Phosphorus Corn Research Articles

Determining the nutritional values of new corn varieties on pigs and broilers.

The objective of this study was to evaluate the nutritional values of three new corn varieties (high-iron corn, cadmium-resistant corn, low-phytate phosphorus corn) cultivated with molecular marker-assisted selection breeding technique fed to growing pigs and broilers. Exp. 1 was conducted to compare the nutritional values of high-iron corn, high-chromium corn, low-phytate phosphorus corn and conventional corn fed to growing pigs based on a 15 × 2 Youden square design. Exp.2 was conducted to compare the nutritional values of high-iron corn, low-phytate phosphorus corn and conventional corn fed to broilers based on a completely randomized design. Parameters including nutrient digestibility, available energy and amino acids, and mineral deposition were measured. The results shows that the iron content in the high-iron corn and the cadmium content in the cadmium-resistant corn were 29.608 mg/kg and 0.0057 mg/kg, respectively, both were greater than those in the other three kinds of corns. When fed to growing pigs, the neutral detergent fiber digestibility of the high-iron corn group was lower than that of the conventional corn group (p < 0.05), and the acid detergent fiber digestibility of the high-iron group and the low-phytate phosphorus corn group was lower than that of the conventional corn group (p < 0.01). In addition, the digestible energy value of the high-iron corn in growing pigs was lower than that of the conventional corn (p < 0.05). When fed to broilers, it was observed that the tibia length of the low-phytate phosphorus corn group and the high-iron corn group was lower than that of the conventional corn group (p < 0.05). Moreover, the iron emission in feces of broilers fed the low-phytate phosphorus corn was lower than those fed the conventional corn and the high-iron corn (p < 0.05). In conclusion, modern breeding techniques could provide new plant ingredients which have potential benefits to pig and broiler production, but the comprehensive effects may be better when applied to growing pigs considering growth performance and environment effects. The breeding techniques related to the current study rarely changed the available energy values of the corn in growing pigs and broilers.

Agronomic efficiency of rock phosphates used alone or associated with soluble source of phosphorus for corn and common bean crops cultivated in succession under no-tillage and irrigated system.

Agronomic efficiency of rock phosphates used alone or associated with soluble source of phosphorus for corn and common bean crops cultivated in succession under no-tillage and irrigated system.

Careful Placement Allows Manure to Replace Starter Phosphorus in Corn

AbstractMost crops in northern climates benefit from a boost from phosphorus to get started. Previous studies have looked into whether manure could replace mineral phosphorus starter fertilizer in corn, but results have been iffy on how exactly to do this. Some research has even indicated manure can be detrimental to corn roots and growth. A new article published in Agronomy Journal confirms that manure can replace starter phosphorus fertilizer in corn, but farmers must be careful in where and how it’s applied. Earn 0.5 CEUs in Nutrient Management by reading the article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/944.

On‐farm corn phosphorus response reveals importance of soil testing

Core Ideas Increased soil test P values above the critical threshold reduces the likelihood of grain yield response to P fertilizer application. Soil test P critical concentrations of 14 ppm indicated no change from Tri‐State Soil Fertility recommendations. Shallower soil sampling (0–2 inches) did not improve relationship between soil test P concentration and relative grain yield.

Additivity of apparent and standardised ileal digestibility of phosphorus in corn and canola meal mixed diets; basal endogenous loss of phosphorus responses to phytase and age in broiler chickens

ABSTRACT 1. The additivity of apparent ileal digestibility (AID) and standardised ileal digestibility (SID) of phosphorus (P) in mixed diets containing corn and canola meal (CCM) with or without phytase supplementation and the impact of age on the basal ileal endogenous loss (BEL) of P were investigated in broiler chickens. 2. Treatments were arranged as a 2 × 3 × 2 factorial with two ages (13 d or 21 d post hatching), three diets (corn, canola meal, or CCM), and two phytase levels (0 or 1,000 FYT/kg diet) in a randomised complete block design. There were eight or six birds per cage at 13 d and 21 d of age, respectively, and six replicate cages per treatment, with a total of 588 birds. A P-free diet (PFD) treatment was included at each age to determine the basal endogenous loss (BEL) of P. 3. Birds were fed a commercial starter diet from d 1 to d 10 or d 18 and then fed the experimental diets for 3 d until d 13 or d 21, respectively. Predicted digestibility values calculated from the individual feed ingredients were used to test additivity in the mixed diets. Chromium oxide was included in diets as an indigestible marker. 4. The ileal digesta, collected from birds at d 13 or d 21, was used to determine nutrient digestibility. 5. The AID and SID of P at d 13 was higher (P < 0.01) when compared with older birds at d 21, regardless of dietary phytase supplementation. Regardless of age or phytase supplementation, AID and SID of P were additive, as there were no differences between predicted and determined values in the mixed diets. The BEL of P (g/kg DM intake) in birds at d 13 was higher (P < 0.05) than birds at d 21 (0.197 vs. 0.159). 6. In conclusion, age had an impact on the BEL of P and the utilisation of minerals in the diets. The apparent and standardised ileal digestibility of P in the mixed diet containing corn and canola meal were additive, regardless of age or phytase supplementation.

