North central regional potassium studies I. Field studies with alfalfa

Potassium (K)2 availability varies widely in soils of the North Central Region of the United States and the adjoining areas of Canada. Soils in the western part of the region generally contain adequate amounts of plant-available K, but in other parts of the region, soils vary from those with abundant supplies of available K to those that are very deficient. Present techniques for predicting crop requirements for K fertilizer on different soils based on the determination of all or a portion of the exchangeable K in the plow layer are often inadequate, even when applied within restricted soil areas. In view of the wide range of K availability in different soils of the region, more effective methods of assessing the K status of the soils must be developed if efficient use of K fertilizers is to be accomplished. Therefore, the major objective of this study was to investigate the relationship between crop yield response from K fertilizer or uptake of soil K by plants in the field and different laboratory indexes of plant-available K

North central regional potassium studies III. Field studies with corn

Corn is sensitive to a deficiency of potassium (K),2 and yields of corn on K-deficient soils often are increased by K fertilizer applications. K deficiencies in corn have been observed or yield increases have been obtained from K fertilizer applications on many soils in the North Central Region of the United States. However, many other soils in the region have high levels of available K, and applications of K fertilizers on these soils have not increased corn yields. Therefore, it is important to have effective methods of estimating plant availability of K in different soils and to develop methods of predicting the yield response which can be expected from applications of K fertilizer for corn grown on different soils. The increases in yields of corn and other crops obtained from applications of K fertilizer have been shown in some studies to be inversely related to the level of exchangeable K in air-dry samples of the surface soil (5, 7). Therefore, this determination is commonly used in soil testing laboratories to estimate K availability. Other studies, however, have shown that the amount of exchangeable K in some soils is markedly changed by drying the soil (1, 2, 9, 17, 18). In some of these studies, the level of exchangeable K in undried soil samples provided a better estimate of K availability to plants than did the exchangeable K in dry soil samples (2,9,17). Matthews and Sherrell (18), on the other hand, studied the relation between exchangeable K in the soil and the yield of potatoes grown on sandy soils in Ontario, Canada and found a higher correlation with exchangeable K values for oven-dry soils than for undried soils

How a corn plant develops

There’s more than meets the eye in a field of growing corn. One way to look behind the scene is to consider the cornfield as a complex and constantly changing community. It is a manufacturing community, with many thousands of factories per acre. Every corn plant is a factory that produces dry matter. The corn plant is one of the most efficient factories in the world!https://lib.dr.iastate.edu/specialreports/1045/thumbnail.jp

Plant availability of added phosphorus in different Iowa soils

Laboratory and greenhouse experiments were conducted to study the availability of fertilizer P in 20 samples of different soils representing 10 of the principal soil associations in Iowa. Ryegrass plants recovered an average of approximately 50 percent of the added fertilizer P during a 385-day cropping period in the greenhouse. It appeared that continued cropping would have resulted in very little additional recovery of the added P. Differences in recovery of the added P from the different soils were relatively small, despite differences in rate of fertilizer addition or differences in soil pH, CaCO3 content, level of available soil P, soil organic matter content, and soil texture

Comparisons of laboratory and greenhouse indexes of nutrient availability in soils

Accurate indexes of the availability to plants of nutrients in soils are needed for comparisons of different chemical tests to determine which tests should be used in the laboratory for any given group of soils. This study was conducted to develop and improve techniques for obtaining such standard indexes of nutrient availability to plants. Emphasis was placed on: (a) treating the soil similarly (or uniformly) before testing in the greenhouse and laboratory and (b) avoiding treatments during the greenhouse cropping that might influence the availability of the soil nutrient being tested. The greenhouse technique involved growing plants on undried samples of 24 different soils. Water was added directly to the soils during plant growth, but nutrients other than the one being tested were added by a method which minimized contact with the soil

How a soybean plant develops

Compiled in this publication are years of research, study and observation o f exactly how a soybean plant develops. Photographs and accompanying text record the findings for each major stage of development in the soybean plant’s life.https://lib.dr.iastate.edu/specialreports/1050/thumbnail.jp

Available-sulfur status of some representative Iowa soils

Greenhouse experiments with ryegrass were conducted to evaluate and characterize plant availability of native and added sulfur in samples of Iowa soils. Fourteen surface soil (0-6 inches) and five subsoil (18-24 inches) samples from different sites in Iowa and two surface soil samples from S-deficient out-of-state sites were studied. Laboratory analyses were made to characterize the soil samples and to evaluate the results of different extractants as indexes of the S-supplying abilities of the soils. Plant uptake of S from the soil samples with no added S during a 202-day cropping period (five harvests) varied from 1 to 39 mg S/1500 g of soil (39 mg S/1500 g of soil is approximately equivalent to 50 lb S/acre six inches of soil in the field). Sulfur uptake was greatest during the first 70 days of cropping (two harvests), but continued at a slower, essentially constant daily rate throughout the rest of the cropping period. Although relatively slow for all soil samples, the rate of S uptake during this later cropping varied markedly among the different soil samples, with the rates for the surface soil samples being directly related to the amounts of S taken up by the plants in the earlier cropping period. The rates of uptake were very slow from most of the subsoil samples, and many plants on these subsoils died. Air-drying the soil samples before cropping resulted in increased plant yields and increased S uptake by the plants

P and K Fertilizers for Corn - How to Apply

More Iowa corn acres could be fertilized profitably with phosphorus and potassium. Both hill (row) and broadcast application have their place. Here\u27s what research tells us about methods of application

Exchangeable Potassium and Clay Minerals in Selected Iowa Soil Profiles

Exchangeable K values and X-ray diffraction patterns were obtained for soil samples from several modal profiles of nine different soil series in Iowa. Exchangeable K in moist subsoils was consistently low and almost always lower than in the moist surface soil. Drying increased exchangeable K in all the soils, but the increase due to drying varied between soil series and with depth in the profile of each series. Reversion of exchangeable K to a non-exchangeable form on rewetting the oven-dry samples generally increased with depth in the profile but the exchangeable K never decreased to the original moist level. X-ray diffraction analyses showed the presence of montmorillonite, chorlite, illite and/ or mica, and kaolinite in all the profiles, with mortmorillonite predominating. Vermiculite was present in some of the soil series. No relationship between the clay mineral content and the amount of exchangeable K could be established