bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessing Ecological Sustainability of Slash‐and‐Burn Agriculture through Soil Fertility Indicators
Authors: Kleinman Peter J. A. , Bryant Ray B. , Pimentel David 
Published: July 2010

AbstractThe objective of this study was to assess the near‐ and long‐term impact of traditional slash‐and‐burn agriculture on soil fertility in the village of Kembera, West Kalimantan, Indonesia. Soil fertility is widely viewed as one of the key limits to sustainable production in slash‐and‐burn agroecosystems. A chronosequence of sites ranging from currently cultivated swiddens to a 28‐yr fallow was surveyed. Organic C, cation exchange capacity (CEC), pH, nitrate, extractable basic cations, available and total P, and extractable Al were measured as indicators of soil fertility. Inferred short‐term trends point to significantly improved soil fertility conditions after burning in currently cropped swiddens relative to fallows. During the fallow, soil organic C, CEC, nitrate, total P, and extractable basic cations all manifest positive associations with fallow length after 3 to 11 yr of fallow. No declines in soil parameters were detected between plots based on the frequency of past slash‐and‐burn activity. Therefore, there is no evidence that slash‐and‐burn agriculture in Kembera has degraded these soil resources. While the results of this study suggest that slash‐and‐burn agriculture in Kembera has been ecologically sustainable, recent changes in socioeconomic factors influencing farmer's land‐use decisions cast doubt upon the future sustainability of this agroecosystem.
Evaluating Cotton Nitrogen Dynamics in the GOSSYM Simulation Model
Authors: Stevens William E. , Varco Jac J. , Johnson Joseph R. 
Published: July 2010

AbstractPrediction of cotton (Gossypium hirsutum L.) N requirements would be useful in preventing excessive vegetative growth and negative environmental effects from overapplication of fertilizer N. Field research studies were conducted at Holly Springs, MS, to evaluate early‐maturing and full‐season cultivar effects on N nutrition and yield. Cotton was grown across a range of N application rates and results were compared with simulations of the cotton model GOSSYM. Cotton cultivars Stoneville 825 and DES 119 were grown on a Grenada silt loam soil (fine‐silty, mixed, thermic Glossic Fragiudalfs) in 1989 and 1990, and Deltapine 20 on a Loring silt loam soil (fine‐silty, mixed, thermic Typic Fragiudalfs) in 1990, all with N rates of 0, 45, 90, 135, and 180 kg ha−1. Rainfall in May through September 1990 was only 52% of the rainfall during the same period in 1989. Cultivar effects on yield and cotton N nutrition were minimal. Averaged across cultivars and N rates, 24% of total plant N on the Grenada soil and 20% on the Loring soil in 1990 was in ground litter at first open boll, compared with 13% in 1989 on the Grenada soil. GOSSYM accurately predicted litter N for the Grenada site in 1990, but overpredicted N in litter in 1989 at this site and in 1990 for the Loring site. On the Grenada soil in 1989, an average of 61% of the total plant N at first open boll was in seed and burrs, while in 1990 it was 41%, due to a lower boll load. For both soils, N availability without fertilizer ranged from 68 to 77 kg N ha−1. GOSSYM overestimated soil N availability by 10 to 30 kg N ha−1. Averaged across cultivars on the Grenada soil in 1989, GOSSYM underpredicted yield on cotton with no fertilizer N by 463 kg lint ha−1. Fertilizer N recovery was overpredicted by the model. These results point to the need for more accurate prediction of N dynamics if the model is to be used for N management on fragipan soils.
Fusarium Head Blight in Hard Red Spring Wheat: Cultivar Responses to Natural Epidemics
Authors: Wiersma John V. , Peters Eugene L. , Hanson Mark A. , Bouvette Robert J. , Busch Robert H. 
Published: July 2010

