D. A. Whitney

Phosphorus, potassium, chloride, and fungicide effects on wheat yield and leaf rust severity

Abstract Plant nutrition and disease suppression are among the most important management tools for producers of hard red winter wheat (Triticum aestivum L.) in the central and southern Great Plains. This study was conducted to examine the effects of phosphorus (P) (0, 15, and 30 kg ha−1) and potassium (K) (0, 37, and 74 kg ha−1) fertilization, foliar fungicide application, and cultivar disease tolerance on wheat yield, yield components, and severity of leaf rust (Puccinia triticina Eriks.). Compared with no P, fertilizing with P increased yield by as much as 60% (>1.3 Mg ha−1 increase). Yield of cultivars susceptible to leaf rust was nearly 0.6 Mg ha−1 less without K than with K fertilization. Fungicide application resulted in mean yields of 4.8 Mg ha−1 for both resistant and susceptible cultivars, however, yield of susceptible cultivars was suppressed more than yield of resistant ones without fungicide. Although P fertilization had a moderately suppressive effect on leaf rust, the increased yield was primarily due to production of about 50% more heads m−2 apparently from more prolific tillering. Similarly, K fertilization appeared to reduce leaf rust severity and improve yield by increasing kernel weight, but this response may have been related partially to chloride (Cl) in the KCl fertilizer. Correlations suggested that improving dry matter production and N, P, and K uptakes at the boot stage by P and K fertilization can reduce leaf rust severity later in the growing season and increase wheat grain yield. These results indicate that especially P fertilization, but also K fertilization and fungicide application, are important management tools for reducing disease and increasing winter wheat yield.

Effects of 30 years of cropping and tillage systems on surface soil test changes

Abstract A common belief is that no‐till systems with adequate fertility will improve soil quality over other tillage systems. The objectives of this study were to determine if crop phase, tillage systems, and n rate in a long‐term rotation affected soil chemical analyses in the surface 15 cm of soil and to evaluate the trend in chemical analyses. To test this hypothesis, surface soil samples were taken from a long‐term (30‐year) cropping and tillage study. This study was initiated in 1965 on a Harney silt loam soil in Central Kansas with every phase of the wheat‐sorghum‐fallow (WDF) rotation included each year. Tillage systems included clear‐till (CT), reduced‐till (RT), and no‐till (NT). In 1975, four nitrogen (N) rates (0, 22, 45, 67 kg N ha1) were incorporated by subdividing the tillage plots. Topdressed N, as ammonium nitrate, was the only fertilizer added throughout the duration of the study. Soil samples were taken at depths of 0 to 7.5 and 7.5 to 15 cm in all plots in 1965 and in 1995. In 1998, soils on 1997 sorghum plots were samples in 2.5‐cm increments to 15 cm. Samples from all dates were analyzed for pH, available phosphorus (AP), and organic matter (OM), and deviations from the controls from 1965 to 1995 were assessed by subtracting 1995 results from 1965 results. The change in soil pH showed a crop phase by sample depth interaction. In the wheat phase, pH in the top 7.5 cm increased by 0.19 and increased by 0.28 in the 7.5–15 cm layer. In the fallow phase, pH increased by 0.04 and 0.35 in the top 7.5 cm and 7.5–15 cm layers, respectively. The pH change for sorghum was intermediate for both depths. The increase in overall pH from 1965 to 1995 was unexpected and contrary to normal expectations of a decrease over time. Soil OM was not changed significantly over the 30 years of the study, suggesting that OM buildup or depletion is very slow under this cropping system on a nearly level soil with minimal soil erosion. Increasing the rate of N application significantly reduced pH in the upper increment samples, but had little effect on pH below 10 cm. The NT system had the lowest surface increment in pH, but differences among tillage systems were minimal below 7.6 cm. The AP was highest for NT in the surface increment, but for CT at deeper depths. Likewise, OM was highest for NT in the 2.5 cm increment and the CT at deeper increments. Under the present N management, pH may reach levels where herbicide effectiveness and phosphorus availability could be affected adversely. Deep tillage by one‐way or mold‐board plowing might be an interim solution to raise the pH before liming is implemented or P fertilizer is added to maintain adequate AP throughout the top 15 cm. Nitrogen management may need to be changed to some form of band‐type placement to reduce the total N applied. Under the conditions of this study (WSF, reduced tillage, and 57 cm annual precipitation), soil OM increased very slowly.