Sweet Corn Phosphorus Uptake from Sandy Soil Amended with Anaerobically-digested Manure

ABSTRACT Anaerobic digester development on dairy, poultry, and swine confined animal feeding operations (CAFOs) reduce manure storage, produce energy and are poised to supply a variety of nutrient-rich materials. Field experiments were conducted in the Columbia Basin of South-Central Washington to evaluate the yield response and phosphorous (P) use efficiency of sweet corn (Zea mayes convar. saccharata cv. Sheba) to the application of P from anaerobic-digested manures. Treatments consisted of the application of 0, 10, 20, 40 kg P ha−1 from five sources, three from anaerobic digesters (AD); AD-dairy P fine solids; AD centrifuged poultry solids; and AD dairy-derived struvite-P compared to a commercial poultry fertilizer, commercial mono-ammonium phosphate, and a non-amended control. Sweet corn yields were not significantly different among P amendments or rates of application but were different between years and were greater than the No-P treatment in 2014. Phosphorus recovery efficiency defined as that percentage of applied P recovered by sweet corn averaged 138% among treatments receiving 10 kg P ha−1 and declined to 57% for higher rates of poultry materials and the commercial mono-ammonium phosphate (MAP) in 2013 and declined 50% in 2014 due to lower yields. Although yield was not different the uptake of P among treatments was significantly greater than the unfertilized control. The lack of yield differences among rates of P applied indicates that P was not limiting yield and suggests that under these production conditions the application of 10 kg P ha−1 of any of the amendments was sufficient. Abbreviations: AD: anaerobic digestion; ADD: anaerobic-digested dairy manure; ADP: anaerobic digested poultry manure; ADS: anaerobic-digested struvite; DM – dry matter; MAP – mono ammonium phosphate; PBP a commercial poultry fertilizer; PRD: percent P recovery efficiency difference method; PRB: percent P recovery balance method; PUE: Phosphorus use efficiency; AUE – Agronomic utilization efficiency.

Intrinsic phytase in hybrid rye increases the digestibility of phosphorus in corn and soybean meal in diets fed to growing pigs.

An experiment was conducted to test the hypothesis that inclusion of hybrid rye in diets containing corn and soybean meal (SBM) without or with microbial phytase improves the apparent total tract digestibility (ATTD) and the standardized total tract digestibility (STTD) of P because of the intrinsic phytase activity in hybrid rye. Forty-eight growing barrows (initial body weight: 39.5 ± 7.7 kg) were allotted to six diets. A basal diet containing corn and SBM; a rye-based diet; and a diet containing corn, SBM, and rye were formulated. Each diet was formulated without and with microbial phytase (500 units/kg of diet) for a total of six diets. Fecal samples were collected for 4 d following a 5-d adaptation period according to the marker-to-marker procedure. Results indicated that no interactions between diets and concentration of phytase were observed for any of the response criteria measured. The ATTD and STTD of P and the ATTD of Ca differed (P < 0.05) among diets, but regardless of diet, the concentration of P in feces was reduced (P < 0.05) by adding microbial phytase to the diets. As a consequence, microbial phytase increased (P < 0.05) ATTD and STTD of P, and the ATTD of Ca was also increased (P < 0.05) by the use of microbial phytase. Measured values for the ATTD and STTD of P in the diets containing corn, SBM, and hybrid rye without or with phytase were greater (P < 0.05) than values that were predicted based on the ATTD and STTD of P for the corn-SBM and the hybrid rye diet. The observation that STTD predicted from the individual ingredients underestimated the STTD of P in the mixed diet indicates that the intrinsic phytase in hybrid rye resulted in increased digestibility of the P in the corn and SBM included in the corn-SBM-hybrid rye diet. In conclusion, microbial phytase increased the ATTD and STTD of P and the ATTD of Ca regardless of feed ingredients used in diets fed to pigs. In addition, the intrinsic phytase from hybrid rye increased the ATTD and STTD of P in corn and SBM.

