Changes In Soil Test Research Articles

Updates to the Annual P Loss Estimator (APLE) model.

The Annual P Loss Estimator (APLE) is a spreadsheet-based model developed for predicting annual field-scale P loss in surface runoff and changes in soil test P. This empirically based model was designed for use by those without significant modeling experience. However, a significant limitation with the model is that it does not calculate runoff. Moreover, APLE is deterministic and thus predicts a single value for a given set of inputs, thereby ignoring any uncertainties associated with model inputs. Here, we describe modifications to APLE that allow users to estimate runoff using the Curve Number method. Using Monte Carlo simulations, the updated version of APLE also provides users the ability to account for model input uncertainties in estimating model prediction errors. We provide examples of using the revised version of APLE (ver. 3.0) for calculating P loss from two fields in Mississippi over a 4-yr period and calculating the change in Mehlich-3 P concentrations over a 9-yr period at three locations in Maryland following cessation of P application. Both examples demonstrate that incorporating estimates of uncertainties in both measured data and model predictions provides modelers with a more realistic understanding of the model's performance.

Soil test potassium changes over time following fall potassium application in three western Kentucky soils

AbstractField experiments were conducted under bare‐ground conditions to investigate changes in soil test K levels over 2 yr following fall K applications to Crider, Zanesville, and Grenada soils in western Kentucky. Additional laboratory studies investigated particle size and clay mineralogy of these soils. In field experiments, highest soil test K in the Crider and Zanesville soils occurred 12–15 mo after fall K application. However, seasonal fluctuations in soil test K occurred in all three soils, likely due to fluctuations in precipitation prior to sampling. The Crider and Zanesville soils showed a much more substantial drop in soil test K at 9 and 21 mo after December K application than did the Grenada soil. The 9‐ and 21‐mo samplings were both preceded by 1–2 mo of dry conditions where precipitation was well below the 30‐yr average at the Crider and Zanesville sites. Particle size analysis showed that the Crider and Zanesville soils had a higher clay content than the Grenada soil. Soils with higher amounts of clay particles such as vermiculite have greater potential to trap K during dry periods, making soil test K levels lower than they might be under better soil moisture conditions. Over the course of these experiments, the Crider soil appeared to be more responsive to fall K application than the other soils, showing the greatest increase in soil test K by the following spring. This research illustrates the seasonal fluctuations in soil test K levels that occur naturally in these soils and how precipitation and clay content may influence these fluctuations.

Soil Test Phosphorus and Phosphorus Availability of Swine Manures with Long‐Term Application

Core Ideas Net P additions of 9.8 to 16.1 kg ha−1 were needed to increase soil test P by 1 mg kg−1. Manure P source availability coefficients were 0.99 for liquid manure, 1.08 for solid manure, and 0.97 for composted manure. The long‐term P availability was identical, regardless of the form of swine manure. The long‐term availability of P from swine manure was similar to that of chemical fertilizer. Understanding the form‐specific long‐term effects of manure (liquid, solid, and composted) application on soil P is essential for nutrient management planning. This 8‐yr study aimed to quantify changes in soil test P (STP, Olsen‐P) with application of three forms of swine manure compared with inorganic fertilizer and to calculate the manure P source availability coefficient (PSAC) as the ratio of the specific manure form to inorganic P in providing crop P availability. The STP content increased linearly with both total and net P addition at the surface (0–15 cm) and subsurface (15–30 cm) soil depths, regardless of P source. The slope of STP vs. total or net P addition in the surface layer was steeper for liquid than for solid manure, whereas in the subsurface layer, composted manure showed a greater slope than either liquid or solid manure. The amount of applied P required to increase STP by one unit in the surface layer was 19.9, 15.7, 31.6, and 20.9 kg P ha−1 for inorganic fertilizer and liquid, solid, and composted manure, respectively. When increases in subsoil STP and grain P removal were considered, the net P additions of inorganic fertilizer and liquid, solid, and composted manure needed to increase STP by one unit were 12.2, 9.8, 16.1 and 10.7 kg ha−1, respectively. The PSAC values were 0.99, 1.08, and 0.97 for liquid, solid, and composted manure, respectively. The long‐term availability of swine manure P was largely identical among forms and was similar to that of inorganic fertilizer.