Effect of microwave radiation drying on soil chemical and mineralogical analysis 1

Abstract Soils dried by microwave radiation drying had chemical test values different from those of either air‐ or oven‐dried soils. The effects, however, were not consistent among the four soils tested, indicating that neither clay content nor organic matter governed the observed response. Some test values were correlated to accumulative radiation received, but not always for the same analysis or the same soil. The erratic chemical response soils exhibited to microwave drying indicate that this method should not be used in any chemical‐test procedure without first establishing a suitable correlation factor for soil type and drying time. Microwave drying did not alter the clays or any of their properties tested which suggests that this method could be used to prepare slides for X‐ray diffraction analysis in substantially less time than is required with air drying. Microwave drying reduced the tendency of clay suspensions to crack and peel from the glass slides.

Nutrient contents of washed and unwashed grain sorghum plant tissues compared

Abstract Analyses of deionized, distilled, water‐washed grain sorghum (Sorghum bicolor (L.) Moench) plant‐tissue parts throughout the plants growth cycle for Zn, Cu, Fe, Mn, Mg, and Ca contents showed no significant change, except for Fe, in nutrient concentrations from those of unwashed tissue. Iron concentrations were considerably higher in unwashed blade, sheath, and head tissue than in washed parts. Differences between unwashed and washed tissues varied throughout the plants growth cycle. Iron concentrations in the culm were affected only slightly by washing. Zinc, Cu, and Mn concentrations in plant tissue were affected least by washing. Average Zn concentrations of washed tissue were higher in all plant parts, but not consistently higher from one sampling date to the next. Average Mg and Ca concentrations were slightly higher in unwashed than washed blade and sheath tissue, primarily because concentrations in unwashed tissue tended to be higher late in the growth cycle.

Meta-analysis of Winter Wheat Response to Chloride Fertilization in Kansas

Cereal grain yield response to chloride (Cl) fertilization has been reported in most of the Great Plains. The objective of this study was to use meta-analytic methods to summarize and provide quantitative estimates of the effects of soil and fertilizer Cl on wheat (Triticum aestivum L.) response including grain yield and flag leaf Cl tissue level. Meta-analysis evaluated the effect of soil and fertilizer Cl application from different studies on a common scale of effect size. Chloride tissue concentration using the flag leaf correlated well with fertilizer plus soil Cl at a depth of 0–60 cm. However, our analysis indicates possible luxury uptake of Cl in relation to grain yield, with a possible upper limit in plant uptake with soil Cl levels around 68 kg Cl ha–1. Application of Cl fertilizer generated average wheat yield increases of approximately 8%.

NITROGEN, PHOSPHORUS, AND POTASSIUM EFFECTS ON GRAIN SORGHUM PRODUCTION AND STALK ROT FOLLOWING ALFALFA AND BIRDSFOOT TREFOIL

Grain sorghum [Sorghum bicolor (L.)], grown on the often infertile claypan soils of the eastern Great Plains, requires attention to soil fertility. Experimental objectives were to determine the effects of phosphorus (P) and potassium (K) fertility levels, N application, and legume residual on grain sorghum production and stalk rot. Following alfalfa and birdsfoot trefoil, first-year sorghum yield was 7 Mg ha−1 and not affected by N fertilizer. In subsequent years, yield increases due to N were less than 20%. Sorghum yield increased at low P and K rates, especially with nitrogen (N) fertilization and was greater following birdsfoot trefoil than following alfalfa. In 1995 when fertilized with N, lodging and stalk rot severity were increased by P and reduced by K. In 1996, stalk rot severity was reduced by K fertilization. Grain sorghum, grown after legume crops, required minimal levels of P and K, especially when N fertilizer was added.

