Nutrient Cycling in Soils: Sulfur

Sulfur is an essential element required for normal plant growth, a fact that has been recognized since 1860 (Alway, 1940). It is considered a secondary macronutrient, following the primary macronutrients nitrogen, phosphorus, and potassium, but is needed by plants at levels comparable to P. Sulfur deficiency will impair basic plant metabolic functions, thus reducing both crop yield and quality. Deficiencies and responses to S amendments have been reported in crops worldwide (Tisdale et al., 1986; McGrath and Zhao, 1995; Scherer, 2001), and are becoming more common (Haneklaus et al., 2008). The likelihood of a response is determined by the balance between sulfur supply and crop demand. The main reasons for recent increases in documented S deficiencies include the reduction of SO2 emissions from various industrial sources, mainly coal-fired power plants, an increase in the use of high-analysis fertilizers with little S, decreased use of S-containing pesticides, greater S removals with ever-increasing crop yields, and continued losses through leaching and erosion of topsoil. As pointed out by Haneklaus et al. (2008), in only a few years, the reputation of S has changed from that of an undesirable pollutant to a limiting factor in crop production. In this chapter, we provide current information on the demand for S in various cropping systems, what we know about the soil supply of S, the best ways of assessing S status and managing S inputs, and how all of this information can be put together to optimize crop production. In each section, references will provide the reader with an opportunity to explore the topic in greater detail than can be given in these few pages

Corn Stover Nutrient Removal Estimates for Central Iowa, USA

One of the most frequent producer-asked questions to those persons striving to secure sustainable corn (Zea mays L.) stover feedstock supplies for Iowa’s new bioenergy conversion or other bio-product facilities is “what quantity of nutrients will be removed if I harvest my stover?” Our objective is to summarize six years of field research from central Iowa, U.S.A. where more than 600, 1.5 m2 samples were collected by hand and divided into four plant fractions: vegetative material from the ear shank upward (top), vegetative material from approximately 10 cm above the soil surface to just below the ear (bottom), cobs, and grain. Another 400 stover samples, representing the vegetative material collected directly from a single-pass combine harvesting system or from stover bales were also collected and analyzed. All samples were dried, ground, and analyzed to determine C, N, P, K, Ca, Mg, S, Al, B, Cu, Fe, Mn, and Zn concentrations. Mean concentration and dry matter estimates for each sample were used to calculate nutrient removal and estimate fertilizer replacement costs which averaged $25.06,$20.04, $16.62,$19.40, and $27.41 Mg−1 for top, bottom, cob, stover, and grain fractions, respectively. We then used the plant fraction estimates to compare various stover harvest scenarios and provide an answer to the producer question posed above

Crack Deflection and Propagation in Layered Silicon Nitride/Boron Nitride Ceramics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66258/1/j.1151-2916.1998.tb02438.x.pd

Corn Stover Harvest, Tillage, and Cover Crop Effects on Soil Health Indicators

Monitoring soil health indicators (SHI) will help ensure that corn (Zea mays L.) stover harvest is sustainable. This study examines SHI changes after 5 yr of growing continuous corn with either chisel plow or no-tillage practices and harvesting 0, ∼35, or ∼60% of the stover. Two no-tillage treatments with a cereal rye (Secale cereale L.) cover crop and stover harvest rates of ∼35 or ∼60% were evaluated. All eight treatments were replicated four times in a randomized complete block design at an 11-ha site in Boone County, IA. Soil samples were collected following grain and stover harvest from 0- to 5- and 5- to 15-cm depth increments. Particulate organic matter C (POM-C) decreased when stover was removed or the soil was chisel plowed. No-till with 0% stover removal had 10 mg g–1 POM-C in the 0- to 5-cm soil layer, which was 1.9-fold higher than in other treatments. Potentially mineralizable N (PMN) was greater under cover crop treatments. Average PMN values were 56.9 and 45.5 µg g–1 PMN for no-till with cereal rye at 0- to 5- and 5- to 15-cm depths, respectively, compared with 17.5 and -3.7 µg g–1 PMN for the same no-till treatments without cereal rye. Other soil properties did not respond to increasing levels of stover removal. At this location and at the studied removal rates, 5 yr of harvesting corn stover did not decrease soil health, but POM-C data suggest that changes may be occurring. Long-term monitoring should continue to assess corn stover harvest sustainability

Effects of Grazing Management on Pasture Characteristics Affecting Sediment and Phosphorus Pollution of Pasture Streams (Progress Report)

