bluuebunny/crossref_metadata_2025 huggingface dataset:
A General System to Measure and Calculate Daily Crop Water Use
Authors: Lascano Robert J.
Published: July 2010

There is a need for an accurate method to calculate and to measure crop water use on real‐time. We implemented a system that combines knowledge of crop water use and available technology to control the timely application of water. Our objective was to test the system and compare it to the empirical engineering approach that uses a crop coefficient to relate crop water use to a reference evapotranspiration. Technologies involved are the measurement of plant water use with stem flow gauges, of soil water with time domain reflectometry, and weather variables. Measurements are coupled with calculated values of crop water use obtained with the model ENWATBAL. A single computer controls all functions, for example, measurements, model execution, activation of water delivery system. The system was tested for a 2‐yr period with cotton (Gossypium hirsutum L.) in Lubbock, TX, using surface drip irrigation. Field experiments were conducted on an Olton clay loam (fine, mixed, superactive, thermic Aridic Paleustolls). Comparison of measured and calculated values of crop transpiration and soil water evaporation were in close agreement. Simulated results indicated that for a 3‐d frequency irrigation with small quantities of water the engineering approach lacks the resolution to accurately calculate daily requirements of cotton under the semiarid conditions of the Texas High Plains (THP). This is particularly true early in the growing season when predominant evaporative losses are from the soil and not from the crop. We conclude that the proposed system is general and can be applied to schedule irrigations based on accurate estimates of water loss.
A Two‐Source Energy Balance Approach Using Directional Radiometric Temperature Observations for Sparse Canopy Covered Surfaces
Authors: Kustas William P. , Norman John M.
Published: July 2010

A two‐source energy balance model developed to use directional radiometric surface temperature for estimating component heat fluxes from soil and vegetation has had several recent modifications to account for some of the unique properties associated with sparse canopies. Two of these changes involve the algorithms predicting the divergence of net radiation inside the canopy and how to account for clumped vegetation, which affects both the wind and radiation penetration inside the canopy and radiative temperature partitioning between soil and vegetation components. Model results with and without these modifications are compared using data collected from a sparsely vegetated row crop of cotton (Gossypium hirsutum L. cv. Delta Pine 77). It is suggested that these two new algorithms be incorporated in any two‐source model applied to sparse canopies.
Sugarcane Genotype Response to Phosphorus Fertilizer in the Everglades
Authors: Glaz Barry , Powell Gerald , Perdomo Raul , Ulloa Modesto F.
Published: July 2010

To protect the natural Everglades, federal legislation mandates a reduction of at least 25% in the P content of water discharged from the Everglades Agricultural Area (EAA). Work is needed to achieve these reductions while sustaining a productive agriculture in the EAA. The objective of this study was to identify differences in response to P fertilizer among 24 elite genotypes of sugarcane (interspecific hybrids of Saccharum spp.). Six yield characteristics were examined on Histosols at four field locations with no added P, an often used commercial rate of 24 kg P ha−1, and 48 kg P ha−1 for the plant‐cane, first‐ratoon, and, in three locations, the second‐ratoon crop. One group of eight genotypes was planted at two locations, and two other groups of eight genotypes each were planted at one of two other locations. Genotype × P fertilizer rate interactions were generally not significant. Of the eight genotypes tested at two locations, CL 61‐620, CP 72‐2086, and CP 85‐1308 were cautiously (P ≤ 0.15) identified at both locations as more sensitive than other genotypes to changes in P rates. Reduced P rates were recommended for CP 85‐1308 on soils with low P. CL 73‐239 and CP 81‐1254 required more than commonly recommended P fertilizer on low‐P soils. Identification of sugarcane genotypes that respond favorably to varying rates of P may evolve into a cost‐effective strategy to reduce P content of EAA drainage water.
Forage Yield Precision, Experimental Design, and Cultivar Mean Separation for Alfalfa Cultivar Trials
Authors: Casler Michael D. , Undersander Daniel J.
Published: July 2010

As alfalfa (Medicago sativa L.) cultivars have become more numerous in recent years, the issue of precison of alfalfa forage yield determinations has become more important. The objective of this study was to develop a set of recommendations for improving the precision of alfalfa cultivar forage‐yield estimates. Inferences were derived from 49 alfalfa cultivar trials conducted at 13 Wisconsin locations between 1984 and 1996. Although randomized complete block designs were sometimes effective, spatial analysis offers considerable potential for improved precision. Increasing the number of replicates was expected to be more effective than increasing plot size. Trial data should be discarded only when severe and irreversible biological or physical disturbances are present. If researchers feel the need to discard data or entire trials on the basis of low statistical precision as an additional criterion, the decision should be based on (i) nonsignificant F‐tests for cultivars of all individual years and for the combined over‐years analysis or (ii) an unusually high mean square error relative to the trial mean or range among cultivar means. Trial data should not be rejected based on the coefficient of variation (CV). Genotype × environment interactions followed patterns based largely on expectations of edaphic and climatic environmental differences. Inherent precision of alfalfa cultivar trials did not influence cultivar rankings per se.
Herbage Accumulation of Three Bahiagrass Populations during the Cool Season
Authors: Gates Roger N. , Mislevy Paul , Martin Frank G.
Published: July 2010

