Effect of fertilization and irrigation upon NPK composition of corn leaves,on corn yields,and available k in soil

Abstract

Corn (Zea mays L.) was grown for three consecutive years on Congaree loam to measure the effects of rates of N, P, and K fertilization and irrigation on the nutrient concentration of leaves, the level of available K in the soil, and on the yield of corn. Plant nutrients consisting of 0, 56, 140, 224, and 280 kg N/ha; 0, 15, 37.5, 60, and 75 kg P/ha, and 0, 28, 70, 112, and 140 kg K/ha were applied in a central composite rotatable design in each of the three years. All plant residue was removed each year when the corn was harvested, and the plots remained fallow during the winter months. One half of the experiment was irrigated when there was a 50% depletion of available soil moisture in the 0‐ to 46‐cm soil depth.

Leaf composition was affected by fertilization and irrigation. A rapid decrease in available soil K in the 0‐ to 15‐cm depth was evident the first year with all rates of added K. The decline in available soil K was unaffected by irrigation and levels of applied N and P.

There were consistent yield responses each year to added N, no response to added P, and a response to added K only during the second year.     

Effects of nitrogen carriers,nitrogen rates,and maturity on composition of smooth bromegrass

Abstract

Magnesium and Ca concentrations in smooth bromegrass (Bromus inermis L) were not affected by late‐winter applications of N. Magnesium concentrations were constant until rapid growth in mid‐May then they declined until early June harvest. Highest seasonal concentrations were found in the fall regrowth. Calcium concentrations declined as plants matured in spring. Highest seasonal Ca concentrations were found in the fall regrowth. Nitrogen, P, and K concentrations and K/(Ca+Mg) ratios were increased by N applications during early spring but did not differ significantly by early June harvest. Nitrogen and P concentrations decreased as plants matured in spring and fall. K concentrations and K/(Ca+Mg) ratios changed inconsistently from sampling date to sampling date. Forage yields were approximately doubled by 67 kg N/ha and tripled by 202 kg N/ha. Significant yield differences were related to different N carriers.     

Effects of liming on yield,forage cation composition,and tetany potential of wheat in Kansas

Abstract

We studied the effects of liming on dry matter production, nutrient composition, and grain yields of wheat in field experiments conducted on two soil types at three locations during the 1976–77 and 1977–78 growing seasons. Lime sources were commercial agricultural lime, finely divided stack dust, and dolomitic limestone (which contained 10.6% Mg). Lime applied at 2,800 kg/ha in the 1976–77 and 10,750 kg/ha in the 1977–78 experiments provided Mg from the dolomite at rates of 300 and 1,140 kg/ha, respectively.

Soil pH was significantly increased by liming, but Mg saturation percentages were significantly greater only at the 1,140 kg/ha rate. Forage dry matter and grain yields were not increased by lime applied at the lower rate, but significant increases were found in dry‐matter production in the late fall and spring samplings of the 1977–78 experiment. Those increases in plant growth and dry matter production were probably due to reductions in the soluble Mn and Al concentrations in the soil. Forage N and P concentrations were generally not influenced by liming. Potassium concentrations in forage from the limed plots were usually equal to or greater than those in forage from unlimed plots. Calcitic limestone sources generally increased forage Ca concentrations, but liming with dolomite more often than not depressed Ca concentrations below levels found in the check plots. Dolomite, when applied at the 1,140 kg/ha rate, effectively increased the forage Mg concentration, although the concentration exceeded 0.2% only during the early growth stages. Liming generally showed no significant reduction in the tetany potential of the wheat forage as predicted by the equivalent ratio K/(Ca + Mg).     

Potato response to varying levels of soil test P and K

Abstract

Irrigated potatoes were grown on a sandy soil which ranged in available P and K from 53 to 308 and 45 to 319 kg/ha, respectively. The levels of soil P and K as measured by soil test (Bray #1) were compared with yield, specific gravity of the tubers, and P and K tissue concentrations. The response of the potato crop was correlated to soil K but not to soil P. Yields increased with increasing soil K from 45 to 196 kg/ha in the surface sample and leveled off there after. The fact that the levels of subsoil K increased with increasing surface soil K may have had somewhat of an effect on the leveling off of potato yields at 196 kg/ha of K. The lack of a yield response to soil P was associated with adequate available soil P at the lowest soil test levels.     

