Impact Of Agricultural Management Practices Research Articles

Bacterial community shifts occur primarily through rhizosphere expansion in response to subsoil amendments.

To comprehensively evaluate the impact of agricultural management practices on soil productivity, it is imperative to conduct a thorough analysis of soil bacterial ecology. Deep-banding nutrient-rich amendments is a soil management practice that aims to improve plant growth and soil structure by addressing the plant-growth constraints posed by dense-clay subsoils. However, the response of bacterial communities to deep-banded amendments has not been thoroughly studied. To address this knowledge gap, we conducted a controlled-environment column experiment to examine the effects of different types of soil amendments (poultry litter, wheat straw + chemical fertiliser and chemical fertiliser alone) on bacterial taxonomic composition in simulated dense-clay subsoils. We evaluated the bacterial taxonomic and ecological group composition in soils beside and below the amendment using 16S rRNA amplicon sequencing and robust statistical methods. Our results indicate that deep-banded amendments alter bacterial communities through direct and indirect mechanisms. All amendments directly facilitated a shift in bacterial communities in the absence of growing wheat. However, a combination of amendments with growing wheat led to a more pronounced bacterial community shift which was distinct from and eclipsed the direct impact of the amendments and plants alone. This indirect mechanism was evidenced to be mediated primarily by plant growth and hypothesised to result from an enhancement in wheat root distribution, density and rhizodeposition changes. Therefore, we propose that subsoil amendments regardless of type facilitated an expansion in the rhizosphere which engineered a substantial plant-mediated bacterial community response within the simulated dense-clay subsoils. Overall, our findings highlight the importance of considering the complex and synergistic interactions between soil physicochemical properties, plant growth and bacterial communities when assessing agricultural management strategies for improving soil and plant productivity.

Impact of long-term agricultural management practices on soil organic carbon and soil fertility of paddy fields in Northeastern Thailand

Soil organic carbon (SOC) is an essential indicator of soil quality and soil fertility. Agricultural management practices can influence SOC and soil fertility. The objective of the present study was to evaluate the impact of agricultural management practices on SOC and soil fertility of paddy fields in the northeastern region of Thailand over a 10-year period. Initial data on SOC and soil fertility parameters in the top 20 cm under indigenous management (compost amendment) in Maha Sarakham Province were collected in 2007 by the Khon Kaen Rice Research Center. The data on SOC and soil fertility parameters were collected again in 2016 after 10 years from 130 farmers' fields located in close proximity to the sites from where the initial data were collected in 2007. The impacts of the conversion of indigenous agricultural management practice into government-promoted management practices on SOC and soil fertility were evaluated. The practices were continuous compost amendment (CA) during 10 years as the control, the shift from CA to biofertilizer (BF), to green manuring (GM), and to rice straw (RS) incorporation. Measurements made at the end of the 10-year period showed that the adoption of government-promoted agricultural management practices generally increased SOC and soil fertility. The incorporation of RS resulted in the largest change in total nitrogen (156% increase), SOC concentration (152% increase), and SOC density content (149% increase) over the 10-year period. The same management practice (RS) had the greatest SOC sequestration rate (1.43 Mg ha−1 yr−1). Results demonstrate the value of RS incorporation into agricultural soils over time for improving SOC and soil fertility. Soil incorporation of compost (CA) could be another option for its potential to improve soil fertility.

Visual assessment of the impact of agricultural management practices on soil quality

AbstractThe intensification of agricultural practices to increase food and feed outputs is a pressing challenge causing deterioration of soil quality and soil functions. Such a challenge demands provision of empirical evidence to provide context‐sensitive guidance on agricultural management practices (AMPs) that may enhance soil quality. The objectives of this study are to identify the most promising AMPs (and their combinations) applied by farmers with the most positive effects on soil quality and to evaluate the sensitivity of the soil quality indicators to the applied AMPs. The effect of selected AMPs on soil quality was assessed using a visual soil assessment tool in a total of 138 pairs of plots spread across 14 study site areas in Europe and China covering representative pedo‐climatic zones. The inventory and scoring of soil quality were conducted together with landowners. Results show that 104 pairs show a positive effect of AMPs on soil quality. Higher effects of the AMPs were observed in lower fertile soils (i.e., Podzols and Calcisols) as opposed to higher fertile soils (i.e., Luvisols and Fluvisols). For the single use applications, the AMPs with positive effects were crop rotation; manuring, composting, and no‐tillage; followed by organic agriculture and residue maintenance. Cluster analysis showed that the most promising combinations of AMPs with the most positive effects on soil quality are composed of crop rotation, mulching, and min‐till. The agreement between scientific skills and empirical knowledge in the field identified by the farmers confirm our findings and ensures their applicability.