Fall and winter are periods of critical forage shortage in subtropical regions of the world, including the extreme southeastern USA. Cool‐season herbage accumulation has not been documented for bahiagrass [Paspalum notatum Flügge var. saurae Parodi] that has been selected using recurrent restricted phenotypic selection (RRPS) for increased warm‐season yield. Regrowth of ‘Pensacola’, ‘Tifton 9’, and RRPS Cycle 18 that accumulated for 15 or 30 d was harvested from mid‐September through mid‐April at Tifton, GA and Ona, FL for 2 yr. Herbage accumulation was essentially parallel for the three populations; minimums were coincident in midwinter, and maxima generally occurred at the first autumn harvest or last spring harvest. Fall and spring yields of Tifton 9 and RRPS Cycle 18 were generally higher than those of Pensacola and often more than double. This advantage was more pronounced at Ona than Tifton. Digestibility (600 g kg−1) and crude protein (CP) concentration (150 g kg−1) at Ona remained high throughout the cool season. However, forage quality of bahiagrass at Tifton tended to decrease with increased frosts. Cool‐season growth of three bahiagrass populations was slow, but RRPS selection has led to populations with greater growth potential, except when cold temperatures prohibit growth entirely.
Path Analyses of Population Density Effects on Short‐Season Soybean Yield
Authors: Ball Rosalind A. , McNew Ronald W. , Vories Earl D. , Keisling Terry C. , Purcell Larry C.
Published: July 2010

Yield component analysis provides a framework for identifying potentially useful traits for yield improvement. Consideration of how population density affects other yield components has not been addressed specifically for short‐season soybean [Glycine max (L.) Merr.] production. We assessed the direct and indirect contributions of population density for short‐season soybean yield and its components over a wide range of population densities (6–134 plants m−2) using path‐coefficient analysis. Data were from field tests conducted in 1997, 1998, and 1999 at Keiser, AR. Although population density had a large inverse association with pods plant−1, the large direct effect of population density on yield was greater than its negative indirect effect via pods plant−1. The direct effects of pod number plant−1 and seeds pod−1 on yield were positive, whereas mass seed−1 had a negligible effect. Pods fertile‐node−1 differed between cultivars, and it was reduced by increasing population density. For early sowing, the contribution of population density to yield was less because pods m−2 could be achieved at low population densities by a large number of fertile‐nodes plant−1 and pods fertile‐node−1. In contrast, at late sowing, the decreased potential for fertile‐nodes plant−1 was compensated by increasing plant population density. In short seasons, maximizing nodes m−2 and pods m−2 can be achieved by high population densities and early canopy closure, rather than the conventional system of larger plants with greater numbers of pods plant−1 and pods fertile‐node−1
Alternative and Opportunity Dryland Crops and Related Soil Conditions in the Southern Great Plains
Authors: Unger Paul W.
Published: July 2010

Dryland winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] yield favorably when rotated or grown continually in the southern Great Plains, but improved water conservation practices make other systems possible for these crops. Also, farmers can now produce other crops without losing government payments. Winter wheat, grain sorghum, and opportunity crop performance; alternative crop adaptability; and system effects on soil properties were determined. Wheat yielded 1.82 Mg ha−1 when rotated with grain sorghum or fall canola (Brassica napus L.) and 1.21 Mg ha−1 when grown continually or rotated with spring canola. Soil water contents at planting resulted in the differences. Grain sorghum yielded 2.89 and 3.02 Mg ha−1 when rotated with wheat or grown continually and 2.24 Mg ha−1 when rotated with kenaf (Hibiscus cannabinus L.), although water contents at planting were similar. Kenaf produced only 2.3 Mg ha−1 plant material, but contained 327 g kg−1 protein at 32 d after planting and 195 g kg−1 when killed by frost. Canola crops failed. Triticale (× Triticosecale Wittmack) produced more forage, but less grain than wheat. Soil water contents at planting and precipitation strongly influenced opportunity crop yields. Mean soil C contents increased from 5.52 to 5.94 g kg−1 during the study. Aggregate diameters and percentages <0.25 mm in diameter showed no definite trends. Few bulk density and no aggregate water stability results differed. Some alternative and opportunity crops produced favorably, but generally no better than wheat or grain sorghum.
Allelopathy of Aspergillus japonicus on Crops
Authors: Zeng Ren Sen , Luo Shi Ming , Shi Mu Biao , Shi Yue Hong , Zeng Qiang , Tan Hui Fen
Published: July 2010

The seeds of some dicotyledons fail to germinate and grow well when contaminated by Aspergillus japonicus Saito. One strain of A. japonicus isolated from the seeds of contaminated rape (Brassica campestris L.) inhibited the seedling growth of rape and radish (Raphanus sativus L.) when the fungus was directly inoculated on the seed surface. Metabolites released from the fungus inhibited the seedling germination and seedling growth of rape and radish. The culture filtrate and mycelium acetone (C3H6O) extract inhibited the seedling growth of rape. The major allelochemical of A. japonicus was identified by spectroscopic methods as secalonic acid F (SAF). Bioassays showed that SAF at concentration 0.038 mM significantly inhibited the seedling growth of several crops.
Frost Seeding into Aging Alfalfa Stands
Authors: Undersander Daniel J. , West David C. , Casler Michael D.
Published: July 2010