Changes in Olsen P in Relation to P Balance in Contrasting Agricultural Soils

Maintaining soil phosphorus (P) at adequate levels for plant growth requires assessing how the long-term P balance (viz., the difference between P inputs and outputs) results in changes in soil test P. The hypothesis that routinely measured soil properties can help predict the conversion factor of P balance into Olsen P was tested at 39 sites in agricultural areas of the Mediterranean region in Spain. A set of soil samples from each site was analyzed for Olsen P, inorganic P (P extracted using 0.5 mol L−1 H2SO4), pseudototal P (P extracted using 0.5 mol L−1 H2SO4 following ignition at 550 °C), and organic P (the difference between pseudototal P and inorganic P). Organic and Olsen P were uncorrelated in most of the 39 soil sets, which suggests that organic P content changed little with P inputs and outputs. The slopes of the regression lines of Olsen P against pseudototal and inorganic P, which were used as two different measures of the conversion factor, ranged widely (from 0.03 to 0.25 approximately), with their average values (about 0.10) being similar to those found in long-term experiments conducted in temperate areas. Neither conversion factor was significantly correlated with any routinely measured soil property; however, the conversion factor for inorganic P was significantly lower for calcareous soils than for noncalcareous soils. Our negative results suggest the need to isolate the influence of soil properties from that of management systems and environmental factors relating to P dynamics in future studies.

Consequences of Ontario P index recommendations for reduced manure and fertilizer phosphorus applications on corn yields and soil phosphorus

Environmental indices for soil P limit P applications when soil tests and risk of P losses exceed a given threshold. Producers’ reluctance to reduce P inputs often stem from concerns regarding reduced crop production and soil fertility. Our objectives were to identify changes in soil P fractions after 4 yr of repeated manure or fertilizer P applications at rates ≤ crop removal by corn (Zea mays L.), and the impact of these applications on yields. Olsen P and soil P fractions extracted using a modified Hedley P fractionation procedure were measured. Corn yields were nonresponsive to P applications. After 4 yr, Olsen P was 16.6 and 24.6 mg kg−1 at the application rates of 0 and 33 kg P ha−1 yr−1, respectively, for the inorganic fertilizer treatment indicating that soil P drawdown was occurring. Only the most labile forms of Pi (resin and bicarbonate extractable) were affected by treatment, with greater values at higher P application rates. Adherence to Ontario’s P index recommendations for P applications at or below crop removal should not be a crop production concern. Furthermore, given the rate of soil labile P drawdown, routine soil testing (every 3–5 yr) would identify agronomically significant changes in soil test P before the crop yield is impacted.

Soil test phosphorus changes and phosphorus runoff losses in incubated soils treated with livestock manures and synthetic fertilizer

Kumaragamage, D., Flaten, D., Akinremi, O. O., Sawka, C. and Zvomuya, F. 2011. Soil test phosphorus changes and phosphorus runoff losses in incubated soils treated with livestock manures and synthetic fertilizer. Can. J. Soil Sci. 91: 375–384. Source of phosphorus (P) and soil properties influence changes in soil test P (STP) concentrations and P runoff losses in manured and fertilized soils. We compared STP changes and P runoff losses in two soils, a clay loam and a sand, that were either unamended (control), or amended with liquid swine manure (LSM), solid cattle manure (SCM), or monoammonium phosphate (MAP) and incubated for 6 wk. Soil subsamples after incubation were analyzed for STP using Olsen (OP), Modified Kelowna (KP), Mehlich 3 (M3P) and water extraction (WEP) methods. We collected runoff from incubated soils for 60 min under a rainfall simulator, and analyzed for dissolved reactive P (DRP). Magnitude of STP increase in amended soils was greater in sand (19–48%) than in clay loam (7–37%). Increases in STP and DRP runoff concentrations in amended soils generally followed the order; MAP>LSM>SCM. Olsen P, KP and M3P were more accurate than WEP for predicting runoff DRP concentrations and loads, accounting for 43–49% of the variation in P concentrations for the first 30 min of runoff. Olsen P, the currently used STP method for environmental P regulation in Manitoba is sufficiently robust to predict runoff P losses from manure and fertilizer amended soils.