Soybean pod wall P and K as related to extractable P and K and grain yield

Abstract

It was proposed that the pod wall surrounding the developing soybean seed (growth stage R6) could serve as a diagnostic indicator of crop nutritional status. This was evaluated by summarizing soybean responses (R1 trifoliate and R6 pod wall P and K concentrations, and yield) to various levels of soil P and K availability in ten field experiments. Pod wall P and K concentrations were closely related to available soil P (Bray P₁) and K (MNH₄C₂H₃O₂‐pH 7.0), respectively. The relationship of pod wall P concentration to grain yield was superior to those found when either trifoliate leaf P or available soil P was related to grain yield. Pod wall K was similarly superior to leaf K or available soil K. Though further work is needed to describe changes in pod wall composition during grain‐fill, it appears that pod wall sampling offers an alternative or additional sampling interval in the evaluation of soybean nutrition     

Effets des engrais N,P et K sur le rendement et la qualite de l'ensilage ue mais

Abstract

Thirteen fertility trials were made throughout Quebec's corn growing region during 1972–74. These included eleven fertilizer combinations with corn silage as the test crop and were carried out on nine soils. Total dry matter and digestible nutrients (TDN) varied greatly from year to year, though, mean yields increased by 23 and 30 percent respectively with the 50 kg N/ha treatment, compared to control receiving no nitrogen fertilization. However, 150 kg N/ha was required to attain a maximum yield of 1250 kg/ha crude protein. Despite a 0.2 percent nitrate content found in the silage grown on the most northerly site, a 120 kg P/ha combined with 100 kg N and K gave the highest mean TDN production (9580 kg/ha).

Potassium fertilization affected plant K content of corn grown at the most northerly site only, where a 0.5 percent was found with the control on a suit containing low potassium levels. Further, striking increases in Ca and Mg concentrations were observed with corn grown on that soil. However, magnesium concentration ranging from 0.11 to 0.14 percent were found with nine field trials out of twelve. Also, low K:(Ca + Mg) ratios were found on three trials, which were increased with potassium fertilization levels of 150 kg K/ha. Accordingly, it is suggested that uptakes of 200, 48, 200, 30 and 30 kg/ha of N, P, K, Ca and Mg are required for good corn silage crops.     

Site specific soil‐test interpretation for snapbean

Abstract

Phosphorus (P) and potassium (K) requirements of snap bean (Phaseolus vulgaris L.) in North Florida are not well defined in the literature. Response of a bush type snap bean to P and K was determined in a 2‐year test at NFREC, Quincy. The resulting data were used in site specific soil‐test interpretations. Residual soil‐P levels were 7, 11, 29, and 66 mg/kg the first yr and 7, 12, 21, and 42 mg/kg the second yr, no fertilizer K was added either yr. Residual soil‐K was 26, 60, and 73 mg/kg the first yr. Fertilizer K was added the second yr at 0,95, and 190 kg/ha. Soil samples were collected from each plot near the beginning of each growing season for determination of soil‐test P and K levels. Soil type was Norfolk loamy fine sand (fine loamy, siliceous, thermic, Typic Kandiudult). Maximum nutrient levels required for snap bean were: soil‐test P 30 mg/kg and soil‐test K 80 mg/kg. Soil‐test interpretations for P were: low <15 mg/kg, medium 15 to 30 mg/kg, and high >30 mg/kg. Potassium soil‐test interpretations were low <40 mg/kg, medium 40 to 80 mg/kg, and high >80 mg/kg.     

Yield response of soybeans to P and K fertilization as correlated with soil extractable and tissue nutritional levels

Abstract

Bragg soybeans [Glycine max. (L. ) Merill] were grown under field conditions near Sanford, Florida on a tile‐drained Immokalee fine sand (sandy, siliceous, hyperthermic Arenic Haplaquod). The objectives were: 1) to assess the K and P fertilizer requirements of soybeans grown in central Florida 2) to correlate soil and tissue nutritional levels with extractable soil nutrients and 3) to assess the influence of K application time on yield.

Experimental treatments were four K rates (0, 50, 100, and 200 kg K/ha), three P rates (0, 25, and 50 kg P/ha), and two sidedress K rates (0 and 50 kg K/ha) at early bloom. Treatments were arranged in a randomized complete block design and replicated four times.

Yield increased with each increase in applied K. Statistical maximum yield was obtained on plots which contained 103 ppm double‐acid extractable K during the pod‐filling stage of growth. Tissue K at early bloom exceeded 2.85% at maximum statistical yield. Potassium applied broadcast at early bloom did not significantly influence yield.