Impact of agricultural management practices on the nutrient supply potential of soil organic matter under long-term farming systems

Soil organic matter (SOM) has the potential to supply substantial quantities of nutrients [i.e nitrogen (N), phosphorus (P) and sulphur (S)] for plant uptake. Yet there is little understanding of the impact of management on the nutrient supply potential in soils (particularly, P and S). To quantify N, P and S availability from SOM, surface soils (0–10cm) were collected from 14 management practices across three long-term (16–46 years) experimental sites under semi-arid (Luvisol), Mediterranean (Luvisol) and sub-tropical (Vertisol) environments in Australia. The practices comprised conventional (CT) and reduced tillage (RT) with mixed farming, no-till with continuous cropping (NT), and perennial pasture (PP) in the semi-arid Luvisol, while in a Mediterranean direct-drilled continuous cropping system, stubble was either retained (SR) or burnt (SB). Practices on the Vertisol comprised a factorial combination of CT, NT, SR, SB with either 0 (0N) or 90kg urea-Nha−1 (90N) in a continuous cropping system. Soils were incubated under controlled soil moisture and temperature, and cumulative organic C mineralised (Cmin), and net available N, P and S were measured over 126days. In the semi-arid Luvisol, CT and/or RT showed significantly higher Cmin and net available N, P and S than NT and PP. In the Mediterranean Luvisol, Cmin and net available P were not influenced by stubble management. In the Vertisol, CT-SR (cf. CT-SB and NT-SR/SB) with or without N fertilisation significantly increased Cmin, and CT-SR and/or -SB with N fertilisation (cf. CT-SR/SB without N fertilisation and NT-SR and/or -SB with or without N fertilisation) significantly increased net available N and P. This study found a continuous release of net available N (11–49kgNha−1 over 126days) across all management practices, whereas, the release of available P and S was evident only during the first 30days (6–74kgPha−1, −4 to 22kgSha−1), after which microbial immobilisation or clay fixation of P and S predominated, particularly in the Vertisol. In conclusion, the results indicate that SOM is a ready source of plant available P and S (in addition to N), and tillage and stubble retention generally enhanced SOM mineralisation and nutrient release, which varied with soil type.

Soil carbon fractions under maize-wheat system: effect of tillage and nutrient management.

Soil organic carbon plays a major role in sustaining agroecosystems and maintaining environmental quality as it acts as a major source and sink of atmospheric carbon. The present study aims to assess the impact of agricultural management practices on soil organic carbon pools in a maize-wheat cropping system of Indo-Gangetic Plains, India. Soil samples from a split plot design with two tillage systems (bed planting and conventional tillage) and six nutrient treatments (T1 = control, T2 = 120 kg urea-N ha(-1), T3 = T2 (25 % N substituted by FYM), T4 = T2 (25 % N substituted by sewage sludge), T5 = T2 + crop residue, T6 = 100 % organic source (50 % FYM + 25 % biofertilizer + 25 % crop residue) were used for determining the organic carbon pools. Results show that there was a significant improvement in Walkley and Black carbon in soil under integrated and organic nutrient management treatments. KMnO4-oxidizable carbon content of soil varied from 0.63 to 1.50 g kg(-1) in soils and was found to be a better indicator for monitoring the impact of agricultural management practices on quality of soil organic carbon than microbial biomass carbon. Tillage and its interaction were found to significantly influence only those soil organic carbon fractions closely associated with aggregate stability viz, labile polysaccharides and glomalin. The highest amount of C4-derived carbon was found to be in plots receiving recommended doses of N as urea (29 %) followed by control plots (25 %). The carbon management index ranged between 82 to 195 and was better in integrated nutrient sources than ones receiving recommended doses of nutrients through mineral fertilizers alone.