Little is known about the potential to frost‐seed cool‐season pasture species into mature alfalfa (Medicago sativa L.). Experiments were conducted in 1995 and 1996 near Arlington, WI (four sites), and Lancaster, WI (three sites), to evaluate the establishment and response to seeding rates of five cool‐season grasses and red clover (Trifolium pratense L.) frost‐seeded into mature alfalfa (2‐ to 5‐yr‐old stands with 30 to 50 plants m−2). Smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), perennial ryegrass (Lolium perenne L.), reed canarygrass (Phalaris arundinacea L.), timothy (Phleum pratense L.), and red clover were frost‐seeded into mature alfalfa stands at six seeding rates. Orchardgrass, perennial ryegrass, and red clover had higher densities and responses to seeding rate than smooth bromegrass, timothy, and reed canarygrass in the seeding year, but these differences were less pronounced in the postseeding year. Orchardgrass contributed more grass dry matter in the seeding year but was similar to smooth bromegrass and timothy and greater than perennial ryegrass and reed canarygrass in the second year. Alfalfa and weed suppression were highest with orchardgrass due to its aggressive growth habit, high occurrence, and winterhardiness. Postseeding–year mixture yields were high for smooth bromegrass, orchardgrass, timothy, and reed canarygrass, but low for perennial ryegrass and red clover. Forage yield increased with seeding rate at sites with the greatest initial establishment. The results of this study suggest frost seeding temperate pasture species into mature alfalfa can increase plant diversity and forage yield while suppressing weeds.
Tillage and Previous Crop Effects on Dynamics of Nitrogen in a Wheat–Soil System
Authors: Soon Yoong Kee , Clayton George W. , Rice Wendell A.
Published: July 2010

The effects of tillage and preceding legume crops on N flux in the soil–plant system require quantification for developing sustainable cropping systems. We measured changes in soil and plant N under the influence of tillage [no till (NT) vs. conventional tillage (CT)] and previous crops [spring wheat (Triticum aestivum L.), red clover (Trifolium pratense L.) green manure, and field pea (Pisum sativum L.)]. The study was conducted from 1994 through 1996 on a well‐drained sandy loam soil (coarse‐loamy, mixed, frigid, Typic Cryoboralf) near Fort Vermilion, Alberta (58°23′N, 116°2′W). Nitrogen uptake by wheat was increased by NT and legume crops. At seeding, CT soil had 28 kg ha−1 more NO3–N to 100‐cm depth than NT soil. Apparent net N mineralization in the growing season was 71 and 22 kg N ha−1, respectively, for the NT and CT systems. Previous crop effect on net N mineralization (kg N ha−1) was red clover (56) > field pea (51) > wheat (34). Approximately 18 kg N ha−1 was net‐mineralized from red clover residues compared with insignificant amounts from pea and wheat residues. Microbial biomass turnover's contribution to net N mineralization (28 to 40 kg N ha−1) was increased by NT and previous legume crop. Soluble organic N decreased by 7 kg ha−1 between seeding and maturity for all experimental treatments. The results indicate that N fertilizer recommendations should allow for greater mineralization of organic N under NT than CT and following a legume green manure.
Minirhizotron Observations of the Spatial Distribution of the Maize Root System
Authors: Liedgens Markus , Richner Walter
Published: July 2010

The vertical and horizontal distribution of maize (Zea mays L.) roots was studied using minirhizotrons in drainage lysimeters for 3 yr. Ten minirhizotrons (60‐mm o.d.) were placed horizontally at depths of 5 to 100 cm, perpendicular to the maize row. Root density (roots cm−2) on minirhizotron images (2.43 cm2) was observed at leaf developmental stages 3, 6, 9, and 12 and at pollen shed. Root density increased to a maximum at 25‐cm depth and decreased at greater depths. This pattern was observed in all years and at all developmental stages except for early in the season. The density of roots decreased with increasing distance from the plant row. Soil depth influenced root density more than the distance from the plant row, and its pattern was more complex. Root density was influenced by an interaction between both factors. Significant interactions of the spatial components of root density with maize developmental stage, but not with years, were identified although years strongly influenced maize leaf area. These results suggest that there is a basic pattern of maize root distribution in the soil, which is modified, but not fundamentally changed, by the ability of the roots to adapt to varying environmental conditions. Our results also indicated that the maize crop can explore soil resources only to a limited extent at early developmental stages, in deep soil layers, and at increasing distances from the plant row.
Forage Quality of Tall Fescue across an Irrigation Gradient
Authors: Asay Kay H. , Jensen Kevin B. , Waldron Blair L. , Han Guodong , Johnson Douglas A. , Monaco Thomas A.
Published: July 2010

Water available for irrigating pastures in the western USA is often limited and varies widely across sites and seasons. Objectives were to determine the trends in crude protein (CP), neutral detergent fiber (NDF), and in vitro true digestibility (IVTD) of 10 cultivars of tall fescue (Festuca arundinaceae Schreb.) at five levels of irrigation and three harvest dates (early, mid‐, and late season). A secondary objective was to evaluate the effect of the endophytic fungus [Neotyphodium coenophialum (Morgan‐Jones & Gams) Glenn, Bacon & Hanlin] on these trends. Cultivars differed significantly for CP, NDF, and IVTD, and differences were generally consistent across water levels (WLs). Concentration of CP increased in a near linear manner (154–189 g kg−1) from the highest to lowest WL; however, total protein yield decreased from 611 to 447 kg ha−1 with less water, closely following the trend in forage yield. Forage quality at the late‐season harvest, as indicated by lower NDF and higher IVTD values, was significantly higher at the lowest compared with the highest WL. Also, NDF was significantly lower and IVTD significantly higher at the late‐season harvest at all WL. Presence or absence of the endophyte was not associated with CP; however, there was a tendency for the endophyte‐free cultivar to have lower NDF and higher IVTD than its endophyte‐infected counterpart at the higher WL. The magnitude of quality differences among the 10 cultivars indicates that forage quality should be a major consideration in the choice of cultivars for pastures of the Intermountain region.
Crude Protein Fractionation and Degradation Parameters of Limpograss Herbage
Authors: Newman Y. C. , Sollenberger L. E. , Kunkle W. E. , Bates D. B.
Published: July 2010