AbstractFusarium head blight (FHB), caused primarily by Fusarium graminearum Schwabe, is an important but sporadic disease throughout major spring wheat (Triticum aestivum L.) production areas in Canada and the USA. Our objectives were to (i) examine the effects of years, planting dates, cultivars, and their interactions on FHB measures and agronomic traits and (ii) characterize cultivar responses across a range of environments. Eight planting dates and 16 hard red spring wheat cultivars were studied in field trials during 1993 and 1994 at Crookston, MN. Normal and above‐normal rain during June and July provided moist conditions during anthesis of most cultivars across several planting dates each year. Incidence and severity of FHB varied markedly with planting date, anthesis date, year, and cultivar. Cultivars that achieved higher than average grain yield and test weight over all environments did so because they performed well in environments that favored FHB. Cultivar mean grain yield (r = −0.75, P = 0.01) and test weight (r = −0.93, P = 0.01) were inversely correlated with cultivar mean FHB incidence. ‘Butte‐86’, ‘Grandin’, ‘Marshall’, and ‘Nordic’ generally had lower mean FHB incidence and severity and were less responsive to environments favorable for disease than other cultivars. These cultivars also had higher grain yield and test weight than most other cultivars. ‘Norm’, ‘Minnpro’, ‘Sonja’, and ‘Bergen’ were representative of more susceptible cultivars. They had higher levels of disease, were more responsive to environments favorable for disease, and had lower grain yield and test weight. Attempts to avoid FHB by varying planting date were not successful. Careful cultivar selection for tolerance to FHB should provide moderate increases in grain yield (10−20%) and test weight (5−10%) for spring wheat producers in northwest Minnesota.
Evaluation of Optimum and Above‐Optimum Phosphorus Supplies for Corn by Analysis of Plant Parts
Authors: Mallarino Antonio P. 
Published: July 2010

AbstractThe concentration of nutrients in the ear leaves of corn (Zea mays L.) often is used to evaluate the nutrient status of this crop. A recent report showed, however, that the P concentration of ear leaves does not evaluate excess P supplies appropriately. This study evaluated the capacity of tests based on the P concentrations of four plant parts to evaluate the P status of corn in soils testing in the optimum to above‐optimum availability range. The plant parts tested were young plants (at V5 to V6 growth stages), ear‐leaf blades at silking, lower stalk sections after physiological maturity, and harvested grain. Grain yields and tissue samples were collected from plots of 25 field trials in Iowa. Treatments were 0, 25, 50, and 75 kg P ha−1. There was a significant yield response to P at 6 sites. The P treatments increased the P concentrations of young plants at 5 sites, of leaves at 13 sites, of stalks at 3 sites, and of grain at 11 sites. Differences in tissue P concentrations among sites often were greater than differences among treatments. Relationships between grain yield response and P concentrations of the tissues showed that P deficiency usually was correctly identified by tests of young plants and leaves. Determined critical concentrations were 3.4 g P kg−1 for plants and 2.4 g P kg−1 for leaves. The P concentrations of plants and leaves increased with soil‐test P until a plateau was reached, which suggests that these tissues have upper limits for luxury accumulation of P. The limits for young plants and for leaves occurred at soil‐test P values only slightly higher than values needed to obtain maximum economic yields of corn. The P concentrations of stalks were not related to yield responses or soil‐test P. Luxury accumulation of P in grain had no clear upper limit but P concentrations were very poorly related with yield responses or soil‐test P. The results showed that tests based on the P concentrations of young plants and ear leaves have similar capacities for identifying severe P deficiencies. None of the four tests evaluated would be a reliable diagnostic tool to evaluate P supplies for corn in the optimum to above optimum availability range.
Potential Carbon Sequestration by Afforestation of Pasture in the South‐Central United States
Authors: Lee Jeffrey J. , Dodson Rusty 
Published: July 2010

AbstractClimate models indicate that increasing atmospheric concentrations of CO2 and other greenhouse gases could alter climate globally. The Climate Change Action Plan commits the USA to reducing net greenhouse gas emissions by 106 ✕ 106 Mg C yr−1 by the year 2000. One suggestion for reducing net emissions is to convert marginal grass pastures to pine (Pinus spp.) plantations in the South‐Central USA. We used the Erosion/Productivity Impact Calculator (EPIC) model to estimate the amount of atmospheric C that could be sequestered by this suggested change in land use. Carbon flow dynamics at each of 100 randomly selected sites were simulated for 50 yr under two assumptions: (i) continuous pasture for 50 yr or (ii) pine plantations harvested every 25 yr. Carbon sequestered by conversion to pine plantations was calculated as the net change in off‐site storage (i.e., in long‐lived products and landfills), plus the change in soil organic C, plus (for the first harvest period) stand establishment. Average C‐sequestration (±SE) was 40 ± 2 and 18 ± 2 Mg C ha−1 for the first and second 25‐yr harvest periods, respectively. In contrast, sequestration would have been 8.3 ± 0.6 Mg C ha−1 as soil organic C if the sites had been left in continuous pasture for 50 yr, or 3 Mg C ha−1 after correcting for release of C during manufacture of N‐fertilizer. Extrapolated to the region, conversion of 3.6 × 106 ha of marginal grass pasture to pine plantations could sequester 5.6 × 106 C yr−1 for the first 25 yr and 1.1 × 106 Mg for the second 25 yr. If all types of marginal agricultural land in the region (4.6 × 106 ha) were converted to forestry, the corresponding sequestration rates would be 7.4 × 10,6 and 1.4 × 106 Mg C yr−1 . In contrast, maintaining the land in continuous pasture would sequester 0.3 × 106 Mg C yr−1.
Model of Leaf Area Expansion in Field Pea Subjected to Soil Water Deficits
Authors: Lecoeur Jérémie , Wery Jacques , Sinclair Thomas R. 
Published: July 2010