Impacts of Agricultural Management Practices on the Risk of Nitrogen and Phosphorus Losses at Catchment Scales by Using GIS and Index Models

The unreasonable agricultural management measure is the main cause of the risk of nitrogen and phosphorus losses. The objective of this paper was to evaluate the impacts of agricultural management practices on the risk of nitrogen and phosphorus losses at catchment scales based on GIS and integrated index models. The results showed that 93.1% of the catchment was no risk and low risk area, while 6.9% for medium and high risk of nitrogen and phosphorus losses. Spatial analysis of risk index indicated that different agricultural management practices lead to number and proportion of grids are different. At very high risk area, about 599 of grid number is only for the actual management practice, accounting for 0.22% of the total, while at very low risk area, 165884.00 and 60.51% for river buffer zone respectively. Control effect of different agricultural management practices for risk of nitrogen and phosphorus losses is better, which very low and low risk areas of based fertilizer applied deeply and buffer zone construction accounted for 98% and 95.6%, and the control effect sorted as follows: base fertilizer applied deeply> construction of river buffer zone> reduced nitrogen application> reduced phosphorus application.

Impacts of Agricultural Management Practices on the Risk of Nitrogen and Phosphorus Losses at Catchment Scales by Using GIS and Index Models

Impacts of Agricultural Management Practices on the Risk of Nitrogen and Phosphorus Losses at Catchment Scales by Using GIS and Index Models

Seasonal and inter-annual variation of leaching of dissolved organic carbon and nitrogen under long-term manure application in an acidic clay soil in subtropical China

Dissolved organic matter (DOM) plays an important role in soil biological activity and transport of pollutants and nutrients in soils, but very little information is available with regard to the long-term impact of agricultural management practices on the dynamics and fate of DOM in acidic soils. The seasonal and inter-annual variation of dissolved organic carbon (DOC) and nitrogen (DON) contents and leaching were investigated in an acidic clay soil (Ferric Acrisol) by a long-term field lysimeter experiment in subtropical China. The experiment was conducted from 2002 to 2010 with 4 fertilization treatments under maize monoculture: no manure (CK), low-rate manure with 150kgNha−1y−1 (LM), high-rate manure with 600kgNha−1y−1 (HM), and high-rate manure with 600kgNha−1y−1 and lime at 3000kg Ca(OH)2ha−13y−1 (HML). Manure application resulted in a seasonal variation of soil DOC and DON, and significant effects were observed by manure DOC, microbial biomass and soil water content. Soil DOC, which was mainly determined by soil organic matter and soil water content, increased yearly until the seventh year when it was stabilized. Manure application on acidic clay soil did not alter DOC leaching, whereas DON leaching clearly increased after three years of high manure application of 600kgNha–1y–1. The average annual DON leaching losses under long-term manure application had a range of 3.8–5.4kgha–1, accounting for 6–11% of total nitrogen leached. The addition of lime, combined with manure application, produced no impact on soil dynamics and leaching of DOC and DON, with the exception of increasing emission of CO2.

Composição química e desoxinivalenol em trigo da região Centro- Sul do Paraná: adubação nitrogenada em cobertura associada com Azospirillum brasilense

The impact of agricultural management practices on the quality of grain was evaluated in wheat ( Triticum aestivum L. BRS Tangara) from the South Central region of Parana State (Ponta Grossa) in the crop years of 2010 and 2011. The field trial was carried out in succession with soybean (2010) and corn (2011). The treatments included inoculation of seeds with Azospirillum brasilense and increasing levels of nitrogen application in top dressing (0, 30, 60, 90 and 120 kg ha-1). The experimental design was in randomized block, factorial 2 x 5 (inoculation x N levels), with four replications. The parameters evaluated were water activity, moisture, protein, and grain contamination by deoxynivalenol (DON). The data were subjected to analysis of variance, comparison of means by Tukey’s test (p<0.05) and regression for nitrogen levels. The inoculation of seeds with A. brasilense increased the protein content in grain in 2010 (+1.6%; 16.9 g 100g-1) and 2011 (+1.7%, 15.7 g 100g-1), independently of the nitrogen level (p<0.01). Levels of nitrogen in 2010 presented a positive linear response with protein content, increasing by 14.2% using non-inoculated seeds (p<0.01, R2=0.955) and 14.4% for those inoculated with A. brasilense (p<0.01, R2=0.906). However, in 2011 a quadratic response was observed between nitrogen levels and protein content (p<0.01, R2=0.99), with stabilization or reduction in protein content using high levels of nitrogen (?120 kg ha-1). The contamination by DON was greater using high levels of nitrogen (3574 ?g kg-1, 120 kg ha-1; non-inoculated seeds) in 2011, with a quadratic response between nitrogen levels and contamination of grains (p<0.05, R2=0.772). Furthermore, 37.5% of the samples presented contamination by DON higher than the maximum tolerated limit established by Brazilian legislation (2000 ?g kg-1; whole-wheat grain). The data demonstrates that proper management of nitrogen enhances intrinsic effects arising from plant breeding.