Phosphorus Source Effects on Corn Utilization and Changes in Soil Test

Estimating crop availability of manure P and changes in soil test P (STP) with manure application are essential components of nutrient management planning. The objectives of this field study were to (i) evaluate manure P availability to crop growth through crop P uptake and yield; (ii) determine if second‐year residual P availability from manure application is different than fertilizer; and (iii) evaluate the effect of P source on changes in STP levels. Research plots were established at Arlington and Marshfield, WI, in 2005 on fields with low STP. All P sources (dairy slurry, dairy solid, swine slurry, pelletized poultry litter, and fertilizer) were applied at three target rates of 39, 79, 118 kg total P ha−1 in spring 2005 before planting corn (Zea mays L.). No additional P was applied in 2006. Phosphorus application increased early season biomass, silage and grain yield, and P uptake. In 2005, all manures had silage and grain yields and P uptakes, along with silage P recoveries, that were not significantly different than fertilizer. In 2006, the residual effect of 2005 P applications rates were observed; however, there was no significant difference in any measure of crop response between any manure and fertilizer. These data suggest that manure total P is as available to corn as fertilizer P in the year of application and in the following year. Manure application changed STP levels as much as fertilizer in terms of total P applied.

Soil Test Nutrient Changes Induced by Poultry Litter under Conventional Tillage and No‐Tillage

Poultry litter (PL) can supply N, P, K, and other plant nutrients; however, excessive application may cause environmental problems, depending on management and crop nutrient demand. Changes in soil test (ST) nutrient content in a Cecil soil (a fine, kaolinitic, thermic Typic Kanhapludult) during a 10‐yr period of PL use was evaluated at the USDA‐ARS J. Phil Campbell, Sr., Natural Resource Conservation Center, Watkinsville, GA. During the cotton (Gossypium hirsutum L.) cropping phase (1995–2000), 4.4 Mg PL ha−1 yr−1 resulted in small changes in ST nutrient content in the surface 15 cm. Differences were observed between tillage treatments, with less accumulation of Ca, Mg, and Mn and greater accumulation of Zn for no‐till (NT) than conventional tillage (CT). During the corn (Zea mays L.) cropping phase (2001–2005), average annual PL inputs (11.2 Mg ha−1) increased P and Zn contents, with changes being similar for CT and NT. After 10 yr, ST nutrient contents in the surface 15 cm reflected 25, 4, 45, 26, 17, and 97% of the input from PL for P, K, Ca, Mg, Mn, and Zn, respectively. Changes in soil profile nutrient content (to a depth of 60 cm) from 1997 to 2005 were predominantly at 0 to 15 cm, where P and Zn increased >200%. Accumulation of Ca, K, P, and Zn at lower depths was also observed. Strategies for increasing nutrient removal following repeated long‐term application of PL should be considered to avoid excessive levels of nutrients.