This soil contained approximately 390 ppm double‐acid extractable P prior to P application. No significant yield response to applied P was observed, indicating that the original extractable P content of the soil was adequate for the yield level obtained.

The quadratic regression of the ratio equivalents of double‐acid extractable K:Ca + Mg on the same ratio for the plant tissue is highly significant. This expression was a good predictor of tissue accumulation of these nutrients in that the coefficient for determination was 0.68.     

Effect of N,P and K fertilizers on their availability in soil in relation to the Stevia plant (Stevia rebaudiana Bert.)

Abstract

A greenhouse experiment was conducted at the Indian Institute of Horticultural Research (IIHR), Bangalore, to study the effect of combined applications of nitrogen (N), phosphorous (P) and potassium (K) fertilizers on their availability in soils in relation to their contents in the Stevia plant. The results show that the amount of available N, P and K in soil has been found to be increased initially up to 45 days and thereafter, the amount of the same content decreased with the progress of plant growth up to 60 days irrespective of treatments. However, the magnitudes of such increases in N, P and K contents both in soils and plants have also been enhanced with the simultaneous application of N, P and K (40:20:30) kg/ha over that of their corresponding individual applications.     

Effect on N P K applications on potatoes grown on a well decomposed and intensively fertilized organic soil

Abstract

Using predictably excessive rates of N, P and K for potatoes on a well decomposed and intensively fertilized organic soil, it was observed that while N depressed yields somewhat, there were neither deleterious nor beneficial effects from the application of P or K. The highest rates of P and K used were 1792 and 3584 kg/ha respectively. Increasing rates of N decreased B concentrations in the potato leaf tissue while increasing rate of K resulted in increasing concentrations of B. Zinc tended to be higher in leaf tissue as excessive phosphorus application rates increased.     

Yield of alfalfa as influenced by levels of P and K fertilization

Abstract

This study was conducted to ascertain further the need for P and K fertilizers to obtain maximum herbage yields from alfalfa (Medicago sativa L.). Vernal alfalfa was established on a low K Piano silt loam (Typic Argiudoll) soil and topdressed with zero, 22.4, and 44.8 kg/ha of P in autumn of seeding year and with zero, 224, and 672 kg/ha of K as KC1 each autumn. The harvest schedule was three cuts annually at first flower; a schedule widely recommended in the North Lake states. No statistical significance was found for P levels nor for the P x K interaction; significance was found only for K levels. Maximum herbage yield was obtained with 224 kg/ha of K in the first harvest year, but with the 672 kg/ha of K rate in the second harvest year. Herbage K and Cl percentages and amounts removed from the soil increased significantly each year with each increase in K applied. Herbage P and N percentages were decreased significantly with the first increment of K. Residual herbage yields showed dramatically the influence of K fertilization on winter survival. All alfalfa stands with no K fertilization were killed completely. Residual yields and stands increased with each increase in K applied. Yield increase over the control was significant only with the second increment of K, while stands increased significantly with each increase in K applied. These data continue to confirm that high levels of soil K are needed for stand survival as well as for high herbage yields.     

Phosphorus sorption by four soils receiving long‐term applications of fertilizer

Abstract

A laboratory study was conducted to evaluate P sorption in the Ap horizon of four soil series in the Ultisol order (Benndale Is, Hartsells fsl, Lucedale fsl, and Dewey sicl) receiving the same fertility treatments since 1929. Soil was collected in the spring of 1985 from 4 treatments: i) no‐lime, plus P (total fertilizer P = 1584 kg/ha from 1929 to 1985); ii) no‐K, plus P (total fertilizer P = 1584 kg/ha); iii) low‐P (total fertilizer P = 442 kg/ha); 4) standard treatment (total fertilizer P = 2376 kg/ha). The soils and treatments within a soil varied in pH, total P, Mehlich 1 extractable P, K, Ca and Mg, and KC1 extractable Al. The four soils had large differences in P sorption capacity which increased with increasing clay content. The Dewey (27 % clay) soil had the highest P sorption capacity and the Benndale (4 % clay) soil had the smallest P sorption capacity. Sorption of P within a soil was affected by the rate of added P and past fertility treatment. Treatment differences in P sorption were due primarily to the level of extractable P and soil pH. Within a given soil, P sorption (at a given rate of added P) generally decreased as the level of extractable P increased. Regression analysis of P sorption data for equilibrium P concentrations of 1 to 32 μmol/L showed that the parti‐ tioning between sorbed and solution P (buffer power) had not been changed by 56 years of annual applications of P. The maximum P sorption capacity of the four soils was decreased slightly by P fertilization.     