Impact of agricultural management practices on soil organic carbon: simulation of Australian wheat systems

Quantifying soil organic carbon (SOC) dynamics at a high spatial and temporal resolution in response to different agricultural management practices and environmental conditions can help identify practices that both sequester carbon in the soil and sustain agricultural productivity. Using an agricultural systems model (the Agricultural Production Systems sIMulator), we conducted a high spatial resolution and long-term (122 years) simulation study to identify the key management practices and environmental variables influencing SOC dynamics in a continuous wheat cropping system in Australia's 96 million ha cereal-growing regions. Agricultural practices included five nitrogen application rates (0-200 kg N ha(-1) in 50 kg N ha(-1) increments), five residue removal rates (0-100% in 25% increments), and five residue incorporation rates (0-100% in 25% increments). We found that the change in SOC during the 122-year simulation was influenced by the management practices of residue removal (linearly negative) and fertilization (nonlinearly positive) - and the environmental variables of initial SOC content (linearly negative) and temperature (nonlinearly negative). The effects of fertilization were strongest at rates up to 50 kg N ha(-1) , and the effects of temperature were strongest where mean annual temperatures exceeded 19 °C. Reducing residue removal and increasing fertilization increased SOC in most areas except Queensland where high rates of SOC decomposition caused by high temperature and soil moisture negated these benefits. Management practices were particularly effective in increasing SOC in south-west Western Australia - an area with low initial SOC. The results can help target agricultural management practices for increasing SOC in the context of local environmental conditions, enabling farmers to contribute to climate change mitigation and sustaining agricultural production.

Carbon losses and primary productivity decline in savannah soils under cotton-cereal rotations in semiarid Togo

Soil degradation in the savannah-derived agroecosystems of West Africa is often associated with rapid depletion of organic carbon stocks in soils of coarse texture. Field experiments were conducted over a period of more than 30 years at two sites in semiarid Togo to test the impact of agricultural management practices on soil C stocks and crop productivity. The resulting datasets were analysed using dynamic simulation models of varying complexity, to study the impact of crop rotation, fertiliser use and crop residue management on soil C dynamics. The models were then used to calculate the size of the annual C inputs necessary to restore C stocks to thresholds that would allow positive crop responses to fertilisers under continuous cultivation. Yields of all crops declined over the 30 years irrespective of crop rotation, fertiliser use or crop residue management. Both seed-cotton and cereal grain yields with fertiliser fluctuated around 1 t ha−1 after 20 years. Rotations that included early maturing sorghum varieties provided larger C inputs to the soil through residue biomass; around 2.5 t C ha−1 year−1. Soil C stocks, originally of 15 t ha−1 after woodland clearance, decreased by around 3 t ha−1 at both sites and for virtually all treatments, reaching lower equilibrium levels after 5–10 years of cultivation. Soil C dynamics were well described with a two-pool SOM model running on an annual time step, with parameter values of 0.25 for the fraction of resistant plant material (K1), 0.15–0.20 for the decomposition rate of labile soil C (K2) and 8–10 t C ha−1 for the fraction of stable C in the soil. Simulated addition of organic matter to the soil 30 years after woodland clearance indicated that additions of 3 t C ha−1 year−1 for 15–20 years would be necessary to build ‘threshold’ soil C stocks of around 13 t ha−1, compatible with positive crop response to fertiliser. The simulated soil C increases of 0.5 to 1.6% per year are comparable with results from long-term experiments in the region. However, the amounts of organic matter necessary to build these soil C stocks are not readily available to resource-poor farmers. These experimental results question the assumption that crop residue removal and lack of fertiliser input are responsible for soil C decline in these soils. Even when residues were incorporated and fertilisers used at high rates, crop C inputs were insufficient to compensate for C losses from these sandy soils under continuous cultivation.