Responsiveness of Kansas soil series to sulfur application under greenhouse conditions

Abstract Soil series of extensive acreage were selected to evaluate their S‐supplying power under greenhouse conditions using alfalfa in one study and corn and grain sorghum as test crops in a second study. The soils were divided into two major groups by textural classification for statistical evaluations. The addition of sulfur significantly increased dry matter yields and sulfur content of the plant material on all soils through the course of these studies. Significant predictors of sulfur uptake include extractable SO4‐S and organic matter. Organic matter was a significant predictor of the percent yield response above the check yields on soils receiving S applications using corn and grain sorghum as test crops. Based on this equation, yield response would be expected in this greenhouse study with an organic matter content of 2.6% or less.

Effects of phosphorus application method and rate on furrow‐irrigated ridge‐tilled grain sorghum

Abstract Conservation tillage systems, including ridge‐tillage, have become increasing popular with producers in the central Great Plains because of their effectiveness in controlling soil erosion and conserving water. A major disadvantage of the ridge system is that nutrient placement options are limited by lack of any primary tillage options. The objective of this research was to investigate the effects of method of phosphorus (P) placement and rate on irrigated grain sorghum [Sorghum bicolor (L.) Moench] grown in a ridge‐tillage system on a soil low in available P. This experiment was conducted from 1993 to 1995 on a producers field near the North Central Kansas Experiment Field at Scandia, Kansas on a Carr sandy loam soil (course, loamy, mixed, calcareous, mesic, Typic Udifuvents). Treatments consisted of fertilizer application methods, surface broadcast, single band starter (5 cm to the side and 5 cm below seed), dual band starter (one band on each side of the row), and knifed in the center of the row middle (38 cm from each adjacent row). Each of these treatments was made at either 22 or 44 kg P2O5 ha‐1, and nitrogen (N) also was included at the rate of 13 kg ha‐1. Additional treatments were, a combination of 13 kg N and 44 kg P2O5 ha‐1 applied half broadcast and half as a single band starter, a 1:1 N:P2O5 ratio (44 kg N and 44 kg P2O5 ha‐1) applied as a single band starter, and a 3:1 ratio (134 kg N and 44 kg P2O5 ha‐1) applied as a single band starter. A no‐P check plot also was included. Broadcast and center‐of‐row middle knife applications were made approximately 1 week before planting. After planting, N was balanced on all plots to give a total of 180 kg ha‐1. Applied P treatments improved grain yield and nutrient uptake and consistently shortened the time from emergence to mid‐bloom in all 3 years of the experiment. On this low soil test P soil, treatments that subsurface banded P increased grain yield by 1.27 Mg ha‐1 compared to broadcast treatments. Placing N and P in a single starter band 5 cm to the side and 5 cm below the seed was as effective as placing a band on each side of the row. Knife applying N and P in the center of the row was not as effective as placement beside the row. Single band starter application of N and P in a 1:1 and or 3:1 N:P2O5 ratio consistently increased yields and nutrient uptake and shortened the time to mid‐bloom as compared to the single band starter treatment that provided only 13 kg N ha‐1. Over the 3 years of the study, these 1:1 and 3:1 N:P2O5 ratio starters were clearly superior to an other treatments.

Response to lime and P by several genetic sources of corn (Zsa mays L.) on a low pH and P soil in the greenhouse 1

Abstract The objective of this study was to investigate the response of 16 different genetic sources of corn (Zea mays L.) to lime and P application on a low pH and P Parsons silt loam soil in the greenhouse. A highly significant lime x P interaction was found for both dry matter production and P concentration. Phosphorus increased both dry matter production and P content of plant tissues with or without lime application. However, liming produced a detrimental effect when P was applied but no effect when no P was applied. Corn genetic sources showed a highly significant interaction with P treatment, but not with lime for both dry matter production and P concentration. The results suggest that improvement in corn growth could be achieved in a low P soil environment by genetic selection.

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.