AbstractYield of field pea (Pisum sativum) is sensitive to soil water deficits. An important component of this sensitivity is the response of leaf area to drought. A simple, mechanistic model was developed to allow predictions of leaf area development in response to soil water deficits. The model calculates leaf areas of individual drought‐stressed leaves relative to leaves on well‐watered plants as the product of the number of cells and the size of the cells. Therefore, distinct phases of cell division and cell expansion were identified and temporally distinguished in the model. Cell division and cell expansion in the model were both sensitive to the fraction of transpirable soil water. The model proved capable of predicting the temporal development and the final area (r2 = 0.91) of individual leaves on pea plants in response to soil water deficits.
Frost‐Seeding Legumes into Established Switchgrass: Forage Yield and Botanical Composition of the Stratified Canopy
Authors: Gettle Randall M. , George J. Ronald , Blanchet Kevin M. , Buxton Dwayne R. , Moore Kenneth J. 
Published: July 2010

AbstractGrasses need adequate N for optimum herbage yield. Legumes could be grown in mixed swards with switchgrass (Panicum virgatum L.) to provide symbiotic N and replace the need for N fertilization, extend the growing season because C3 species begin growth earlier and continue growth later into the growing season, and increase dry matter (DM) yield. The objective of this field study on a Webster‐Nicollet soil (fine‐loamy, mixed, mesic, Typic Haplaquoll‐Aquic Hapludoll) at Ames, IA, was to compare herbage DM yield and botanical composition for legume‐renovated switchgrass with that of N‐fertilized switchgrass. Five inoculated forage legumes and a legume mixture were frost‐seeded into an excellent stand of established ‘Cave‐in‐Rock’ switchgrass in mid‐March of 1991 and 1992. Grass‐legume DM yield was compared with N fertilization (0, 60, 120, and 240 kg ha−1) in the seeding year (YR 1) and the second year (YR 2). Harvested samples were separated into grass and legume components, and further divided into upper and basal canopy. Nitrogen fertilization provided greatest upper and basal canopy yields in both June and July of YR 1. By June YR 2, legume renovation increased upper‐canopy yields more than for 240 N. Upper‐canopy YR 2 yields of grass‐legume mixtures seeded in 1991 remained greater than for 240 N in July, and were similar to 120 N in August. During a wetter and cooler than normal summer, YR 2 yields of upper‐canopy grass‐legume mixtures seeded in 1992 were similar to 60 and 120 N by July, and similar to both unfertilized and N‐fertilized switchgrass by August. We concluded that yields of legume‐renovated switchgrass were generally greater than for mid to high levels of N fertilization during YR 2. Because of relatively low herbage production during YR 1, producers should consider frost‐seeding legumes into only part of existing switchgrass pastures, while fertilizing the remaining nonrenovated pasture with N to maintain high forage supply and pasture productivity.
Soybean Seedling Emergence Influenced by Days of Soil Water Stress and Soil Temperature
Authors: Helms Theodore C. , Deckard Edward , Goos Robert J. , Enz John W. 
Published: July 2010

AbstractSoybean [Glycine max (L.) Merr.] producers often plant into a dry seed bed rather than waiting until soil water conditions are optimum for germination and emergence. In some cases, there is sufficient water for imbibition, but not enough for germination. Producers need to know how long seeds can remain viable under this type of stress. Our objective was to evaluate, under controlled conditions, the influence of soil temperature, soil water content, and duration of stress on soybean emergence and seedling development. Our experiment consisted of a factorial combination of (i) three temperatures regimes (low, 17/8°C day/night; medium, 21/12°C, and high, 25/16°C), (ii) four gravimetric soil water contents (0.07, 0.09, 0.11, and 0.13 kg kg−1), and (iii) three stress durations (0, 6, and 12 d). Soil water content influenced seedling development and emergence, and there was a significant temperature ✕ soil water interaction for both traits. Length of stress also influenced seedling development and emergence. In general, emergence was poor after 12 or more days of soil water conditions that allowed seeds to imbibe water, but were too dry to allow the radicle to emerge from the testa. Under these conditions, seedling emergence decreased as soil temperature increased. Producers can use this information regarding the length of stress interval at a given seed stage as indication of when replanting would be necessary.
Allocation and Cycling of Nitrogen in an Alfalfa‐Bromegrass Sward
Authors: Walley Frances L. , Tomm Gilberto O. , Matus Alejandro , Slinkard Alfred E. , van Kessel Chris 
Published: July 2010