Monitoring changes in soil organic carbon pools, nitrogen, phosphorus, and sulfur under different agricultural management practices in the tropics

Soil organic matter not only affects sustainability of agricultural ecosystems, but also extremely important in maintaining overall quality of environment as soil contains a significant part of global carbon stock. Hence, we attempted to assess the influence of different tillage and nutrient management practices on various stabilized and active soil organic carbon pools, and their contribution to the extractable nitrogen phosphorus and sulfur. Our study confined to the assessment of impact of agricultural management practices on the soil organic carbon pools and extractable nutrients under three important cropping systems, viz. soybean-wheat, maize-wheat, and rice-wheat. Results indicated that there was marginal improvement in Walkley and Black content in soil under integrated and organic nutrient management treatments in soybean-wheat, maize-wheat, and rice-wheat after completion of four cropping cycles. Improvement in stabilized pools of soil organic carbon (SOC) was not proportional to the applied amount of organic manures. While, labile pools of SOC were increased with the increase in amount of added manures. Apparently, green manure (Sesbania) was more effective in enhancing the lability of SOC as compared to farmyard manure and crop residues. The KMnO(4)-oxidizable SOC proved to be more sensitive and consistent as an index of labile pool of SOC compared to microbial biomass carbon. Under different cropping sequences, labile fractions of soil organic carbon exerted consistent positive effect on the extractable nitrogen, phosphorus, and sulfur in soil.

Evaluation of the RZWQM for Simulating Tile Drainage and Leached Nitrate in the Georgia Piedmont

Models have become an important tool for evaluating the impact of agricultural management practices on water quality. We evaluated the Root Zone Water Quality Model (RZWQM version 1.3.2004.213), for simulating tile drainage and NO3 leaching under conventional and no‐tillage management practices in cotton (Gossipium hirsutum L.) production and rye (Secale cereale L.) cover cropping practices in a Cecil (kaolinitic, thermic, Typic Kanhapludult) soil in Georgia, USA. We calibrated the model for tile drainage and NO3 leaching in maize (Zea mays L.) production and for cotton development and water use in a previous study based on experimental data collected from 1992 through 1993 at Watkinsville, GA. For the current study, we used an independent data set collected from 1997 through 2000. Differences in measured and simulated tile drainage were 926 mm in conventional tillage and 712 mm in no‐tillage treatments. Measured and simulated values of leached NO3 were different by 62 and 73 kg ha−1, respectively, for the two tillage treatments. Some of the differences in simulated drainage compared with the calibration study could be attributed to differences in simulated evapotranspiration and runoff. Comparing the simulated and calculated water balances and winter rye production of the calibration study with the current study, however, the effects of winter cover cropping practices during the 4‐yr period at the study site since the model was calibrated have affected the amount of soil water available for drainage and NO3 leaching at the depth of the drains.

The impact of agricultural management practices on nutrient losses to water: data on the effects of soil drainage characteristics

Against the background of increasing nutrient concentrations in Irish water bodies, this study set out to gain information on the potential of agricultural grassland to lose nutrients to water. Overland flow, flow from artificial subsurface drains and stream flow were gauged and sampled during heavy rainfall events. Dissolved reactive phosphorus (DRP), potassium (K), total ammonia (TA), and total oxidised nitrogen (TON) were measured in water samples. When the nutrient concentrations in water were examined in relation to the grassland management practices of the study catchments it emerged that soil P levels, the application of organic and inorganic fertilisers before heavy rainfall and the presence of grazing animals could all influence nutrient concentrations in surface and subsurface drainage water. Overall, the drainage characteristics of soil were found to have a considerable influence on the potential of land to lose nutrients to water.

Impact of row spacing, nitrogen rate, and time on carbon partitioning of switchgrass

Cultivation of switchgrass ( Panicum virgatum L.) as an energy crop could lower atmospheric carbon dioxide (CO 2) levels by replacing fossil fuel and sequestering carbon (C). Information on the details of C partitioning within the switchgrass–soil system is important in order to quantify how much C is sequestered in switchgrass shoots, roots, and soil. No studies of C partitioning in a switchgrass–soil system under field conditions have been conducted. This study was aimed at determining the impact of agricultural management practices, such as row spacing and nitrogen (N) application rate, on C partitioning within the switchgrass–soil system; changes in C partitioning with time after switchgrass establishment were also considered. The results indicate that C storage in switchgrass shoots was higher with wide than narrow rows, and increased with N application rates. These responses were due to higher yields with wide than narrow rows and higher yields as N application rate increased. Carbon storage in shoots was 14.4% higher with 80-cm than 20-cm row spacing. Annual application of 224 kg N ha −1 increased C storage in shoots by 207% and 27% when compared with annual applications of 0 and 112 kg N ha −1 , respectively. Carbon storage increased by 62% over time from 1995 to 1996 in newly established switchgrass on sandy loam soil in the coastal plain of Alabama. Rate of C increase in roots (72%) was higher than in shoots (49%) between 1995 and 1996. Carbon storage was in order of soil C > root C > shoot C in both 1995 and 1996. The root/shoot ratio of C storage was 2.2. It appears that C partitioning to roots plays an important role in C sequestration by switchgrass.