Do we need to apply additional phosphorus for corn succeeding sugarbeet?

AbstractSupply of adequate P is critical at the early growth stages of corn (Zea mays L.), particularly under a cold environment like the northern Great Plains. The mutualistic relationship between arbuscular mycorrhizal fungi (AMF) and corn roots is responsible for supplying P. However, colonies of AMF drastically decline when corn follows a non‐host crop like sugarbeet (Beta vulgaris L.) in rotation. Field experiments were conducted at two sites during 2018 and 2019 seasons to determine the corn grain yield response to six P management practices, (a) without P, (b) recommended P, (c) P2O5 at the rate of 112 kg ha−1, (d) starter at the rate of 13.7 kg P2O5 ha−1, (e) commercial mycorrhizal inoculant, and (f) starter and mycorrhizal inoculant. Corn grain yield did not respond to P application across 4 site‐years. Application of 112 kg P2O5 ha−1 had significantly higher grain yield (15.6 Mg ha−1) than mycorrhizal inoculant (13.5 Mg ha−1) only at one site in 2018. Lowest soil available P was observed with only mycorrhizal inoculant. For one site, AMF population was significantly reduced under without P (0.79 μmol kg−1 soil) than recommended P application (1.79 μmol kg−1 soil). Higher than recommendation P rate, commercial mycorrhizal inoculant and starter P did not increase grain yield over without P application.

Crescimento e acúmulo de fósforo em milho sob doses de fosfato radicular e fosfito via foliar

O uso eficiente de fósforo (P) na agricultura tem sido o foco principal das pesquisas com este macronutriente. Os fosfitos, que têm sido considerados estimulantes de plantas, podem contribuir para aumentar a eficiência do uso de P pelo milho. Objetivou-se avaliar a influência do fosfito via foliar sobre o crescimento e acúmulo de fósforo de milho na fase inicial de crescimento sob doses de P. Um experimento foi instalado em delineamento inteiramente casualizado, em esquema fatorial 5 x 2 com quatro repetições. Aos 45 dias após o plantio foram avaliadas a altura de planta e diâmetro de caule, massa seca de parte aérea, caule e raízes, teores, acúmulo e P a eficiência de utilização de P (EUP). A adubação fosfatada do milho, cultivado em Luvissolo crômico no estádio inicial é fundamental para incrementar seu crescimento e a produção de massa seca e acúmulo de P. O fosfito aplicado via foliar não produziu benefício adicional no crescimento, produção de biomassa ou nutrição fosfata do milho, mas aumentou a EUP na dose intermediária (200 mg dm-3) deste nutriente.

PSVIII-6 The small intestinal responses in the determination of true digestibility and the endogenous outputs of phosphorus in corn for growing pig using the regression analysis technique

Abstract It is of important methodological considerations to understand how the small intestine would respond to feeding of a series of assay diets deficient in gradient levels of phosphorus (Pi) associated with corn in growing pigs by the regression analysis technique (TRAT). A total of 48 barrows, with an average initial BW 32 kg, were randomly assigned to 6 grower pig diets and were fed close to ad libitum for 10 d, with 8-d adaptation and 2-d collection fecal samples, according to a randomized complete block design. Six cornstarch-based diets, containing 6 levels of Pi at 1.3, 1.9, 2.0, 3.6, 3.4 and 4.0 g/kg DMI, were formulated from corn. The gut permeability marker of D-mannitol was fed 0.30 g/kg BW at 4 h, prior to be sacrificed for sampling. ADG and the apparent ileal DM digestibility were linearly affected (P &amp;lt; 0.05); however, the ADFI, feed conversion ratio, the apparent fecal DM digestibility, transcellular gut permeability and the jejunal alkaline phosphatase kinetics were not affected (P &amp;gt; 0.05) by the increasing dietary levels of corn inclusion. There were linear relationships (P &amp;lt; 0.05), expressed as g/kg DMI, between the apparent ileal and fecal digestible Pi and the total intake of dietary Pi, suggesting that true ileal and fecal Pi digestibility (33.3±4.7 vs. 52.7±3.8%); and the endogenous Pi outputs (0.37±0.12 vs. 0.60±0.09, g/kg DMI) associated with corn could be estimated by the TRAT. Our results have shown that the intestinal physiological functions were not affected in the grower pigs fed on a series of test diets that were deficient in gradient levels of multiple assay nutrients, including macro-minerals, crude protein and amino acids supplied from the testing corn, for a period of 10 d, in the determination of corn-specific true digestibility and the endogenous outputs of Pi by the TRAT.

