effect of grafting on nitrogen‐use efficiency (NUE) in mini‐watermelon plants. In the first study, mini‐watermelon plants (Citrullus lanatus [Thumb.] Matsum. and Nakai cv. Minirossa) either ungrafted or grafted onto Macis, Vita (Lagenaria siceraria [Mol.] Standl.), PS1313, and RP15 (Cucurbita maxima Duchesne × Cucurbita moschata Duchesne) rootstocks grown in hydroponics were compared in terms of shoot dry biomass, leaf area, root‐to‐shoot ratio, SPAD index, shoot N uptake, and nitrate reductase (NR) activity 40 d after transplantation in response to nitrate concentration in the nutrient solution (0.5, 2.5, 5, 10, 15, or 20 mM of NO$ _3^- $ ). In the second experiment, the suitability of a selected rootstock with high NUE (Vita) to improve crop performance and NUE of grafted mini‐watermelon plants was evaluated under field conditions. In the hydroponic experiment mini‐watermelon grafted onto Vita rootstock needed the lowest nitrate concentration (1.31 mM of NO3) in the nutrient solution to reach half maximum shoot dry weight. Total leaf area, SPAD index, and shoot N uptake increased in response to an increase of N concentration in the nutrient solution. At 2.5 mM NO$ _3^- $ , mini‐watermelon grafted on either Vita or RP15 had the highest NR activity whereas no significant difference was observed at 10 mM NO$ _3^- $ . The open‐field study indicated that increasing N‐fertilization rates from 0 to 100 kg ha–1 improved total and marketable yields of mini‐watermelon plants while decreasing NUE. When averaged over N levels, the marketable yield, NUE, N‐uptake efficiency, and N‐utilization efficiency were significantly higher by 39%, 38%, 21%, and 17%, respectively, in Minirossa grafted onto Vita compared to ungrafted Minirossa plants. Therefore, grafting mini‐watermelon plants onto selected rootstocks can be used as a quick and effective method for improving productivity and NUE.  相似文献   

20.
A large variety of extraction methods are used worldwide for the estimation of “plant‐available P” in soils. In Germany, the standard extractants are Calcium‐Acetate‐Lactate (CAL) and Double‐Lactate (DL). Until now there is no validated transformation procedure available and studies on the comparability of both methods have reported conflicting evidence. The uncertainty about the equivalence of CAL‐P and DL‐P hinders a direct comparison of the P fertility status and P fertilizer recommendations across Germany. Based on 136 datasets for soil samples from an interlaboratory comparison program and three P fertilization field trial sites, for which plant‐available P had been determined by both the CAL and DL method, we assessed the comparability of both extraction methods and derived simple and multiple regression equations to transform DL‐P into CAL‐P values. On average, DL extracted 30% more P than CAL. However, this strongly depended on soil pH and carbonate content. A simple linear regression model explained 70% of the variance. However, if simple linear regression models were fitted to pH‐specific samples (pH range 4.5 to 7.0) the R2 increased to 0.96. Based on an independent validation dataset (n = 48) we demonstrated that such pH‐specific models were more accurate than models that did not consider pH when transforming DL‐P to CAL‐P values. Multiple regression results showed that out of soil pH, Corg, Nt, and C : N ratio, only soil pH improved the model. The transformation equations in this study provide a step towards an improved comparability of P fertility status assessments of soils across Germany.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号