Contribution of contrasting plant hierarchies to the response to N fertilizer in maize

The typical size structuring process that occurs as a consequence of intra-specific competition in maize promotes the appearance of contrasting plant hierarchies (i.e. dominated and dominant individuals). This process may become more intense under low nitrogen (N) availability. The alleviation of plant competition by N addition may reduce plant yield variability through a differential response to N in individuals of contrasting hierarchies. In this work, the response to N of dominated and dominant plants from stands with contrasting N supply (0 to 140-200kgNha-1) was examined on 11 experiments carried out in Paraná, Argentina (31°50'S; 60°31'W) in a broad range of growing conditions that included the variation of the year, genotype, plant population and sowing date. Our objectives were: (i) to evaluate the response to N in contrasting plant hierarchies of maize, (ii) to quantify the contribution of dominated and dominant plants to the response to N of the overall stand, and (iii) to study the effect of N on relationships between plant hierarchies and stand variability. Response to N of yield per plant was associated with biomass per plant in non-fertilized controls, tending to be higher in plants with low biomass. The response to N of yield per unit area (i.e., considering all individuals of the stand) was related to the response to N of dominant and dominated plants (P50-60%), dominant plants had a considerable lower response than dominated plants, whereas at a lower level of response (<30%), the contribution of contrasting plant hierarchies was similar. In stands with similar plant biomass between hierarchies, the differences in the response to N between plant types tended to be negligible. The coefficient of variation of yield per plant was reduced (P<0.05) by effect of N in 4 out of 11 experiments, although it tended to be consistently lower in fertilized treatments. When the differences between the biomass of dominated and dominant plants were ample we found the highest response to N at the stand level, as a result of the higher increase in grain yield per plant in dominated plants than in dominant ones. The response to N in each plant hierarchy was differentially associated with increases in shoot biomass, harvest index, kernel number per plant and kernel weight.Fil: Caviglia, Octavio Pedro. Universidad Nacional de Entre Ríos; Argentina. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Melchiori, Ricardo José Miguel. Instituto Nacional de Tecnología Agropecuaria; Argentin

Addition of cover crop residues and organic amendments: effect on nitrifiers and cellulolytic microorganisms

El aporte de residuos de cultivos de cobertura (CC) y enmiendas orgánicas al suelo, como cama de pollo y gallinaza, es una fuente de C y N qué a través de su descomposición regula la actividad y abundancia de los microorganismos del suelo. El objetivo fue estudiar cómo se ven afectadas la actividad y la abundancia de los microorganismos nitrificadores y celulolíticos, en dos profundidades de suelo, cuando se aportan residuos aéreos de CC y enmiendas orgánicas de diferente composición en superficie y en ausencia de cultivos. El experimento se llevó a cabo durante dos años consecutivos en la EEA Paraná del INTA, Argentina (−31° 50,9′ S; −60°32,3′ W), los tratamientos fueron adición de residuos aéreos de trigo (Triticumaestivum L.) y melilotus (Melilotus albus Medik.), cama de pollo y gallinaza. Se determinó la humedad, actividad y abundancia de microorganismos nitrificadores y celulolíticos en muestras de suelos colectadas a 0-0,05m y a 0,05-0,2m de profundidad en diferentes momentos. La actividad nitrificadora fue de 0.01-0,54mg NO3 g-1 (0-0,05m) y de 0,001-0,18mg NO3 g-1 (0,05-0,20m), la abundancia nitrificadora en promedio fue de 5,25 log g-1 en ambas profundidades. Por otra parte, la actividad celulolítica mostró diferencias entre profundidades (P<0,0001) con valores medios de 0,07 mg g-1 (0-0,05m) y 0,05 mg g-1 (0,050,2m) y la abundancia de celulolíticos mostró diferencias significativas entre las profundidades (P<0,025) aunque con valores muy similares. Los aportes de residuos con baja relación C:N, se asociaron fuertemente al nitrato inicial y a la actividad nitrificadora. En contraste, el residuo de trigo, con alta relación C:N, se asoció con la glucosa inicial, abundancia de celulolíticos y nitrificadores y actividad celulolítica. Este trabajo permitió conocer el efecto de la adición de residuos aéreos de CC y enmiendas orgánicas, sin la intervención del aporte de las raíces, sobre los microorganismos celulolíticos y nitrificadores.The addition of cover crops and organic amendments, such as poultry manure and poultry litter, is a source of C and N to the soil. Their decomposition regulates the activity and abundance of soil microorganisms. Our objective was to study the effect of cover crops and organic amendment additions, applied on soil surface and without the presence of a living vegetal cover, on the abundance and activity of nitrifiers and cellulolytic microorganisms . We conducted an experiment during two consecutive years in Paraná, Argentina (−31° 50,9′ S; −60°32,3′ W). Treatments included the addition of organic amendments (composted poultry litter and poultry manure) and cover crops residues [wheat (Triticum aestivum L.) and white sweet clover (Melilotus albus Medik.)]. Soil water content, activity and abundance of nitrifiers and cellulolytic microorganisms were determined on soil samples taken at two depths (0-0.05m and 0.05-0.20m). The activity of nitrifiers was 0,01-0,54mg NO3 g-1 (0-0.05m) and the 0,001-0,18mg NO3 g-1 (0.05-0.20m), the average abundance of nitrifiers was 5,25 log g-1 at both depths, whereas cellulolytic activity showed differences between depths (P <0,0001) with average values of 0,07 mg g-1 (0-0,05m) and 0,05 mg g-1 (0,05-0,2m) and the abundance of cellulolytic showed significant differences between the depths (P <0,025) although with similar values. In contrast, wheat residues, with a high C: N ratio, were associated with initial glucose, abundance of cellulolytic and nitrifiers, and cellulolytic activity. This study allowed us to identify the effect of the addition of the aerial residue of CC and organic amendments, without the contribution of the roots, on the dynamics of cellulolytic and nitrifiers microorganisms.Fil: Gregorutti, Viviana Carolina. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Caviglia, Octavio Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Entre Ríos; Argentin