Phosphorus status of diverse soils in Finland as influenced by long-term P fertilisation 2.Changes of soil test values in relation to P balance with references to incorporation depth of residual and freshly applied P

Fertilising with phosphorus (P) ensures continuous supply of an essential growth factor as necessary for productive and sustainable agriculture. The amounts of P required to attain and maintain an adequate P status in the soil were investigated in field experiments at 22 sites in Finland on soils containing large amounts of residual fertiliser P. The effects of five rates (0, 15, 30, 45 and 60 kg ha-1) of annual P application were measured in the soil by chemical methods after 9 to 15 experimental years, and the changes in soil test P values (STP) were compared with P balances. Stratification of P in ley soil by broadcast application of fertilisers was assessed at four sites. The mean changes of STP in the whole topsoil caused by P fertilisation expressed as per cent of the balance difference were 3.5% (0.0159 mg dm-3)/(kg ha-1) in the acid ammonium acetate test (PAc), 4.7% (0.0214 mg dm-3)/(kg ha-1) in water extraction (Pw) and 9.7% (0.058 mg kg-1)/(kg ha-1) in sodium bicarbonate extraction (modified Olsen P). Initially high PAc values tended to slowly decrease at zero P balance, while low values did not change without some particular reason, such as soil acidification or mixing of the topsoil with some of the less fertile subsurface soil. A thin layer of the uppermost soil was quickly enriched by broadcast application of P fertiliser.;

The Influence of Manure Phytic Acid on Phosphorus Solubility in Calcareous Soils

Manure characteristics can influence the potential for P transfer in runoff following land application of manures. This research assessed the influence of manure characteristics on P solubility in calcareous soils using manures from poultry (Gallus Domisticus) fed a variety of grain‐based diets with the manures containing a range of total P (5.6–16.4 g P kg−1), water‐extractable P (WEP, 0.9–4.7 g P kg−1), phytic acid P (0.1–7.6), total N/P ratios (2.6–5.1), and total C/P ratios (19.5–75.7). In addition, mono‐ammonium phosphate fertilizer and reagent grade inositol hexaphosphate (phytic acid [PA]), were included, as well as a control treatment with no P additions. Treatments were incorporated into two soils (Portneuf [Coarse‐silty, mixed, superactive, mesic Durinodic Xeric Haplocalcids] and Millville [Coarse‐silty, carbonatic, mesic Typic Haploxerolls]) at three rates (10, 20, and 40 mg P kg−1) and incubated for a total of 18 wk with subsamples taken at 2, 5, 9, and 18 wk. Soil samples were analyzed for inorganic and organic NaHCO3 (Olsen) extractable P and select soils were analyzed at 0 and 12 wk by 31P nuclear magnetic resonance spectroscopy (NMR) for soil P characterization. The percentage of WEP and PA (of total P) in the manures were linearly related (r2 = 0.94). Increases in Olsen P over time were positively related to the percentage of monoester P in the treatments. At 2 wk, there was a strong negative correlation between the amount of PA added in the treatments and increases in Olsen P. However, by 18 wk, Olsen P was more closely related to the amount of C or N added with the treatments. Changes in PA content of manures due to dietary modification may influence P sorption on calcareous soils in the short‐term while other characteristics such as C/P ratio may exert a stronger influence over changes in soil test P over longer time periods.

Soil Test Phosphorus and Phosphorus Fractions with Long‐Term Phosphorus Addition and Depletion

The fate of fertilizer P in soil during crop production has to be determined to evaluate the long‐term economic value and sustainability of fertilizer practices. We assessed changes in soil test P and soil P fractions with continuous P fertilization and soil P depletion under continuous corn (Zea maysL.) in a Ste. Rosalie clay soil (humic Gleysol; fine, mixed, frigid, Typic Humaquept). Soil samples were analyzed for Mehlich‐3 P (M‐3 P) and P fractions using a modified Hedley's procedure. Soil M‐3 P values remained constant in spite of crop removal in soil not receiving fertilizer for 10 yr. Continuous P fertilization at rates from 44 to 132 P ha−1yr−1increased linearly soil M‐3 P, with 6.3 kg P ha−1of net P addition required to increase M‐3 P by 1 mg P kg−1Residual fertilizer P in soil resulted from the continuous P addition were found predominately in labile inorganic P (LPi) (NaHCO3–Pi) and moderately labile Pi(MLPi) (NaOH‐Pi). Increased P rates favored soil P transformation from LPito MLPi, indicating enhanced soil P retention. With P depletion, soil M‐3 P declined in plots previously receiving 132 kg P ha−1yr−1, with 4.2 kg P ha−1crop P removal decreasing soil M‐3 P by 1 mg P kg−1Continuous crop removal of soil residual P (Res‐P) resulted in decreases in soil LPiand increases in MLPi, an indication of increased retention of Res‐P with time. However, moderately stable Pi(HCl‐Pi) remained constant, both with continuous P addition and P depletion. Conversion of residual fertilizer P to less available P forms in soil was a slow process and thus the fate of the Res‐P should be taken into consideration when developing soil nutrient management plans.