Limpograss [Hemarthria altissima (Poir.) Stapf & Hubb.] has low crude protein (CP), but little is known about the plant's CP composition and degradation characteristics. Concentration of CP fractions A, B, and C were measured and the lag phase and rate and extent of CP degradation determined for herbage from two layers (upper 25% and next lower 50%) of limpograss canopies grazed at three heights (20, 40, and 60 cm) under continuous stocking. Slowly degradable (Fraction B) CP concentration in the dry matter (DM) was greater for the upper (21 g kg−1) than the lower (14 g kg−1) layer, and undegradable Fraction C concentration in total CP was greater in the lower (273 g kg−1) than in the upper (208 g kg−1) layer. Soluble Fraction A concentration was greatest for 20‐cm canopies, Fraction B concentration was greatest for the 40‐cm height CP basis. Fraction A concentrations in herbage CP were high across canopy heights (440–630 g kg−1), and Fraction B concentrations ranged from 190 to 310 g kg−1. Lag time of CP degradation ranged from 16 (20 cm) to 21 h (60 cm). Data suggest that (i) low total CP in the DM, resulting in low concentrations of Fractions A and B in the rumen, and the long lag phase for degradation of the B fraction contribute to protein deficiencies of cattle (Bos spp.) grazing limpograss and that (ii) grazing intensity affects forage N status, with highest concentration of N fractions that are available for rumen microbial utilization associated with closely (20 cm) grazed canopies.
Spatial Yield Response of Two Corn Hybrids at Two Nitrogen Levels
Authors: Katsvairo Tawainga W. , Cox William J. , Van Es Harold M. , Glos Michael
Published: July 2010

The challenge for variable N rate management is to identify specific field areas that respond to specific N levels. We evaluated two corn (Zea mays L.) hybrids at two N rates (110–130 vs. 165–185 kg ha−1 at three sites and manure vs. manure + 55 kg ha−1 at two sites) to determine if corn responded differently to N and hybrids within fields. Spatial yield variability existed at all sites in dry years (1999 and 2001) but at only two sites in a wet year (2000). Spatial yield difference variability in response to N existed at only two of 13 site–year comparisons. Although late‐spring soil NO3–N concentrations in the upper 30 cm were <25 mg kg−1 on 15 to 25% of the manured fields in the wet year, spatial yield difference variability in response to N did not exist. At a nonmanured site, spatial yield difference variability in response to N existed with temporal yield stability across dry years (r = 0.96). Surprisingly, corn responded to the higher N rate on 25% of this field where yields were least, but not where yields were greatest. Apparently, variable N rate management of corn requires more information than soil NO3–N concentrations and yield maps. Spatial yield difference variability between hybrids existed at only four of 15 site–year comparisons, despite hybrid interactions with sites. Adoption of variable hybrid selection is unlikely if hybrids that show interactions with sites do not show spatial yield difference variability within sites.
Scaling Effects of Standing Crop Residues on the Wind Profile
Authors: Aiken R. M. , Nielsen D. C. , Ahuja L. R.
Published: July 2010

Standing senescent stems increase the aerodynamic roughness of the surface, reducing wind energy available for momentum transfer at the soil surface, such as for wind erosion, and also the soil–atmosphere convective exchanges of heat, water vapor, and trace gases. We conducted studies to determine the predictive accuracy of an algorithm derived for plant canopies to scale effects of standing crop residues on the wind profile. We used this algorithm to calculate aerodynamic properties (displacement height and roughness length) of standing crop residues related to the log wind profile equation. We also calculated apparent roughness length from wind profiles measured under neutral stability conditions over stems of wheat (Triticum aestivum L.), corn (Zea mays L.), millet (Panicum miliaceum L.), and sunflower (Helianthus annuus L.) using calibrated single‐needle and cup anemometers. A least‐squares fit of roughness length calculated by an algorithm derived for crop canopies indicated a systematic, positive bias when it was applied to standing stems. After adjusting for bias, calculated windspeeds generally were contained in 80% confidence intervals for observations above and within the crop stubble. Predictive root mean square errors (RMSE) within profiles ranged from 0.6 to 4.6% of reference wind speed. The nonlinear forms of the scaling algorithms are consistent with theory and wind tunnel observations, representing an advance over parameterization schemes assuming a linear relation with residue height. This advance warrants evaluation of the adjusted algorithm for simulation of microclimate in the soil–residue–crop canopy regime. Application to momentum transfer problems requires further investigation of drag partitioning.
Influence of Alley Crop Environment on Orchardgrass and Tall Fescue Herbage
Authors: Burner David M.
Published: July 2010