Impact of soybean cropping frequency on soil carbon storage in Mollisols and Vertisols

The high cropping frequency of soybean (Glycine max [L.] Merr.), mainly as a single annual crop, in the extensive agricultural systems of South America may adversely affect the soil organic carbon (SOC) storage, which may be different between soils depending on aggregation agents. The aim of this work was to evaluate the impact of the soybean cropping frequency on the SOC storage in different soil aggregate size classes in a Mollisol and in a Vertisol in the Northeastern Pampas of Argentina under no-tillage management. In each soil, the samples were collected at 0-5, 5-15 and 15-30 cm depths in eleven cropped and one uncropped fields. The number of months occupied with soybean in relation to the total number of months occupied with crops within crop sequences, over a 6-year period, was used to calculate the soybean cropping frequency. The SOC stocks in equivalent soil mass, the SOC concentration both in the whole sample and in different aggregate size classes, and the stratification ratio of the SOC stock and of the SOC concentration were determined. The increase in soybean cropping frequency reduced the SOC stock in both soils at 0-5 cm, and in the Vertisol at 5-15 and 0-30 cm but the change was evident only between the cropped and the uncropped situation. A decrease in soybean cropping frequency resulted in a higher amount of macroaggregates (> 250 um), a higher SOC concentration and a higher stratification ratio in the Mollisol at 0-5 cm, whereas in the Vertisol the soybean cropping frequency did not affect the stratification ratio or the aggregate distribution in any size class. The increase in soybean cropping frequency reduced SOC storage only in macroaggregates (> 250 µm) in both soils at 0-5 cm, particularly in the largest macroaggregates (> 2000 µm), and more in the Mollisol than in the Vertisol. Our results show that a high soybean cropping frequency may severely affect the SOC storage in the Mollisol, and suggest that in the Vertisol this effect may lead to a reduction in the SOC storage in the long term.Fil: Novelli, Leonardo Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; ArgentinaFil: Caviglia, Octavio Pedro. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Entre Ríos; ArgentinaFil: Melchiori, R. J. M.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentin

Land use intensity and cropping sequence effects on aggregate stability and C storage in a Vertisol and a Mollisol