Soil phosphorus after 25 years of cropping with five rates of phosphorus application

Abstract

Rate of change of levels of various soil P forms as affected by P fertilizer application and crop removal is important for determining long term P fertilization policy. A rotation‐fertility experiment conducted for 25 years at the Purdue Agronomy Farm, West Lafayette, IN has provided data for calculating changes in soil P levels. Average annual P applications ranged from 0 to 54 kg/ha. Soil samples taken initially and after 25 years were analyzed for resin exchangeable P, Bray Pl, and total P. A linear relation between P applied minus P removed by cropping and Bray Pl indicated that Bray Pl increased one μg/g for every 17 kg net P/ha added. When P application on some plots was stopped for up to eight years, resin and Bray Pl levels decreased. The rate of decrease was greater the higher the P level at the time P application ceased. Increase in soil P level by fertilizer addition and decrease in P level by cropping appeared to be reversible processes.     

Influence of high rates of topdressed KCl and K2SO4 on recovery of K,Cl, and SO4‐S by alfalfa and residual amount remaining in the soil

Abstract

This study was conducted to ascertain the percent of available K, Cl, and SO₄‐S recovered by alfalfa (Medicago sativa L. cv. ‘Vernal') herbage when various rates of K as KCl and K₂SO₄ were topdressed and also to determine where residual K, Cl, and SO₄‐S accumulated in the soil profile. An established stand of alfalfa growing on low fertility silt loam soil was topdressed in the spring of each of two harvest years with 0, 448, 896, 1344, and 1792 kg/ha of K as KCl or K₂SO₄. Four harvests were taken during each harvest year (1972 and 1973). Soil samples were taken during the autumn of 1973 to a depth of 91.4 cm in KCl‐fertilized plots, and to a depth of 76.2 cm in K₂SO₄‐fertilized and control plots.

Potassium recovery by alfalfa during two harvest years where K as KCl was applied at 448, 896, 1344, and 1792 kg/ha/yr was 56, 33, 20, and 17%, respectively. Recovery of available Cl from those same treatments was 30, 17, 12, and 10%, respectively. Where K as K₂SO₄ was applied at 448, 896, 1344, and 1792 kg/ha/yr, 55, 35, 27, and 22%, respectively, of available K was recovered. Recovery of available SO₄‐S from those same treatments was 16, 9, 7, and 5%, respectively. At the end of two years, a majority of the residual K was in the top 15.2 cm of soil. Residual Cl and SO₄‐S were concentrated at a depth of 30.5 to 76.2 cm in the soil profile.     

Foliar nutrient status in three boreal species for three years following hexazinone application

Abstract

Effects of hexazinone on the dynamics of macronutrients were studied in the foliage of trembling aspen, showy aster and marsh reed grass for three years after broadcast application of 10% granular formulation of hexazinone at 0, 2, and 4 kg ai/ha rates in August 1986 in a 3‐year‐old mixedwood cutover in a boreal forest. In untreated plots, nutrient concentrations followed normal patterns: calcium (Ca) increased from spring to late summer; potassium (K), phosphorus (P), sulfur (S), and nitrogen (N) peaked in early summer and declined towards fall; and magnesium (Mg) did not show any definite trends. At each sampling date, the coefficient of variation ranged from <10% for Ca, Mg, K and total N to 10–20% for P and S. Seasonal variations in the concentrations of each element were greater than the year‐to‐year variations. In treated plots, hexazinone application resulted in elevated concentrations of total Ca, Mg, K, P, S, and N during the first growing season, but these changes were only significant (P<0.05) at the 4 kg rate. The intensity of the effects declined by the end of the second growing season following herbicide application. In 1989, differences between nutrient levels in foliage from control and treated sites were significant (P<0.05) only for total N. Consequently, any changes in the nutrient status of hexazinone‐treated sites (beyond two years post‐treatment) are not expected to result from changes in foliar nutrient levels, but rather from changes in litter fall quantities, species dominance and total vegetation cover. Nutrient quality of forage for wildlife would not be affected beyond two years post‐treatment.     