The design of agroforestry systems requires a thorough understanding of biological interactions that might complement or constrain production. The objective of this study was to examine effects of alley crop environment on persistence, herbage yield, nutritive value, and gas exchange (CO2 exchange rate, transpiration, and stomatal conductance) of two shade‐tolerant herbage grasses. The experiment was conducted for 3 yr in orchardgrass (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.), and a 1:1 binary mixture (tall fescue and orchardgrass) in 4.9‐m‐wide alleys of 10‐yr‐old loblolly pine (Pinus taeda L.) and shortleaf pine (P. echinata Mill.), and the unshaded control at Booneville, AR. Loblolly pine was 1.5 m taller and had twice the canopy cover as shortleaf pine (52 and 25% canopy cover, respectively). Averaged across harvests, orchardgrass persisted better in loblolly pine alleys (72% stand) than in the control (44% stand) while tall fescue persisted better in the control (30% stand) than in loblolly pine (13% stand). Persistence in shortleaf pine alleys was intermediate for both herbage treatments. Yields of orchardgrass and the binary mixture did not differ in pine alleys (1300 kg ha−1) and were usually greater than tall fescue yields (≤700 kg ha−1). Crude protein was higher in loblolly pine alleys (172 g kg−1) than in the control (141 g kg−1). Gas exchange parameters were similar for tall fescue and orchardgrass across a range of volumetric soil moisture (15–30%), indicating little difference in drought response. Producers should consider using orchardgrass monocultures or binary mixtures with tall fescue for pine alleys in the midsouth USA.
Placement of UAN for Dryland Winter Wheat in the Central High Plains
Authors: Schlegel A. J. , Dhuyvetter K. C. , Havlin J. L.
Published: July 2010

Research was initiated in 1993 to determine the N fertilizer requirement for dryland winter wheat (Triticum aestivum L.) grown under reduced tillage systems in western Kansas. Six sites in west‐central Kansas were selected each year for 4 yr in cooperation with area farmers. The typical cropping system was wheat‐fallow with reduced tillage practices. All sites were on silt loam soil that ranged in residual soil nitrate‐N content from 2 to 9 mg kg−1 (0‐ to 60‐cm sample). Crop residue cover at wheat planting averaged 28%. Fluid N (28% N as urea‐ammonium nitrate solution, UAN) was injected in the fall and spring and surface broadcast during the winter and spring at five rates (22, 45, 67, 90, and 112 kg ha−1) along with a zero N control. Typical production practices consisted of planting winter wheat in mid‐September with a hoe‐type drill. Grain protein increased linearly with increased N rates with greater than 130 g kg−1 when 112 kg N ha−1 was injected. Apparent fertilizer N recovery decreased with increased N rates, but was consistently higher with fall or spring injected rather than winter or spring broadcast UAN. The straw/yield ratio was greater than 2 across all N rates, which is greater than the commonly used value of 1.7. The soil N test was an indicator of yield response to N fertilization. Grain yields increased in 10 of 13 site‐years with N fertilizer. Average grain yields were 8% greater from spring injected than broadcast UAN. The time of N application had little effect on grain yield. Economic analysis indicated that injecting UAN in the fall or spring was more profitable than topdressing UAN in the winter or spring because of improved yields and/or lower total N costs. These data suggest that N rate recommendations should vary with application method.
Sugarbeet Growth as Affected by Wheat Residues and Nitrogen Fertilization
Authors: Moraghan John T. , Sims Albert L. , Smith Larry J.
Published: July 2010

Little is known about how low‐N, mature wheat (Triticum aestivum L.) straw and high‐N, postharvest volunteer wheat growth from the previous year influence N fertilizer requirements for sugarbeet (Beta vulgaris L.). This 2‐yr field study examined how wheat straw (3.36 and 6.72 Mg ha−1; 3.5 g N kg−1 in 2000 and 8.0 g N kg−1 in 2001), preflowering wheat residues (2.1 to 4.2 Mg ha−1; 29.1 to 44.7 g N kg−1), and urea (0 to 225 kg N ha−1), fall‐applied and incorporated, affected sugarbeet growth. The previous crop was wheat, and wheat straw was removed from the experimental sites subsequent to the grain harvest. Sugar yields were decreased 10% by application of 3.36 Mg ha−1 straw and 25% by 6.72 Mg ha−1 straw in 2000. The corresponding 2001 sugar decreases were 13 and 19%, respectively. Application of 45 kg ha−1 urea N largely overcame the detrimental effect from 3.36 Mg ha−1 straw but only partially overcame the detrimental effect from 6.72 Mg ha−1 straw in both experiments. Plant N, petiole NO3–N, and soil inorganic N (NH4–N + NO3–N) data all indicated that incorporation of low‐N mature wheat straw decreased availability of soil N, probably due to net N immobilization associated with straw decomposition. In contrast to mature wheat straw, application and incorporation of high‐N, preflowering wheat residues increased recoverable sugar yields in both years. Removal of straw after a wheat crop reduces the N fertilizer requirement for a subsequent sugarbeet crop.
Greenhouse Evaluation of Phosphorus Sources Produced from a Low‐Reactive Brazilian Phosphate Rock
Authors: Prochnow L. I. , Chien S. H. , Carmona G. , Henao J.
Published: July 2010

