Role of magnesium in plants

Magnesium is one of 13 mineral elements required by plants and one of at least 17 required by animals. The element was first isolated in chemically pure state by Sir Humphry Davy during the years 1807 to 1812 and its necessity for plant growth was shown by J. von Sachs and W. Knop in the 1860's. Its presence in the chlorophyll molecule was detected by R. Willstitter in 1913. More details on the history of Mg research appear in earlier reviews (1, 8, 11 and 20)

Air-Flow Planimeter for Measuring Detached Leaf Area

An apparatus has been designed and tested for measuring area of detached leaves of all shapes. The apparatus is easy to operate and gives accurate results rapidly. Measurement variability is generally less than 1%

Fertilization of Pasture and Range in the United States

The importance of the forage resource in the United States is apparent from the 225-million ha of humid-region pasture, and 122-million ha of arid rangeland in the Great Plains and Western States. The objective of this report is to briefly summarize the effect of fertilizer on yield and forage quality of pasture and range, particularly their effect on beef production. In the past 25 years, beef cow herds have replaced both dairy cows and sheep on many forage-producing areas. The limited forage and range resources in the semiarid and arid Western States may restrict further expansion of cow-calf operations, except in areas where irrigated pasture can be developed or where forage productivity can be increased by fertilization. Water is less limiting in the Eastern States, assuring more reliable supplies and potentially greater amounts of forage to support the beef industry. Thus, cow-calf numbers in some South-Atlantic and North-Central States have greatly increased. Most of the cow-calf operation in the southern region and in the Midwest resemble ranch operations of old, in which inputs and costs are kept as low as possible. Implementing improved practices (i.e., improved forage varieties, fertilization, grazing management) would greatly increase beef production in these areas

Selenium in Soils and Plants

Prior to 1960, selenium was important because of its uptake by selenium-accumulator plants and its subsequent toxicity to animals eating these plants. The first reports on the nutritional importance of selenium were published in 1958, and attention was then drawn to another aspect of selenium.¹ The growing incidence of nutritional muscular dystrophy in animals on improved postures was soon identified as a selenium-responsive disorder (Figure 1). Since then, a large amount of literature has accumulated on various aspects of selenium in the soil-plant animal system. Reviews include those by Allaway et al.,² Klayman and Gunther,³ the NRC,¹,? and Oldfield.? This article reviews the role of soil and plants in selenium cycling to the animal and the return of selenium to the soil

Absorption of Excess Selenium and Sulfur by Plants and Animals

High concentrations of selenium (Se) and sulfur (S) often occur in overburden soils and underlying shales associated with western coal mining areas. Knowing the role of Se and S in the soil-plant-animal system is important for proper management of mine spoil reclamation. I will discuss recent findings about Se and S forms in soil, their absorption and accumulation by plants, and their subsequent toxicity to grazing animals. Selenium absorbed by the accumulating plants is metabolized to non-protein forms, while that absorbed by the non-accumulating plants occurs predominantly as selenomethionine which is readily absorbed by animals. In animals, both acute and chronic forms of selenosis are known. Death occurs when a large dose of highly-available Se is ingested. One chronic form "alkali disease", produces symptoms of inappetence, hair loss, hardening and extension of nails and hooves, reduced weight gains, and poor reproductive performance. Rosenfeld and Beath identified "blind staggers" as another form of selenosis, but this disorder; more appropriately called polioencephalomalacia (PEM), occurs only in ruminants. However, the attribution of "blind staggers" (PEM) to excess Se is being questioned. Recent experimental evidence has shown that PEM is likely caused by excess sulfur. Cases of this disorder have been documented in the U.S. and Canada when ruminants have high sulfate intake from herbage and drinking water. Decisions regarding western mine reclamation should consider the potential for not only causing excess Se, but also excess sulfate in water, soil, and plants

Rangeland Fertilization for Balanced Forage and Cattle Nutrition

An important grazing resource in the United States is the big sagebrush-bunchgrass complex. It occupies nearly 94 million acres in southern Idaho, Utah, western Wyoming, Nevada, southeastern Oregon and south-central Washington. This area is often referred to as the Great Basin because of its precipitation pattern. Annual precipitation is generally less than 14 inches, and most of it falls during the winter and spring. The principal grasses are perennial bunch types, including species of wheatgrass, bromegrass, bluegrass, needlegrass and fescue

Measuring and interpreting rangeland soil fertility

Fertility (FI) and a potential yield increase (PI) indexes were determined for 119 semiarid rangeland soils of south-eastern Oregon. Four hundred-gram portions of the <2 mm soil, representing 0 to 75, 75 to 150, or 150 to 300 mm depths, were placed in 400-cm³ waxed cartons, seeded with 100 'Bonneville' barley (Hordeum vulgar, L.) seeds and watered (—NS) daily to 0.3 atmosphere moisture tension. A second group was handled identically except that 50 ml of complete nutrient solution (+NS) was applied at 10-day intervals. Top growth was harvested at 40 days, dried at 100 C and the mean yield of three replications determined. The fertility index was computed as F1 = (-NS yield)/ (+NS yield) and the potential yield increase index as PI = 100 [(+NS yield) — (-NS yield)] / (—NS yield). Percentage occupancy (PO) of Agropyron desertorum was assumed to be a measure of reseeding success at the sites represented by the soils. PO was not related to FI, but was positively correlated with PI for each of the three soil depths. It is concluded from this relationship that fertilization response would be greatest on the more successfully reseeded sites

Plant nutrient content and animal health issues

The list of mineral elements necessary for livestock growth is similar to that for plants. It includes K, Ca, Mg, P, S, Cl in relatively large concentrations, as well as the trace minerals Co, Cu, Fe, Mn and Zn. Animals, but not plants, also require Na, Se, and I. Several interactions important to animal health exist. High concentrations of K will reduce Mg and Ca uptake by plants and animals increasing the risk of grass tetany in animals. Interactions of Cu, Mo, and S reduce bioavailability of Cu to animals. High concentrations of S reduce bioavailability of Se to animals

Correlation of Exposure and Potential Solar Radiation to Plant Frequency of Agropyron desertorum

The hypothesis that exposure and potential solar beam radiation are useful parameters in describing frequency response of a monoculture bunchgrass was tested. Slope, aspect [sine (azimuth angle +68°)]; and daily potential solar beam radiation (June 22) accounted for 18%, 8% and 13%, respectively, and 22% collectively, of the variation in Agropyron desertorum plant frequency. Maximum plant numbers occurred on south- to-west exposures, but these exposures had more steeply inclined slopes and actually received less potential solar radiation than others during the summer solstice. Aspect data alone are inadequate for interpreting plant response to soil moisture, temperature, and solar radiation, especially when a wide range in slope is involved

Plant Growth

Chilling temperatures in the range of 0 to 15°C greatly affect plant growth. Recent research has added to the knowledge of negative and positive effects of low temperature on growing plants