AbstractThe N requirements of grasses grown in legume‐grass mixtures can be met in part via transfer of symbiotically fixed N from the legume to the nonlegume. The objectives of this study were to determine above‐ and belowground biomass production and N accumulation of alfalfa (Medicago sativa L.) and meadow bromegrass (Bromus riparius Rhem.) in a mixed stand and to investigate N cycling between these species. Available soil inorganic N was monitored and biomass production and N accumulation were determined over 3 yr. Symbiotic N2 fixation and N transfer were estimated using 15N‐enriched isotope dilution, natural 15N abundance, and N‐difference methods. Both species depleted available soil N to comparable levels (less than 5 mg kg−1 soil). Following the establishment year, the majority of alfalfa N was allocated to aboveground plant production, whereas N‐stressed meadow bromegrass favored belowground allocation. Estimates of the proportion of N derived from fixation in alfalfa using 15N‐enriched isotope dilution and N‐difference methods ranged from 74 to 89%, and 76 to 93%, respectively, after the establishment year. Use of the natural 15N abundance method resulted in consistently lower estimates of N2 fixation as compared with the 15N‐enriched isotope dilution and N‐difference methods. The average potential annual net N input was 86 kg N ha−1 in the mixed sward and 168 kg N ha−1 in monocropped alfalfa. Maximum net transfer of N from alfalfa to meadow bromegrass, estimated using 15N‐enriched isotope dilution, was 55 kg ha−1. Evidence suggests that N transfer largely occurred indirectly via net N mineralization of belowground plant components.
Effect of Phosphorus Soil Test Level on Sorghum‐Sudangrass Response to Phosphorus Fertilizer
Authors: Bauder James W. , Mahmood Shaukat , Schaff Bernard E. , Sieler David J. , Jacobsen Jeffrey S. , Skogley Earl O. 
Published: July 2010

AbstractMany agricultural soils of the northern Great Plains have excess CaCO3 or CaSO4 and pH levels above 7.8, thereby having high fixation capacity for applied P and resultant poor predictability of crop responses to applied P fertilizer. In addition, initial and residual effects of applied fertilizer P on soil test P values are not well understood. A greenhouse study was conducted with Sordan 79 (sordan), an intraspecific [Sorghum bicolor (L.) Moench] sorghum‐sudangrass hybrid [syn. S. bicolor‐S. sudanense (Piper) Stapf], on three soils with different textures, cation exchange capacities, and CaCO3 contents to determine sordan response to P fertilizer applied to calcareous soils. Soil test P (bicarbonate‐extractable) was adjusted to five initial levels, ranging from 2 to 60 μg P g−1 soil. Fertilizer P was then applied at five levels, ranging from 0 to 40 mg P kg−1 soil. Three successive harvests of the test crop were completed and measurements of dry matter were made. Response surfaces and regression models were developed, describing the relationships among sordan yield, P uptake by the crop, total P applied as fertilizer, and resultant soil test P values. Sordan response to P fertilizer was linear at soil test values of <30 μg P g−1 soil, but the response was curvilinear above soil test values of 30 μg P g−1 soil. However, soils with lower soil test levels did not yield as much, even at the highest P rates, as those soils testing above 30 μg P g−1 soil and with no additional P added. The preplant soil test P concentrations as well as the residual (postexperiment) bicarbonate‐extractable P soil test concentrations increased with increasing rate of fertilizer P. Results of this study suggest advantages of fertilizer strategies that elevate the bicarbonate‐extractable P soil test values of agricultural soils having excess CaCO3 and pH values above 7.8. Only maintenance applications of fertilizer P appear to be necessary when soil test P concentrations are at or above 30 μg P g−1 of soil and these same soils have relatively high CaCO3 or CaSO4 concentrations.
Strip Intercropping and Nitrogen Effects on Seed, Oil, and Protein Yields of Canola and Soybean
Authors: Ayisi Kingsley K. , Putnam Daniel H. , Vance Carroll P. , Russelle Michael P. , Allan Deborah L. 
Published: July 2010