Effects of fertilization and irrigation on corn yields,p content of corn leaves,and available p in soil

Abstract

Experiments were conducted on Congaree loam at Orange, Virginia, in 1963, 1964, and 1965 to measure the response of corn to irrigation and to 3 levels of P. Rate of N was 140 kg/ha. Levels of P were 0, 37.5, and 75 kg/ha; while the rate of K. was 70 kg/ha. All micronutrients were applied in recommended amounts. Excellent corn silage and grain yields were obtained and there was no response to added V except for grain yields on irrigated plots. Cropping with corn, irrigation, and fertilization appeared to have little effect on the P content of the 0‐ to 15‐cm soil layer. Irrigation and P fertilization did not affect the P content of the corn leaves. Fractionation of P indicated appreciable amounts of A1‐P, Fe‐P, and Ca‐P to a depth of 140 cm with less Al‐P than the other forms.

Moisture extraction by the corn, as measured with Bouyoucos blocks, indicated that the corn was utilizing moisture to a depth of 120 cm during silking and tasseling. The corn roots, therefore, had access to appreciable amounts of P below the 0‐ to 15‐cm soil depth. Since there was essentially no change in the P content of the 0‐ to 15‐cm soil depth, the corn apparently was either utilizing most of its P from soil depths below 15 cm, or available P was being maintained at a fairly constant amount from the various forms in which it was found in the soil. This is in contrast to the usual situation in which plants utilize appreciable amounts of P from, the 0‐ to 15‐cm soil depth.     

县级测土配方施肥指标体系建立研究—以江苏省江都市水稻为例

以江苏省江都市水稻为例,基于地力差减法预测氮肥用量、 养分丰缺指标法预测磷钾肥用量,构建县域测土配方施肥指标体系,研究分析20052011年测土配方施肥田间试验示范。结果表明,当种植水稻预测目标产量为6825~9270 kg/hm2（平均为8145 kg/hm2）,氮肥推荐用量为146.42~57.4 kg/hm2（平均为207.5~ kg/hm2）。磷钾肥施用标准: 当有效磷含量高于21 mg/kg,不推荐施用磷肥;当有效磷含量在17~21 mg/kg时,推荐施磷（P2O5）量为40.5 kg/hm2;当有效磷含量在10~17 mg/kg时,推荐施磷（P2O5）量为 48 kg/hm2;当有效磷含量低于10 mg/kg 时,推荐施磷（P2O5）量为64.5 kg/hm2。当速效钾含量高于140 mg/kg,不推荐施用钾肥;当速效钾含量在115~140 mg/kg时,推荐施钾（K2O）量为 22.5 kg/hm2;当速效钾含量在60~115 mg/kg时,推荐施钾（K2O）量为40.5 kg/hm2;当速效钾含量低于60 mg/kg 时,推荐施钾（K2O）量为 82.5 kg/hm2。同时对施肥指标体系建立进行校验分析,结果表明基于试验建立施肥指标体系是可行的,从而为构建县域测土配方施肥指标体系提供了方法,达到因土施肥的目的。     

Influence of lime and phosphorus on soybean (Glycine max (L.) Merrill) yield,leaf and seed composition on a paleudult soil

Abstract

This research was undertaken on a paleudult soil in southern Brazil, 30° south latitude, to quantify lime and P effect upon soybean (Glycine max (L.) Merrill). A lime x P factorial experience with lime treatments of 0, 0.5, 1, and 2 times SMP interpretation to pH 6.5, and 0, 44, 88, 132, and 176 kg P/ha with 3 replications were installed. The experiment was conducted for 2 years (1973–74, 1974–75), with leaf‐N, P, and K; yield; seed‐N, P, and K; Bray P₂ (0.03N NH₄F + 0.1N HC1) avail‐able‐P and soil pH measurements completed each year. Data was evaluated with linear, quadratic, logarithmic, polynomial, segmented line, and multiple regression using the coefficient of determination as goodness of fit.

The best model fit between P treatment and Bray P₂ available‐P was a quadratic equation; the model between relative yield and Bray P_2‐P with 54% of the relative yield attributed to Bray P₂ available‐P, a sigmented line. This model indicated point of maximum yield (91% relative yield) was obtained at 7.4 ppm‐P, with no increase in relative yield with increasing levels of soil available‐P. To calculate the P fertilizer necessary to increase available soil‐P to the level of maximum yield of equation Y_p = [1639(7.4 ‐ x_s)]^1/2, where Y_p = kg P/ha fertilizer needed; and x_s = initial Bray P₂ soil available‐P in ppm's. The lime effect upon soil pH was best described as a linear relationship. Yield increase with lime at this site was not significant at the 5% level.

The leaf‐N, P, and K increased significantly with soil available‐P levels. A second degree polynomial with logarithmic function best defined these relationships. The calculated DRIS indices and sum proved useful to evaluate the plant‐N, P, and K balance of each treatment.