The relevant change in land use due mainly to the rapid expansion of soybean cropping towards areas traditionally occupied for livestock purposes or with native grasslands of South America may have negative consequences on soil organic carbon (SOC) storage and aggregate stability, although the effect may be different between soils with contrasting aggregation agents. The aim of our work was to assess the impact of the land use, measured as the intensification and/or frequency of a given crop, on SOC storage and aggregate stability in two soils differing in their main agents of aggregation. The study was conducted in a Mollisol and a Vertisol of Argentina. Eleven cropped fields (agricultural and crop-pasture rotation) under no-tillage and one uncropped situation (pristine native grassland) were selected in each soil type. The fraction of annual time with plant cover (as a measure of the intensification in the land use) and the frequency of a given crop in the cropping sequence over a 6-year period were calculated. Undisturbed soil samples were collected from each soil at 0-5, 5-15 and 15-30 cm depths. The SOC stocks in equivalent soil mass were calculated using the native grassland as the baseline system. Aggregate stability was evaluated using a method that involved three pretreatments: fast wetting, stirring after prewetting and slow wetting. The intensification improved the aggregate stability in the Mollisol, whereas a low impact of land use on aggregate stability was recorded in the Vertisol. Overall, both the intensification sequence index and the soybean cropping frequency were the best indexes to evaluate the impact of land use on aggregate stability and SOC storage, mainly in the Mollisol. The stirring after prewetting pretreatment was mainly associated with SOC concentration in the Mollisol, appearing as a method with high potential capacity to discriminate land use in the Mollisol, in which the SOC is the main aggregation agent. In contrast, the slow wetting pretreatment was more appropriate to evaluate the impact of land use in the Vertisol. The approach used to evaluate the land use, which included agricultural lands, crop-pasture rotation and native grasslands, evaluated through indexes of occupation with plant cover, was more suitable for the Mollisol than for the Vertisol. This reveals that the evaluation of land use through several indexes should be based on the soil typeFil: Novelli, Leonardo Esteban. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Caviglia, Octavio Pedro. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Wilson, M. G.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Casal, M. C.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentin

Evaluation of Agricultural Production Systems Simulator (APSIM) as yield predictor of Panicum virgatum and Miscanthus x giganteus in several US environments

Simulation models for perennial energy crops such as switchgrass (Panicum virgatum L.) and Miscanthus (Miscanthus x giganteus) can be useful tools to design management strategies for biomass productivity improvement in US environments. The Agricultural Production Systems Simulator (APSIM) is a biophysical model with the potential to simulate the growth of perennial crops. APSIM crop modules do not exist for switchgrass and Miscanthus, however, re‐parameterization of existing APSIM modules could be used to simulate the growth of these perennials. Our aim was to evaluate the ability of APSIM to predict the dry matter (DM) yield of switchgrass and Miscanthus at several US locations. The Lucerne (for switchgrass) and Sugarcane (for Miscanthus) APSIM modules were calibrated using data from four locations in Indiana. A sensitivity analysis informed the relative impact of changes in plant and soil parameters of APSIM Lucerne and APSIM Sugarcane modules. An independent dataset of switchgrass and Miscanthus DM yields from several US environments was used to validate these re‐parameterized APSIM modules. The re‐parameterized modules simulated DM yields of switchgrass [0.95 for CCC (concordance correlation coefficient) and 0 for SB (bias of the simulation from the measurement)] and Miscanthus (0.65 and 0% for CCC and SB, respectively) accurately at most locations with the exception of switchgrass at southern US sites (0.01 for CCC and 2% for SB). Therefore, the APSIM model is a promising tool for simulating DM yields for switchgrass and Miscanthus while accounting for environmental variability. Given our study was strictly based on APSIM calibrations at Indiana locations, additional research using more extensive calibration data may enhance APSIM robustness.Fil: Ojeda, Jonathan Jesus. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Volenec, Jeffrey J.. Purdue University; Estados UnidosFil: Brouder, Sylvie M.. Purdue University; Estados UnidosFil: Caviglia, Octavio Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; ArgentinaFil: Agnusdei, Mónica G.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce; Argentin

Calibration of critical thresholds of soil available nitrogen for late-sown maize in Entre Rios province, Argentina