AbstractIncreased world demand for high‐quality edible oil requires agronomic practices that increase oilseed yields with minimal environmental impact. We hypothesized that strip intercrops of canola (Brassica napus L.) and soybean [Glycine max (L.) Merr.] would increase seed, oil, and protein yields compared with sole crops. Canola (cv. Global) was grown in 4.5‐m wide strips adjacent to 4.5‐m strips of later‐planted soybean (cv. Chippewa) at Rosemount, MN, in 1991 and 1992, and at St Paul, MN, in 1992. Zero or 134 kg N ha−1 was applied at planting in the Rosemount studies, and 134 kg N ha−1 was applied at St. Paul. Seed yield, oil, and crude protein (CP) concentrations were determined for individual rows. Land equivalent ratios (LER) were calculated, using inner rows of the strip to represent sole crop yields. Canola border row yields were 225 to 590% of those of sole crop rows. Without N fertilization, soybean border row yields were similar to sole crop rows, but with added N fertilizer were only 50 to 65% of the sole crop yields. Projected LERs (range: 1.02 to 1.65) were significantly greater than 1.0 for strip widths of 1 to 4 m without N, and 1 to 6 m with fertilizer N. Strip intercrops produced edible oil and CP yields up to 170% of the mean of the two sole crops. Intercropping canola and soybean in strips has the potential to reduce fertilizer applications and enhance oil and protein yields compared with sole crops.
Structure and Reflectance of Irrigated Cotton Leaf Canopies
Authors: Maas Stephan J. 
Published: July 2010

AbstractAssessing the condition of an agricultural crop through remote sensing and crop modeling requires knowledge of crop characteristics related to plant canopy structure and reflectance. A study was conducted to characterize the structure and reflectance of cotton (Gossypium hirsutum L.) leaf canopies over 3 yr using detailed physical and spectroradiometric measurements. Three canopy characteristics (leaf canopy reflectance, width, and height) were measured in several fields in southern Texas and in one field in Arizona. Canopy reflectance in the near‐infrared was independent of canopy density, while canopy reflectance at red wavelengths was only slightly affected by canopy density. Reflectance appeared to involve primarily the top layer of leaves in the cotton canopy. Canopy width, when normalized by leaf area per plant and plant spacing, could be fit with a single relationship for all locations and years. A single relationship was also found to apply to canopy height. The consistency of these characteristics between locations and years suggests that they might be incorporated into physiology‐based cotton models to allow explicit simulation of canopy reflectance.
Tall Fescue Response to Clipping and Competition with No‐Till Seeded Alfalfa as Affected by Fungal Endophyte
Authors: Hoveland Carl S. , Durham Robert G. , Bouton Joseph H. 
Published: July 2010

AbstractTall fescue (Festuca arundinacea Schreb.) is generally less productive, persistent, and competitive under stress after removal of its fungal endophyte, Neotyphodium coenophialum (Morgan‐Jones & W. Gams) Glenn, Bacon & Hanlin (syn. Acremonium coenophialum Morgan‐ Jones & W. Gams). Our objectives were to compare endophyteinfected (E + ) and endophyte‐free (E −) tall fescue for (i) forage yield and tiller response at different cutting frequencies and heights and (ii) competition with no‐till seeded alfalfa (Medicago sativa L.). Factorialized combinations of 3‐wk and hay‐stage harvest intervals with clipping heights of 3.8 cm (low) and 7.6 cm (high) were used with E + and E − tall fescue in a 4‐yr study. ‘Alfagraze’ alfalfa was no‐till seeded into E + and E − ‘Kentucky 31’ tall fescue, E − ‘AU Triumph’ tall fescue, orchardgrass (Dactylis glomerata L.), reed canarygrass (Phalaris arundinacea L.), and Kentucky bluegrass (Poa pratensis L.) in each of 3 yr. Forage yield of E + and E − Kentucky 31 was similar (P > 0.05) within a cutting treatment. When cut at 3‐wk intervals, a low as compared with a high clipping height had no effect (P > 0.05) on total forage yield of E + Kentucky 31 tall fescue, but forage yield of E − Kentucky 31 and E − AU Triumph were reduced by 23 and 28%, respectively, in the fourth year. Both E + and E − tall fescue cut every 3 wk during a dry, hot summer at a low clipping height had autumn forage yields only 20 to 25% of that at a high clipping height. Tiller populations declined more on AU Triumph than E − Kentucky 31 in response to cutting. Cutting height had a minor effect on yield with hay‐stage harvest. Endophyte infection had no effect on stands or forage yield of no‐till seeded alfalfa. Alfalfa forage yields were lower with tall fescue than with the other grass species. AU Triumph, a winter‐productive tall fescue, was the grass most competitive with alfalfa.