Impact of Banded Potassium on Crop Yield and Soil Potassium in Ridge‐Till Planting

Adequate application of fertilizer K has been identified as a key management practice needed to achieve optimum production in a ridge‐till planting system. However, the impact of K fertilization frequency has not been documented. Additionally, banded application of K also raises questions about the correct procedure to be followed for collection of soil samples. This study was conducted in the fields of three farmers who used the ridge‐till planting system for corn (Zea mays L.) and soybean (Glycine max L.) grown in rotation. Potassium was applied in a subsurface band in the center of existing ridges in the fall of Year 1 before corn and Year 2 before soybean at rates of 0, 18.5, 37.0, 55.5, and 74.0 kg ha−1 To measure the effect of residual K on soybean yield, the rates were doubled and applied only once (before Year 1). Grain yield of both corn and soybean at all sites was not affected by K application. Potassium uptake by young corn plants was increased by K rate, but uptake was not related to yield. Potassium use had no significant effect on K concentration in the most recently matured soybean trifoliate leaves sampled at early bloom. At two sites, banded K produced changes in soil test K to a depth of 15.0 cm at a distance to 15.0 cm from the row.

Nutrient and pH stratification with conventional and no‐till management

This study investigated changes in soil test results associated with sampling depths in fields managed with conventional tillage, no‐till for less than 3 years, no‐till for 3 to 6 years, and no‐till for more than 6 years. Soil samples from depths of 0–5, 0–10, 0–20, and 10–20 cm were collected from 59 fields with different tillage histories from several geologic regions, and analyzed by the North Carolina Department of Agriculture soil test laboratory. Some nutrient stratification was noted in all tillage categories. Soil test phosphorus (P), potassium (K), and zinc (Zn) concentrations were significantly higher in the 0–10 cm depth than in the 10–20 cm depth. Stratification probably results from the prevalence of tillage with disks, chisel plows or subsoilers, which do not mix the soil thoroughly. With the adoption of no‐till methods, stratification becomes even more pronounced. Our data suggest that stratification in pH, calcium (Ca), manganese (Mn), and sulfur (S) is more likely for fields in the early stages of no‐till (less than 6 years) than in longer‐term no‐till. In fields managed with no‐till for less than 3 years or for 3 to 6 years, pH and Ca, Mn, and copper (Cu) concentrations were higher and the S concentration was lower in the surface 0–10 cm layer than in the underlying 10–20 cm soil layer. These differences were not significant for fields managed with no‐till for more than 6 years or with conventional tillage. In fields with low P or K levels, higher nutrient concentrations near the surface result in lower fertilizer rate recommendations with shallower sampling depths. The overall pH effect across geologic regions was very small, generally 0.1 to 0.2 pH unit, so lime recommendation did not vary significantly with sampling depth in most cases. For monitoring changes in plant nutrient and heavy metal concentrations over time, sampling no‐till fields requires even more attention to depth than for conventionally tilled fields.

Yield of corn as affected by potassium on a coastal plain soil

Abstract Corn (Zea mays L.) yields were determined over a four year period on Kalmia sandy loam soil at Georgetown, Delaware. Yields were not significantly increased by the application of K fertilizer. Potassium soil test level was not significantly correlated with corn yield. Multiple extraction and leaching and changes in soil test K indicated that this soil has a K equilibrium which is reestablished sufficiently rapid to supply K to a growing corn crop.