The Patos de Minas phosphate rock (PR) in Brazil is not suitable for direct application due to its low reactivity or for commercial production of P fertilizers because of its high Fe‐Al content. The objective of this study was to investigate the potential agronomic effectiveness of P sources with low water solubility produced from the PR. The P treatments were (i) compacted granular Patos PR with a single superphosphate (SSP) containing high water‐soluble P content at a P ratio of 50:50, (ii) powdered low‐grade single superphosphate (LG SSP) produced from Patos PR with low water solubility, (iii) powdered Patos PR, (iv) powdered mixture of PR and SSP at 50:50 P ratio, and (v) compacted granular SSP. The P sources were incorporated into an acid soil with pH 5.3 at 0, 10, 25, 50, and 100 mg P kg−1 to grow wheat (Triticum aestivum L.) and ryegrass (Lolium perenne L.) as test crops in a greenhouse study. We confirmed that Patos PR was low in agronomic effectiveness, only 1 and 30% as effective as SSP in producing dry matter yield of wheat and ryegrass, respectively. There were no significant differences between LG SSP or compacted PR+SSP [PR+SSP(C)] and SSP in dry matter yields of both crops, whereas mixed PR+SSP was less effective than PR+SSP(C) compared with granular SSP. Compacted PR+SSP and LG SSP can be potential P sources to be produced from the low‐grade PR that could not be used either for direct application or acidulated P fertilizers.
Penetration of Photosynthetically Active and Ultraviolet Radiation into Alfalfa and Tall Fescue Canopies
Authors: Shulski Martha D. , Walter‐Shea Elizabeth A. , Hubbard Kenneth G. , Yuen Gary Y. , Horst Garald
Published: July 2010

Ultraviolet‐B radiation (UV‐B, 280–320 nm) reaching the earth’s surface has deleterious effects on plants. The degree of susceptibility to UV‐B is dependent on the amount of energy present in longer wavelengths of ultraviolet‐A radiation (UV‐A, 320–400 nm) and photosynthetically active radiation (PAR, 400–700 nm). This study was conducted to quantify the UV and PAR light environment and describe the UV‐B/UV‐A and UV‐B/PAR ratios above and below developing vegetative canopies. Transmitted irradiant flux densities of UV‐B, UV‐A, and PAR in a developing alfalfa (Medicago sativa L.) canopy and a tall fescue (Festuca arundinacea Schreb.) canopy were measured at varying solar zenith angles under clear and overcast sky conditions. Extinction coefficients for average transmittance differed for alfalfa and tall fescue; a single equation for each waveband and canopy/sky condition sufficed to describe the average transmittance. Canopy structure, LAI, and, to a lesser degree, the extent of direct and diffuse radiant energy were found to influence penetration more than sun angle. An envelope of transmittances defined by equations representing the maximum and minimum light transmittance illustrates the variability in transmittances and was broadest under clear skies and narrowed with decreasing wavelength. Leaf area altered the average ratios of above‐canopy UV‐B/UV‐A and UV‐B/PAR ratios. The average ratios of above‐canopy UV‐B/UV‐A and UV‐B/PAR ratios varied slightly with year and sky condition. Differences between the two canopies indicate the need to consider canopy architecture in determining the amount of light penetrating a canopy in the UV‐B, UV‐A, and PAR.
Influence of Residual Nitrogen and Tillage on White Lupin
Authors: Wiatrak P. J. , Wright D. L. , Marois J. J.
Published: July 2010

White lupin (Lupinus albus L.) yield and forage quality depend on the tillage and residual N from a previous crop. The objective of this study was to evaluate the response of winter white lupin seeded in two tillage systems [strip‐till (ST) and conventional (CT)] to four N rates applied to a previous cotton (Gossypium hirsutum L.) crop (0, 67, 134, and 202 kg ha−1). The experiment was conducted in 1995–1996 and 1996–1997 growing seasons. The influence of residual N from a previous cotton crop on white lupin dry matter and grain yields, and silage N concentration varied from year to year. Residual N did not influence silage in vitro organic matter digestion (IVOMD), neutral detergent fiber on a dry matter (DM) basis (NDFt), or neutral detergent fiber ash‐free (NDFaf). However, the weight of 1000 lupin seeds increased by 0.07 g for every 1 kg N applied to a previous cotton crop. Dry matter and grain lupin yields were 15 and 31% greater from ST than CT, respectively. Silage NDFt and NDFaf from ST were 6% greater than that from the CT system. However, the IVOMD, N, and P concentrations were 2, 11, and 27% greater from CT than ST, respectively. The results of this study indicate that greater dry matter and grain yields, NDFt, and NDFaf, and lesser IVOMD, N, and P concentration may be obtained from ST than CT. However, the influence of residual N on dry matter and grain yields of white lupin needs to be further defined.
ESTIMATION OF DURATION INDICES FOR REPEATED TENSIOMETER READINGS
Authors: Meek David W. , Singer Jeremy W.
Published: July 2010

Regression analysis of repeated‐measures data from plots in large experiments is both labor intensive and time consuming. When duration estimates characterizing each individual repeated‐measures series are of interest, numerical integrations are possible alternatives. This note evaluates a trapezoidal rule for estimating a wetness duration index that is derived from repeated tensiometer readings of matric potential associated with plots in a recent soybean [Glycine max (L.) Merr.] study. Tensiometer repeated‐measures series were randomly selected from four of the treatments with their replications for a total of 15 plots (of 420 total) associated with a 2‐yr experiment. Regression‐based duration estimates were developed and compared with those derived using an unequally spaced trapezoidal rule. Equivalence between the two estimators was assessed based on multiple statistical analyses. The estimators were virtually identical by all criteria. The numerical method is faster and easier to employ. Furthermore, the concept can be applied to other repeated measurements, and the results may be useful as covariates in other analyses.
Efficient Water Use in Dryland Cropping Systems in the Great Plains
Authors: Nielsen David C. , Unger Paul W. , Miller Perry R.
Published: July 2010