Cholesterol, Yield, Tibia and Clavicle Ash of Broilers fed High Available Phosphorus Corn and/or Phytase with/without Alum Litter Treatment

Cholesterol, Yield, Tibia and Clavicle Ash of Broilers fed High Available Phosphorus Corn and/or Phytase with/without Alum Litter Treatment

Retrofit Process Development for Phytate Extraction from Corn-Ethanol Coproducts Using Industrial Anion-Exchange Resins

Phytate, the principal storage form of phosphorus in corn, is found to remain as a significant portion of phosphorus in the corn-ethanol coproducts streams. This poses concerns over poor digestion of these coproducts by monogastric animals and subsequent environmental issues on phosphorus. An ion-exchange-based process was developed to extract the phytate from thin stillage, which was selected as the influent based on the inositol phosphate distribution conducted on different corn-ethanol coproducts. Commercial industrial resins (IRA-93, IRA-68, IRA-900, IRA-400, and IRA-402) were characterized and screened for the phytate adsorption, specificity and capacity. Different types of eluents (NaOH, NaCl, NaHCO3, HCl, and NH4OH) were tested to evaluate the desorption capacity in all the six resins. Phytate-P isotherms and kinetics of the adsorption process, breakthrough profile on IRA-900 column and phytate elution curves were presented. This process yields a phytate-rich solution (11 g L–1), which is 25-fold c...

Potential Farmer Adoption of High Available Phosphorus Corn over a Three-year Period

Corn containing high levels of available phosphorus (HAP) allows poultry to use more of the phosphorus they consume and could potentially reduce contamination of water from run-off. This study uses a conjoint analysis survey of Delmarva corn growers to model adoption of hypothetical HAP varieties over a three-year period. An optimal variety has a low technology fee and yield drag and a high harvest premium. Adoption of HAP corn increases during the period although growers’ tolerance of technology fees and yield drags diminishes over time. Adoption is further affected by farm size, farmer age, and the portion of income from corn.

Factors affecting arsenic and copper runoff from fields fertilized with poultry litter.

Arsenic (As) and copper (Cu) runoff from fields fertilized with poultry litter has received increasing attention in recent years, although it is not known if heavy metal runoff from poultry litter poses a significant threat to the environment. The objective of this study was to determine the main factors affecting As and Cu concentrations in runoff water from pastures receiving poultry litter applications. Rainfall simulation studies were conducted to determine the effects of the following treatments on metal runoff: (i) aluminum sulfate (alum) additions, (ii) diet modification using phytase or high available phosphorus corn, (iii) fertilizer type, (iv) poultry litter application rate, and (v) time until the first runoff event occurs after poultry litter application. Results showed that alum additions to poultry litter significantly decreased As and Cu concentrations in runoff water. Copper concentrations were highest in runoff from poultry litter from birds fed phytase diets compared with other diets; however, this effect may have been a result of wet storage conditions rather than diet. Triple superphosphate applications resulted in the lowest heavy metal concentrations in runoff water among all fertilizer treatments, while normal poultry litter resulted in the highest concentrations. Arsenic and Cu concentrations increased in runoff water as poultry litter application rates increased and decreased with increasing time until the first runoff event. These data indicate that adding alum to poultry litter, a cost-effective best management practice, which also results in lower P runoff and ammonia emissions, may also be an effective tool in reducing metal runoff.

Measurement of true ileal digestibility and total tract retention of phosphorus in corn and canola meal for broiler chickens