Impacts of agricultural management practices on C sequestration in forest-derived soils of the eastern Corn Belt

Soil organic matter has recently been implicated as an important sink for atmospheric carbon dioxide (CO 2). However, the relative impacts of various agricultural management practices on soil organic matter dynamics and, therefore, C sequestration at spatial scales larger than a single plot or times longer than the typical three year experiment have rarely been reported. Results of maintaining agricultural management practices in the forest-derived soils of the eastern Corn ( Zea mays L.) Belt states of Kentucky, Michigan, Ohio and Pennsylvania (USA) were studied. We found annual organic C input and tillage intensity were the most important factors in affecting C sequestration. The impact of rotation on C sequestration was primarily related to the way it altered annual total C inputs. The removal of above-ground plant biomass and use of cover crops were of lesser importance. The most rapid changes in soil organic matter content occurred during the first five years after a management practice was imposed with slower changes occurring thereafter. Certain management practices, e.g. no-tillage (NT), increased the soil's ability to sequester atmospheric CO 2. The impact of this sequestration will be significant only when these practices are used extensively on a large percentage of cropland and when the C-building practices are maintained. Any soil C sequestered will be rapidly mineralized to CO 2 if the soil organic matter building practices are not maintained.

Simulation of the Impact of Agricultural Management Practices on Chemical Transport in Macroporous Soils

A simulation model capable of describing preferential movement of water and pesticides in macroporous soils has been developed. The model assumes a bi-continuum, with flow and transport in and between each of two coexisting pore domains (matrix and macropore). In each pore domain, water flow is assumed to obey Richards equation and chemical movement is assumed to obey the convection-dispersion equation. Interdomain transfer of water and chemicals occurs under pressure and concentration gradients. The model incorporates features such as root water extraction, rate-limited sorption and desorption, and first-order decay. The macropore volume fractions are allowed to vary with space to accommodate variabilities in soil properties. The model can represent two-dimensions, to simulate the impact of agricultural management practices, such as tillage, irrigation, cropping practice, and organic addition, on flow and transport.

Impacts of Agricultural Management Practices on Soybean and Corn Crops Evident in Ground-truth Data and Thematic Mapper Vegetation Indices

Vegetation indices from Landsat-5 Thematic Mapper (TM) observations on single dates in August 1988, a drought year, and August 1989, a year with wet early season conditions, were used to study the impact of agricultural management and cultural practices on soybean (Glycine max) and corn (Zea mays) crop growth and yield. Management and cultural practices studied included date of planting, tillage, soil association, drainage, plant density, and stress factors. Crop ground-truth information consisted of leaf area index, wet biomass, dry biomass, and grain yield. During both years ground-truth data were collected from at least 50 commercial farms every one to three weeks. Multispectral TM vegetation indices were developed using the mid-infrared bands 5 and 7 as well as the commonly used near-infrared and red bands. Two mid-infrared vegetation indices proved to be particularly useful in identifying management practice impacts on both crops. For both crops, yield and crop growth measurements gave similar trends versus TM vegetation indices. Planting date, plant density, an index of crop stress, and tillage significantly impacted on soybean and corn crop attributes.

Prediction of Soluble Phosphorus Transport in Agricultural Runoff

AbstractThe soluble phosphorus (SP) concentrations of runoff for individual events from agricultural land were predicted using relationships describing soil P desorption kinetics and effective depth of surface soil‐runoff interaction (E). These values were compared with concentrations measured for runoff from 9 grassed and 11 cropped watersheds in the Southern Plains, USA, over a 10‐yr period. Using a constant value of E for a given watershed, measured SP concentrations were over‐estimated by up to 4415% for runoff events of &gt; 0.75 mm in volume. Using a value of E calculated for each runoff event from soil loss, correlation coefficients between measured and predicted values and prediction errors were improved (R2 = 0.95–0.99 and error = 11–18%) compared to use of a constant E value (R2 = 0.21–0.83 error = 38–380%) averaged for each watershed location. Although these improvements did not significantly (5% level) affect estimates of the amounts of SP transported, the improvements will be important from environmental aspects, in terms of assessing the impact of agricultural management practices on P‐related eutrophication for all runoff events.