Con el fin de estabilizar los rendimientos de maíz (Zea mays L.), evitando la coincidencia de la floración con momentos de mayor déficit hídrico típicos de las siembras tempranas, la superficie de maíz tardío (MT) en Entre Ríos se ha incrementado notoriamente desde 2010. El objetivo del presente trabajo fue desarrollar una metodología de diagnóstico para recomendar la fertilización nitrogenada en MT en Entre Ríos, a partir del nitrógeno (N) disponible en el suelo + fertilizante (Nd). El trabajo se realizó sobre doce experimentos de fertilización nitrogenada en MT, conducidos durante dos campañas. Cuando se consideraron todos los experimentos, no hubo asociación entre el Nd y el rendimiento, producto de la variabilidad encontrada en la respuesta a N entre localidades. Debido a dicha variabilidad, se trabajó con el conjunto de las localidades utilizando el rendimiento relativo (RR). Los modelos lograron un mejor ajuste realizando el muestreo de suelo en presiembra (PS) que en V6. En PS, el ajuste no varió por modificar la profundidad de muestreo (0-20, 0-40 o 0-60 cm). El modelo que utilizó el RR mejoró el ajuste con respecto al modelo que utilizó el rendimiento y permitió obtener un único umbral de 165 kg Nd ha-1 a 0-60cm. Sin embargo, la utilización de un solo modelo puede llevar a recomendaciones incorrectas al no considerar distintos niveles de rendimiento. En efecto, los modelos que tuvieron en cuenta el ambiente, i.e. el rango de rendimientos obtenidos, difirieron en el umbral obtenido. Se definieron ambientes de menos de 6000 kg ha-1, 6000 a 9000 kg ha-1 y más de 9000 kg ha-1, para los cuales los umbrales de Nd (0-20 cm) fueron de 93; 102 y 108 kg N ha-1 y la eficiencia de uso del Nd fue de 13; 21 y 26 kg grano kg N-1, respectivamente.Since 2010, late-sown maize (MT) area in Entre Rios Province, Argentina has noticeably increased, in order to stabilize grain yields avoiding the coincidence of flowering with water deficit periods, which are typical in early sowings. We aimed to develop a methodology to recommend N fertilization in MT for the Entre Ríos Province, considering available N (soil N + fertilizer) (Nav). Twelve experiments of N fertilization were carried-out during two growing seasons. Owing wide yield variability among locations, no association between yield and Nav was detected, when all the locations were pooled. To deal with this variability, models considering Relative Yield (RR) can be alternatively used. Models considering soil sampling at pre-sowing (PS) have a better fit than those with soil sampling at V6. In PS, the fit of the model did not change across soil depth sampling (0-20, 0-40 or 0-60 cm). Using RR, fit of the model was improved and it allowed obtain a unique threshold of Nav (0-60 cm) of 165 kg Nav ha-1. However, since there are no single thresholds for all the environments, models considering yield-environment level could be more adequate. We defined yield-environments of: less than 6000 kg ha-1, 6000 to 9000 kg ha-1 and more than 9000 kg ha-1, with Nav (0-20 cm) thresholds of 93; 102 y 108 kg N ha-1 and N use efficency of 13; 21 y 26 kg grain kg Nav-1, respectively.Fil: Diaz Valdez, Santiago T.. Bayer Cropscience Sociedad Anonima; ArgentinaFil: Garcia, Fernando Oscar. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Caviglia, Octavio Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Entre Ríos; Argentina. International Plant Nutrition Institute; Argentina. Monsanto Argentina SAIC. Equipo de Desarrollo Tecnológico; Argentin

¿Cómo decidir la fertilización nitrogenada en maíz en escenarios de incertidumbre?

La producción de maíz en Entre Ríos, se ha incrementado en los últimos años, impulsada, en parte, por cambios en las políticas económicas que permitieron que mejore su competitividad respecto al cultivo de soja. El incremento del área de siembra del cultivo de maíz es un aspecto clave que contribuye con la sustentabilidad de los agro ecosistemas, respondiendo además a satisfacer la creciente demanda local impulsada por las cadenas de producción animal. Sin embargo, la diferencia nutricional de los suelos condiciona los rendimientos alcanzables, y para trabajar bajo escenarios climáticos inciertos, como los pronosticados para el ciclo agrícola 2022/2023, resulta indispensable el uso de herramientas sólidas de análisis para el soporte de decisiones en la fertilización.Fil: Melchiori, Ricardo José Miguel. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; ArgentinaFil: Maltese, Nicolás Elías. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Correndo, A.A.. Kansas State University; Estados UnidosFil: Novelli, Leonardo Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Caviglia, Octavio Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; Argentin

¿Cómo decidir la fertilización nitrogenada en maíz en escenarios de incertidumbre?

La producción de maíz en Entre Ríos, se ha incrementado en los últimos años, impulsada, en parte, por cambios en las políticas económicas que permitieron que mejore su competitividad respecto al cultivo de soja. El incremento del área de siembra del cultivo de maíz es un aspecto clave que contribuye con la sustentabilidad de los agro ecosistemas, respondiendo además a satisfacer la creciente demanda local impulsada por las cadenas de producción animal. Sin embargo, la diferencia nutricional de los suelos condiciona los rendimientos alcanzables, y para trabajar bajo escenarios climáticos inciertos, como los pronosticados para el ciclo agrícola 2022/2023, resulta indispensable el uso de herramientas sólidas de análisis para el soporte de decisiones en la fertilización.Fil: Melchiori, Ricardo José Miguel. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; ArgentinaFil: Maltese, Nicolás Elías. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Correndo, A.A.. Kansas State University; Estados UnidosFil: Novelli, Leonardo Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Caviglia, Octavio Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; Argentin

Temperature-Driven Developmental Modulation of Yield Response to Nitrogen in Wheat and Maize