Successful dryland crop production in the semiarid Great Plains of North America must make efficient use of precipitation that is often limited and erratic in spatial and temporal distribution. The purpose of this paper is to review research on water use efficiency and precipitation use efficiency (PUE) as affected by cropping system and management in the Great Plains. Water use efficiency and PUE increase with residue management practices that increase precipitation storage efficiency, soil surface alterations that reduce runoff, cropping sequences that minimize fallow periods, and use of appropriate management practices for the selected crop. Precipitation use efficiency on a mass‐produced basis is highest for systems producing forage (14.5 kg ha−1 mm−1) and lowest for rotations with a high frequency of oilseed crops (4.2 kg ha−1 mm−1) or continuous small‐grain production in the southern plains (2.8 kg ha−1 mm−1). Precipitation use efficiency when calculated on a price‐received basis ranges from $1.20 ha−1 mm−1 (for an opportunity‐cropped system with 4 of 5 yr in forage production in the southern plains) to $0.30 ha−1 mm−1 {for a wheat (Triticum aestivum L.)–grain sorghum [Sorghum bicolor (L.) Moench]–fallow system in the southern plains}. Throughout the Great Plains region, PUE decreases with more southern latitudes for rotations of similar makeup of cereals, pulses, oilseeds, and forages. Forage systems in the southern Great Plains appear to be highly efficient when PUE is computed on a price‐received basis. In general across the Great Plains, increasing intensity of cropping increases PUE on both a mass‐produced basis and on a price‐received basis.
Evaluation of Dry Matter Loss, Nutritive Value, and In Situ Dry Matter Disappearance for Wilting Orchardgrass and Bermudagrass Forages Damaged by Simulated Rainfall
Authors: Scarbrough D. A. , Coblentz W. K. , Humphry J. B. , Coffey K. P. , Daniel T. C. , Sauer T. J. , Jennings J. A. , Turner J. E. , Kellogg D. W.
Published: July 2010

Throughout much of the southeastern USA, hay harvest can be complicated by a high probability of rainfall events that may cause damage to the resultant hay crop. The objectives of this study were to investigate the effects of simulated rainfall and two postrainfall drying methods on losses of dry matter (DM) and changes in nutritive value for wilting orchardgrass (Dactylis glomerata L.) and bermudagrass [Cynodon dactylon (L.) Pers.] forages. Orchardgrass was wilted to moisture concentrations of 674 (WET), 153 (IDEAL), and 41 (DRY) g kg−1 and subjected to 0, 12, 25, 38, 51, 64, or 76 mm of simulated rainfall from a custom‐built rainfall simulator. For IDEAL orchardgrass, DM loss reached a maximum of 88 g kg−1 when 76 mm of simulated rainfall was applied. Dry matter loss, total N, and all fiber components except hemicellulose increased with rainfall amount, exhibiting single or multiple polynomial effects (P ≤ 0.048) in each case; however, responses were not consistent across these response variables. A second study was conducted with bermudagrass using similar techniques, except that the forage contained 761 (WET), 400 (MID), and 130 (IDEAL) g kg−1 of moisture when simulated rainfall was applied. For IDEAL bermudagrass forage, DM losses increased in linear (P = 0.001) and quadratic (P = 0.003) relationships with simulated rainfall, but the maximum DM loss was only 21 g kg−1. For both forages, DM loss and deleterious changes in nutritive value generally increased with rainfall amount, but these responses appeared to be much greater for orchardgrass.
A Comparison of Several Methods for Evaluating the Potassium Status of Some Mississippi Soils
Authors: Nelson L. E.
Published: July 2010

Potassium was extracted from soils by growing five sunflower plants (Helianthus annuus L. Var. Mammoth Russian) in 500 g. of soil in the greenhouse for 10 weeks. Adequate fertility was provided by adding periodically in small aliquots 1,400 ml. of a nutrient solution complete except for K. In preliminary experiments the effects of length of cropping period, addition of fertilizer K, and day length and temperature were studied.

Seventeen representative Mississippi soils were obtained, and total K removal by sunflower was compared to removal by various chemical methods. Chemical methods compared were exchangeable K by N NH4OAc, 0.5N NH4Cl in 0.25N HCl and 0.5N HCl for 15 minutes, and K released by boiling N NHO3, heating to 500° C., and continuous percolation with distilled water. The best correlations were obtained with those methods measuring exchangeable K.

In another experiment correlation coefficients between K extracted by sunflower and exchangeable K by N NH4OAc for 29 surface soils and 22 subsoils were 0.899 and 0.928, respectively. The same correlation for upland surface soils was 0.977; for terrace and bottom surface soils, 0.929.

A Kaufman sandy loam, continuously fertilized for 30 years with a complete fertilizer was found to accumulate both exchangeable and nonexchangeable K. The uptake of K by sunflower correlated equally well with K extracted by N NH4OAc or boiling N HNO3.
Maintaining High Soil Nutrient Levels for Greenhouse Tomatoes Without Excess Salt Accumulation
Authors: Lucas R. E. , Wittwer S. H. , Teubner F. G.
Published: July 2010

Experimental and commercial plantings of greenhouse tomatoes received supplemental fertilizers in the form of KH2PO4, (NH4)2HPO4, KNO3 and NH4NO3 in quantities greater than normally applied. Monthly changes in soil nutrient levels and soluble salt contents were determined and crop behavior observed. A total of 2,922 pounds of nitrogen, 3,054 pounds of P2O5, and 4,662 pounds of K2O per acre were applied during two growing seasons in experimental plantings at the Michigan State University. Soil tests near the end of the growing season for the second year showed 10 pounds of nitrate‐N, 188 pounds of P, and 402 pounds of K per acre by the Spurway “active” method. The soluble salt reading for a 1:2 soil/water mixture was 28 × 10‐5 mho. Yields up to 100 tons of fruit per acre were harvested resulting in total crop removal of 350, 105, and 580 pounds per acre of nitrogen, phosphorus, and potassium, respectively. Cooperative studies were conducted with seven commercial growers. The fertilizer program followed closely that used at the University. Results of soil tests and soluble salt readings were similar to those obtained at the University greenhouse.
Prediction of Evaporation from Homogeneous Soil Based on the Flow Equation
Authors: Gardner H. R.
Published: July 2010