Only seed‐P level was directly related to soil available‐P. Both seed‐N and seed‐K were highly correlated with indirect effects of soil available‐P levels.

Results from this study suggest the segmented line model would best interpret soybean yield response to Bray P₂ available‐P for this soil. To obtain maximum yield using this model rather than the second degree polynomial would require less fertilizer P. Foliar analyses interpretation confirmed adequate plant‐P level would be supplied for maximum yield at this level of fertilization.     

A case study on the estimation accuracy of soil properties and fertilizer rates for different soil‐sampling grids

Soil testing is used to help make fertilizer recommendations for greater yields and profits. But the increase of soil‐sampling density raises costs of sample collection and analyses. The aim of this study was to compare grid‐cell sampling densities (1, 2, and 4 ha) in terms of the estimation accuracy of macronutrients (P, K, Mg) availability and pH and to investigate how sampling density affects the amount of fertilizers and lime recommended and correctly applied to winter wheat (Triticum aestivum L.). The distribution of liming requirements and available nutrients were quite similar for the 1‐ and 2‐ha grids but notably different for the 4‐ha grid. However, the whole‐field average values of pH and P, K, and Mg concentrations in soil obtained for different sampling densities were very similar, thus placing, respectively, the soil of the studied area in the same class of liming needs and nutrient availability. The range and estimation errors of these parameters decreased with sampling‐grid size increase. The amount of lime and fertilizers to be applied on the field and the portion of a field correctly limed or fertilized depended on the soil chemical property considered. If one treats the 1‐ha grid as the reference and the most correct soil‐sampling approach, 2‐ha grid offered the greatest part of the field to be adequately fertilized with lime, P, and K. However, fertilization with Mg was much more appropriate if the recommendation was based on 4‐ha, than on a 2‐ha soil‐sampling grid. To gain an insight into soil variation and soil process occurring at small scale, laboratory and geostatistical analyses on individual soil samples may be necessary in some cases. Possibly, such costly research can deliver relevant information which could be then applied into farmer's practice.     

Nitrogen,Phosphorus, and Potassium Fertilization of a Coastal Plain Cotton–Peanut Rotation

Abstract

A cotton (Gossypium hirsutum)–peanut (Arachis hypogaea L.) rotation is widely practiced in the southern coastal plain following the reemergence of cotton as a major crop in the 1990s. Very few plant nutrition studies have been conducted in the coastal plain (CP) with modern cotton varieties and none with the cotton–peanut rotation. Experiments with varying rates of nitrogen (N), phosphorus (P), and potassium (K) were conducted to determine if the recommendations from soil tests provide adequate nutrition for maximizing profit when yield goals are Georgia state averages, due to other conditions. From 1996 through 1998, N, P, and K experiments were conducted in cotton crops, and P and K experiments were conducted in peanut crops on Tifton loamy sand. Initial Mehlich‐1 P was 2 to 3 mg/kg (“low”) and Mehlich‐1 K was 50 to 64 mg/kg (“medium” for cotton and “high” for peanut). Each crop was grown each year. State average yields of cotton and peanuts were produced. There was no response in cotton yield to N rates from 34 to 136 kg N/ha. Lack of response may have been due to the fact that the field had not been in production for several years prior to 1996 and there was ample soil mineral N. In 1997 and 1998, residual N provided by N fixation by the previous peanut crop appeared to be sufficient. Maximum profit from P fertilization in cotton was attained at 50 kg P/ha, the recommendation from the soil test. However, a University of Georgia Cooperative Extension Service recommendation to double the P rate for new land with a “low” Mehlich‐1 P soil test was not validated. Cotton yield did not respond to K fertilization even though an application of 55 kg K/ha/year was recommended from the soil test. Peanut yield and grade did not respond to either P or K fertilization. The recommendation from the soil test was 40 kg P/ha/year and no K. Estimates of P removal were 11 kg/ha for cotton and 8 mg/ha for peanut crops. Estimates of K removal were 25 kg/ha for cotton and 22 kg/ha for peanut crops. Over 3 years, soil P was not depleted, but soil K was depleted. Approximately 12 kg P/ha were required to raise soil test P 1 mg/kg and 18 kg K/ha were required to raise soil test K 1 mg/kg (49 lb. P₂O₅ to increase the P test 1 lb./acre, 38 lb. K₂O to raise the K test 1 lb./acre). Additional studies are needed, but the current studies suggest that revisions in recommendations are needed for both cotton and peanut crops.