To evaluate the effects of grazing management on pasture properties related to soil erosion and P pollution of streams, six 30-acre cool season grass pastures bisected by a stream were grazed by 15 fall-calving Angus cows by continuous stocking with full access to the stream, continuous stocking with stream access limited to a 16 x 80 foot stabilized crossing, or rotational stocking. The riparian paddocks of rotationally stocked pastures were never grazed to a sward height lower than 4 inches or longer than 4 days. Congregation areas in pastures had greater proportions of the ground that were bare or covered with manure and lower forage sward heights and masses than open areas. Stream banks had greater proportions of ground that was bare and lower forage sward height and masses than in the riparian zone from 110 to 220 feet from the bank and in the uplands. Pastures with continuous stocking and full stream access had greater proportions of bare soil and lower forage sward heights and masses on and adjacent to the stream bank compared to upland zones in the same pastures or on and adjacent to the stream bank in the ungrazed riparian buffers. This damage was particularly evident in October which would leave the banks susceptible to erosion during the winter. There was no difference in manure distribution across the different zones in pastures with full stream access. Pastures with continuous stocking and limited stream access had less bare soil, greater forage sward heights and masses on and adjacent to the banks than pastures with full stream access. There was no manure cover on or adjacent to the banks of riparian buffers in pastures with limited stream access, but manure cover was concentrated in the zone from 110 to 220 feet from the stream. The proportions of bare soil on and adjacent to stream banks in rotationally grazed pastures did not differ from ungrazed buffers and the forage sward heights and masses in these zones were intermediate between pastures with full and limited access in October. However, similar to pastures with continuous grazing and full access, manure coverage did not differ across zones of rotationally grazed pastures. The preliminary results of this project imply that limiting access to streams to stabilized crossings or use of rotational grazing may decrease the potential for sediment and phosphorus loading from stream bank erosion

Impacts of Cattle Grazing Management on Sediment and Phosphorus Loads in Surface Waters

In 2001 (year 1) and 2002 (year 2), three blocks of five 1-ac paddocks were grazed by beef cows on hills at the Iowa State University Rhodes Research and Demonstration Farm to determine the effects of grazing management on phosphorus (P) and sediment runoff from pastureland. Grazing management treatments included an ungrazed control, summer hay harvest with winter stockpiled grazing, grazing by continuous stocking to a residual sward height of 2 in., rotational stocking to a residual sward height of 2 in., and rotational stocking to a residual sward height of 4 in. At four times (late spring, mid-summer, early autumn, and early the subsequent spring) in each year, rainfall simulations were conducted at 6 sites within each paddock and 6 sites in a buffer zone down slope of each paddock. Rainfall simulators dripped at a rate of 2.8 in./hr over a 5.4- ft2 area for a period of 1.5 hours. Runoff was collected and analyzed for total sediment, total P, and total soluble P. Simultaneous to each rainfall simulation, ground cover, penetration resistance, surface roughness, slope, the contents of P and moisture of the soil, sward height and forage mass were measured. Losses of sediment, total P, and total soluble P were greater from grazed paddocks than ungrazed paddocks in year 1. However, in year 2, losses of sediment, total P, and total soluble P from paddocks grazed by rotational stocking to a sward height of 4 in. or harvested as hay during the summer and grazed during winter did not differ from ungrazed paddocks. In both years, losses of sediment, total P, and total soluble P from the buffer area immediately or 30 ft below the paddocks were lower than within the paddocks. Of the physical measurements, the proportion of ground cover was most highly related to sediment loss. Soil Bray-1 P concentrations did not differ between treatments, but were related to the losses of total and total soluble P. Results imply that sediment and phosphorus losses in pasture runoff may be reduced by managing rotational stocking to maintain adequate sward height and/or using vegetative buffer strips along pasture streams. Such management practices are particularly important in pastures on soils with high P concentrations

Stocking Rate and Riparian Vegetation Effects on Physical Characteristics of Riparian Zones of Midwestern Pastures

Grazing at high stocking rates May Increase sediment and nutrient loading of streams pasture Through Transport in precipitation runoff and bank erosion. A 3-yr (2007-2009) grazing study was Conducted on 13 cool-season grass pastures to quantify effects of stocking rate and botanical composition on forage sward height, proportions of bare and manure-covered ground, and bank erosion adjacent to streams. Pastures ranged from 2 ha to 107 ha with stream Reaches of 306 m to 1778 m That has drained watersheds of 253 to 5660 ha. Bare and manure-covered ground Were Measured at 15.2-m distance perpendicular to the stream at 30.5-m intervals at up to 30 locations on each side of the stream by the line transect method in May, July, September, and November of each year.At the midpoint of the 15.2-m line, forage sward height was Measured with a falling plate meter (4.8 kg · m -2 ) and plant species identified. In November 2006, fiberglass pins (1.6 × 76.2 cm) 73.7 cm Were driven into the stream bank at 1-m intervals from the streambed to the top of the bank along 10 transect equidistant locations on each side of the stream bank erosion to measure During spring, summer, and fall of each year. Increasing pasture stocking rates Increased manure-covered ground and Decreased sward height, but did not Affect proportions of bare ground. The greatest, intermediate, and Least net soil erosion rates occurred During the winter / early spring, late spring / early summer, and late summer / fall seasons. Stocking rates Between measurements, Expressed as cow-days · m -1 stream, Were not related to bank erosion. Increasing stocking rates per unit of stream length will cover manure Increase and decrease forage sward height, but not Affect proportions of bare ground or bank erosion rates pasture adjacent to streams.THEREFORE, managing stocking rates May reduce nutrient loading of streams pasture

Quantifying the role of riparian management to control non-point source pollution of pasture and cropland streams

Grazing management practices have the potential to mitigate some problems with sediment and phosphorus loading in pasture streams. The project demonstrated possible strategies to lessen grazing impacts on streams