Evaporation of water from columns packed with McGrew loamy sand was measured for three different sequences of six water additions and evaporation times totaling 60 days. These treatments were: (1) equal amounts of water added and equal times evaporated, (2) equal amounts applied and varied evaporation times, and (3) various amounts applied and equal evaporation times. The average times and amounts were the same in all treatments, and the total losses were approximately the same. A solution for the diffusivity equation for soils of finite depth was used to predict the cumulative water loss for all the treatments event by event and by an averaging technique. The predicted amounts were all within 6.5% of the total cumulative evaporation.
Estimate of Organic Carbon in World Soils: II
Authors: Bohn Hinrich L.
Published: July 2010

Soil organic carbon (C) is the largest carbon reservoir at the earth's surface, but its mass is the least certain. The completed FAO Soil Map of the World yielded these estimates: 22 × 1014 kg organic C in global soils, made up of 18 × 1014 kg C in mineral soils and 4 × 1014 kg C in the surface meter of peatlands.
Analysis of Long‐Term Water Table Depth Records from a Hydrosequence of Soils in Central Ohio
Authors: Zobeck T. M. , Ritchie A.
Published: July 2010

Water table depths and precipitation were measured over a 10‐yr period on four adjacent forested soils in central Ohio. The soils included a hydrosequence of well, moderately well, poorly, and very poorly drained fine‐textured soils. Graphs describing the probability of observing water tables during consecutive 2‐week (semi‐monthly) intervals, by soil depth class, were compared with estimates reported on USDA‐Soil Conservation Service forms SOIL‐SOI‐5 and a method proposed in the Soil Survey Manual. All soils had a probability of an observed water table within 50 cm of the soil surface. Water tables were observed in all soils, with the exception of the well drained soil, within 25 cm of the surface, 10% of the time or more, over a 12‐ or 14‐week period in the late winter and spring.
Single Empirical Relationship for Potassium Exchange Equilibria in Various Soils
Authors: Dufey Joseph E. , Marot Jean M.
Published: July 2010

The exchange behavior of K ions was studied in a collection of 40 soil samples from southern Belgium. These soils are characterized by wide differences of mineralogical composition, cation exchange capacity (CEC), and base saturation percentage. The prevailing basic cations on the exchange complexes are Ca, Mg, and K; Na is negligible. The Gapon formalism (i.e., exchangeable K ratio, EKR, vs. K adsorption ratio, KAR) is used to describe the relationship between the K concentrations in the surface and solution (water extract at 1:3 soil/H2O ratio) phases. When EKR is expressed (as it is usual) as [K]i/([Ca]i + [Mg]i)‐[ ]i refers to surface concentrations, molckg−1—the dispersion of the experimental points around the line EKR vs. KAR is very high. However if EKR is expressed as [K]i/(CEC − [K]i), a fair linear relationship with low statistical dispersion is observed. This relationship shows that the exchange equilibria of K in our soils cannot be simply regarded as a K vs. (Ca + Mg) exchange reaction. This is likely related to the fact that in most samples the sum of exchangeable bases was lower than the CEC. Such a single relationship, though difficult to explain, may be especially useful for modeling purpose.
Solubility Characteristics of Residual Phosphate in a Fertilized and Limed Ultisol
Authors: Harrison Robert B. , Adams Fred
Published: July 2010

Except at very low P rates, residual soil P (i.e., that measured by most extraction methods) continues to increase with annual additions of P fertilizer. Phosphorus retention mechanisms, however, are still much debated and difficult to prove or disprove. In an effort to determine whether the solubility of phosphate minerals controlled soil‐solution P concentration in the field under some conditions, samples from the Ap of a Benndale sandy loam (Typic Paleudults) were collected from plots of a field experiment with different pH and P levels and analyzed in the laboratory. Several soil pH levels were first established (5.0–8.0); this was followed by annual additions for 7 yr of concentrated superphosphate at five rates varying from 0 to 392 kg P ha−1 yr−1 and cropping annually. Soil‐solution composition was determined on samples taken 1, 3, and 5 yr after discontinuing P fertilization. Except for the “no P” treatment, solution P increased with increasing pH up to pH 5.8, then it decreased as pH increased, suggesting the accumulation of a basic phosphate mineral such as hydroxyapatite at about pH 5.8 and above. However, this was not matched by the ion activity product (IAP) for Ca5OH(PO4)3 or any other P mineral. For instance, at each P level, pCa5OH(PO4)3 decreased almost linearly with increasing pH so that each P level had one and only one pH at which pCa5OH(PO4)3 equalled 57.5, the accepted solubility product for hydroxyapatite. Thus, IAP's could not be used to predict, even indirectly, that solid‐phase minerals were or were not controlling solution P. Sequential equilibration of selected soil samples with 0.01 M MgCl2, however, provided data that strongly supports the hypothesis that hydroxyapatite was present in a “high P, high pH” soil but not in a “low P, high pH” or a “high P, low pH” soil.