Nitrogen management is central to the economic and environmental dimensions of agricultural sustainability. Yield response to nitrogen fertilisation results from multiple interacting factors. Theoretical frameworks are lagging for the interaction between nitrogen and air temperature, the focus of this study. We analyse the relation between yield response to nitrogen fertiliser and air temperature in the critical period of yield formation for spring wheat in Australia, winter wheat in the US, and maize in both the US and Argentina. Our framework assumes (i) yield response to nitrogen fertiliser is primarily related to grain number per m2, (ii) grain number is a function of three traits: the duration of the critical period, growth rate during the critical period, and reproductive allocation, and (iii) all three traits vary non-linearly with temperature. We show that “high” nitrogen supply may be positive, neutral, or negative for yield under “high” temperature, depending on the part of the response curve captured experimentally. The relationship between yield response to nitrogen and mean temperature in the critical period was strong in wheat and weak in maize. Negative associations for both spring wheat in Australia and winter wheat with low initial soil nitrogen ( 120 kg N ha-1) that favoured grain number and compromised grain fill, the relation between yield response to nitrogen and temperature was positive for winter wheat. The framework is particularly insightful where data did not match predictions; a non-linear function integrating development, carbon assimilation and reproductive partitioning bounded the pooled data for maize in the US and Argentina, where water regime, previous crop, and soil nitrogen overrode the effect of temperature on yield response to nitrogen fertilisation.Fil: Sadras, Victor O.. University of Adelaide; Australia. South Australian Research And Development Institute; AustraliaFil: Giordano, Nicolas. Kansas State University; Estados UnidosFil: Correndo, Adrian. Kansas State University; Estados UnidosFil: Cossani, C. Mariano. University of Adelaide; Australia. South Australian Research And Development Institute; AustraliaFil: Ferreyra, Juan M.. No especifíca;Fil: Caviglia, Octavio Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Entre Ríos; ArgentinaFil: Coulter, Jeffrey A.. University of Minnesota; Estados UnidosFil: Ciampitti, Ignacio Antonio. Kansas State University; Estados UnidosFil: Lollato, Romulo P.. Kansas State University; Estados Unido

Predicting soil test phosphorus decrease in non-P-fertilized conditions

Monitoring the availability of phosphorus (P) in soil under continuous cropping facilitates finding deficiency in crops and contributes to improving crop growth and nutrient management models. Soil P availability for crops is usually estimated by soil test P (STP), such as Bray-1. This is widely used in the Americas. The relationship between the decrease of STP Bray-1 and cumulative removal of P was evaluated in non-P-fertilized areas in long-term studies. This removal was the sum of annual P removal over the study period as P exported in grains/crop outside the soil. The objectives were to: (a) quantify changes in STP as a function of cumulative P removal, (b) assess the relationship between relative decrease rate of STP and soil variables as well as annual removal of P by crops, and (c) develop a model to predict decrease of STP Bray-1. Exponential decay functions were used to describe annual cumulative removal of P and STP from soil over time for 12 long-term studies where no addition of P fertilizer was carried out. Changes in the relative rate of decrease of STP, relative to the initial STP Bray-1 value at the onset of the experiment, were predicted by the ratio of soil organic matter to clay and silt and the average annual P removal by exponential decay (R2adj = 0.64; RMSE = 3.2 mg kg−1). We propose this predictive model as suitable to provide estimates of the relative decrease rate of STP by Bray-1 and thereby improve management of P for optimizing crop yield. Highlights: STP Bray-1 decrease and cumulative P removal were related by exponential decay functions. Relative decrease rate of STP Bray-1 was related to SOM/(clay+silt) ratio and annual P removal. A predictive model of the relative decrease rate of STP Bray-1 was fitted and validate. Our model is a useful tool to help predict soil P availability and nutrient management.Fil: Appelhans, Stefania Carolina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Universidad Nacional de Entre Ríos; Argentina. Kansas State University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Carciochi, Walter Daniel. Kansas State University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Correndo, Adrian. Kansas State University; Estados UnidosFil: Gutiérrez Boem, Flavio Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales; ArgentinaFil: Salvagiotti, Fernando. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Oliveros; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garcia, Fernando Oscar. International Plant Nutrition Institute; ArgentinaFil: Melchiori, Ricardo J.M.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; ArgentinaFil: Barbagelata, Pedro Aníbal. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Universidad Nacional de Entre Ríos; ArgentinaFil: Ventimiglia, Luis A.. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Buenos Aires Norte. Estacion Experimental Agropecuaria Pergamino. Agencia de Extension Rural 9 de Julio.; ArgentinaFil: Ferraris, Gustavo Nestor. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Pergamino; ArgentinaFil: Vivas, Hugo S.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Caviglia, Octavio Pedro. Universidad Nacional de Entre Ríos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ciampitti, Ignacio Antonio. Kansas State University; Estados Unido