The study reported herein was conducted to determine and compare the nonphytate P, digestible P, and retainable P contents of corn and canola meal for broiler chickens. Four semipurified diets were formulated from each of ingredient to contain graded concentrations of nonphytate P. The experiment was conducted as a randomized complete block design with 4 weight blocks of 8 cages each (6 birds per cage). A total of 192 broilers (Ross 308), 21 d old, were assigned to the 8 test diets. Ileal digestibility and total tract retention coefficients of P were determined by the indicator and total collection methods, respectively, and linear regression method was used to determine the true P digestibility and true P retention coefficients. The apparent ileal digestibility of P in corn was influenced (quadratic, P < 0.05) by increasing dietary nonphytate P concentrations, whereas P retention was unaffected (P > 0.05). The apparent ileal P digestibility in broilers fed diets based on canola meal was similar (P > 0.05) at different P concentrations. Phosphorus retention in broilers fed diets based on canola meal (linear, P < 0.01) decreased with increasing P concentrations. True ileal P digestibility and true P retention coefficients of corn were determined to be 0.676 and 0.632, respectively. The corresponding values for canola meal were 0.469 and 0.486, respectively. In both ingredients, the determined true ileal digestibility and total tract retention coefficients were not different (P > 0.05). Total P, nonphytate P, true digestible P, and true retainable P contents of corn were determined to be 2.5, 0.8, 1.7, and 1.6 g/kg (as received), respectively. The corresponding values for canola meal were 9.7, 2.8, 4.6, and 4.7 g/kg (as received), respectively. The present data demonstrated that the regression method can be successfully used to measure true P digestibility of low and high P feed ingredients and that both true ileal digestibility and retention coefficients are suitable to assess P availability in broilers.

True total-tract digestibility of phosphorus in corn and soybean meal for fifteen-kilogram pigs are additive in corn–soybean meal diet

The objective of this study was to verify the additivity of true total-tract P digestibility (TPD) in corn and soybean meal (SBM) for 15-kg pigs. Fifty-four barrows with an average initial BW of 14.7±1.6 kg were used in a randomized complete block design with a 3×2 factorial arrangement of 6 diets. Three P sources included corn, SBM, and their mixture at a ratio of 2:1. Each P source was provided at low or high level. The diets were fed for a 5-d adjustment period followed by a total collection period of 7 d with ferric oxide as a marker to determine the initiation and termination of fecal collection. The results showed the high P level of each P source increased (P<0.001) P intake, fecal P output, and digested P compared with the low P level. The respective apparent total-tract digestibility of P were 35.66 and 40.57% for low and high P levels in corn, 35.72 and 38.04% for low and high P levels in SBM, and 41.85 and 38.53% for low and high P levels in the corn-soybean meal mixture without significant difference between P levels within P sources. Regressing daily digested P against daily P intake, the TPD was estimated at 40.53, 35.96, and 37.52% for corn, SBM, and their mixture, respectively. The expected TPD in corn and SBM mixture was calculated to be 37.92% based upon the P contribution coefficient calculated to be 0.428 for corn and 0.572 for SBM. The determined TPD (37.52%) in the mixture was not statistically different from the expected (37.92%). In conclusion, the TPD in corn and SBM are additive in corn-soybean meal diet for pigs.

Effects of graded levels of microbial phytase on the standardized total tract digestibility of phosphorus in corn and corn coproducts fed to pigs1

An experiment was conducted to determine the influence of adding graded levels of microbial phytase to corn, distillers dried grains with solubles (DDGS), high-protein distillers dried grains (HP-DDG), and corn germ on the standardized total tract digestibility (STTD) of P. A second objective was to develop regression equations to predict the response of adding phytase to each of these ingredients. Four corn-based diets, 4 DDGS-based diets, 4 HP-DDG-based diets, and 4 corn germ-based diets were formulated. The 4 diets with each ingredient were formulated to contain 0, 500, 1,000, or 1,500 phytase units (FTU)/kg. A P-free diet was also formulated to determine basal endogenous losses of P. A total of 102 pigs (initial BW: 18.2 ± 2.1 kg) were individually housed in metabolism cages equipped with a feeder, a nipple drinker, and a screen floor that allowed for total collection of feces. Pigs were allotted to the 17 diets in a randomized complete block design with 6 replicate pigs per diet. Pigs were fed their respective diets for 12 d, and feces were collected quantitatively from d 6 to 11. Supplementation with 500, 1,000, or 1,500 FTU of microbial phytase/kg increased (linear, P < 0.01; quadratic, P < 0.05) the STTD of P in corn from 40.9 to 67.5, 64.5, and 74.9%, respectively, tended to increase (linear, P = 0.07) the STTD of P in DDGS from 76.9 to 82.9, 82.5, and 83.0%, respectively, increased (linear, P < 0.01; quadratic, P < 0.05) the STTD of P in HP-DDG from 77.1 to 88.0, 84.1, and 86.9%, respectively, and increased (linear and quadratic, P < 0.01) the STTD of P in corn germ from 40.7 to 59.0, 64.4, and 63.2%, respectively. Regression equations were developed to calculate the STTD of P in corn and corn germ, and R(2) values were 0.63 and 0.79, respectively. However, for DDGS and HP-DDG, the R(2) values were only 0.20 and 0.36, respectively, and these equations were, therefore, not considered adequate to predict the STTD of P. In conclusion, the increase in the STTD of P in corn and corn germ that is a result of microbial phytase can be predicted by regression equations, but microbial phytase has much less of an effect on the STTD of P in DDGS and HP-DDG and responses to addition of graded levels of phytase to these ingredients can, therefore, not be accurately predicted by regression equations.

Consumer Interest in Environmentally Beneficial Chicken Feeds: Comparing High Available Phosphorus Corn and Other Varieties

One source of phosphorous pollution in areas of high chicken production is runoff from fields using fertilizer from these operations. A potential solution is to feed chicken high available phosphorus (HAP) corn, reducing phosphorus in manure. This study examined consumer purchase likelihood of chickens fed HAP, created traditionally or through genetic modification, and other genetically modified (GM) corn including Bt and Roundup-ready. Survey results from the Delmarva Peninsula found considerable interest in non-GM HAP corn, although GM HAP corn was not typically viewed as more acceptable than other GM varieties. Overall, the marketplace appears open to products geared toward environmental benefits.

Biodisponibilidade relativa de fósforo em ingredientes com baixo teor de fitato determinada com base na mineralização óssea de frangos de corte

Quatrocentos e vinte pintos de corte Cobb 500, machos de 1 dia de idade, foram distribuídos aleatoriamente em 15 tratamentos com 4 repetições, em teste utilizando baterias (7 aves/gaiola), com duração de 21 dias, para determinar a biodisponibilidade relativa de fósforo (BRP) em três ingredientes, com duas características genéticas (baixo fósforo fítico ou convencional). Utilizou-se uma dieta basal semipurificada, à base de milho e farelo de soja, adicionada de cevada convencional, cevada com baixo fósforo fítico, milho convencional, milho com baixo fósforo fítico, farelo de soja convencional, farelo de soja com baixo fósforo fítico e de fosfato bicálcico em substituição ao amido de milho, de modo a fornecer 0,05 ou 0,10% de fósforo suplementar, totalizando 15 dietas [(3 × 2 × 2) + 3]. Semanalmente foram avaliados o peso vivo, o ganho de peso, o consumo de ração e a conversão alimentar por parcela experimental. Ao final do experimento, aos 21 dias de idade, foram abatidas 3 aves por unidade experimental para remoção das tíbias esquerdas para análise do conteúdo de cinzas ósseas. A biodisponibilidade de fósforo do milho, da cevada e do farelo de soja convencionais foram de 18,5; 50,9 e 34,4% respectivamente, enquanto, para a do milho, da cevada e do farelo de soja com baixo fósforo fítico foram de 93,5; 132,9 e 90,9% respectivamente. O consumo de ração, o ganho de peso e a mineralização óssea das aves alimentadas com as dietas com baixo fósforo fítico foram superiores aos daquelas alimentadas com as dietas convencionais.

AVALIAÇÃO DA DISPONIBILIDADE DE FÓSFORO NO SOLO PARA O MILHO PELOS MÉTODOS MEHLICH-1 E MEHLICH-3

Nos estudos de avaliação de metodologias de análise de solo, o fósforo tem sido o elemento mais estudado, fato este associado à complexidade da dinâmica do elemento no solo. A solução de Mehlich-1 vem sendo usada por muitos anos pelos laboratórios de análise de solo do Brasil, porém é um método que superestima a disponibilidade de fósforo no solo para as plantas em solo que receberam fosfato natural. A solução de Mehlich-3 foi proposta para solos ácidos e adubados com fosfato natural. Com o objetivo de comparar esses métodos na avaliação da disponibilidade de fósforo para as plantas de milho, foi conduzido um experimento com seis solos do estado do Rio Grande do Sul e cultivados com milho por 45 dias. Os coeficientes de determinação obtidos entre o fósforo absorvido pelas plantas de milho e o fósforo extraído foram: 0,88 para a solução de Mehlich-1 e 0,91 para a solução de Mehlich-3. As quantidades de fósforo extraído do solo pelas soluções tiveram alto grau de associação (r = 0,99). As quantidades de fósforo extraído do solo pelas soluções tiveram alto grau de relação com as quantidades de fósforo absorvido e com o acúmulo de matéria seca pelas plantas de milho; as soluções não diferiram na relação com as quantidades de fósforo extraído do solo e o fósforo absorvido pelas plantas de milho. As duas soluções testadas são eficientes para a avaliação da disponibilidade de fósforo no solo para a cultura do milho.