bluuebunny/crossref_metadata_2025 huggingface dataset:
Evapotranspiration and Yield of Corn Grown on Three High Plains Soils
Authors: Tolk Judy A. , Howell Terry A. , Evett Steven R.
Published: July 2010

Soil properties that vary within a production area present management challenges to producers when water supplies are limited. We conducted three experiments to determine the influence of soil type and different water management levels on corn (Zea mays L.) yield, evapotranspiration (ET), and water use efficiency. Short‐season corn was grown at low population density in Iysimeters containing monolithic soil cores of Pullman (fine, mixed, superactive, thermic Torrertic Paleustoll), Ulysses (fine‐silty, mixed, superactive, mesic Aridic Haplustoll), and Amarillo (fine‐loamy, mixed, thermic Aridic Paleustalf) soils, at a rain shelter facility in Bushland, TX. Dryland conditions were simulated in 1994 and 1995, with the soils receiving irrigations totaling either 50 or 150 mm in 1994 and either 120 or 200 mm in 1995. In 1996, water management levels were expanded, with the soils receiving weekly irrigation equivalent to 20, 50, 80, and 110% of measured ET. Grain yields for the 3 yr ranged from 389 to 804 g m−2 for the Pullman soil, 559 to 899 g m−2 for the Ulysses soil, and 438 to 736 g m−2 for the Amarillo soil. Low grain yields from corn in the Pullman soil were due to limited water extraction from the lower soil profile. Even under full irrigation (110%), grain yield and leaf area were lower for corn in the Amarillo soil than with the two other soils, possibly due to limited water availability. Soil type effects on corn water use and yield may require different water management strategies for optimum water use efficiency.
Manure, Tillage, and Crop Rotation: Effects on Residual Weed Interference in Spring Barley Cropping Systems
Authors: Stevenson F. Craig , Légère Anne , Simard Régis R. , Angers Denis A. , Pageau Denis , Lafond Jean
Published: July 2010

Effects of management practices on crop growth and yields may or may not be mediated through crop‐weed interactions. Our objective was to detect and confirm a relationship between the influence of crop management factors on spring barley (Hordeum vulgare L.) and the potential occurrence of crop‐weed interference. A field study was established on a Normandin clay (fine, mixed, frigid Humic Cryaquept) at Normandin in Québec to investigate the effects of crop rotation, tillage (chisel plow, CP; moldboard plow, MP), and nutrient source on midseason aboveground dry weight and seed yield of barley and residual weed populations. Barley‐weed interference was detected using ANOVA, principal components analysis, and analysis of covariance. A reduction in midseason dry weight (36%) and seed yield (59%) of barley in the CP relative to the MP treatment in 1994 was associated with interference from broadleaf plantain (Plantago major L.) and dandelion (Taraxacum officinale Weber in Wiggers). A 20% reduction in midseason dry weight and seed yield with CP tillage in 1995 was associated with interference from volunteer timothy (Phleum pratense L.) and Kentucky bluegrass (Poa pratensis L.). Barley dry weight and seed yield were 29 and 26% greater in the barley‐forage rotation compared with the monoculture in all years except 1995, despite greater weed pressure in the barley‐forage rotation, confirming the benefits of forages to subsequent crops in a rotation. Compared with mineral fertilizer, application of manure resulted in lower dry weight and seed yield for barley; however, this reduction was not associated with weed interference. In contrast to tillage, crop rotation and nutrient source effects on crop variables appeared mediated through factors other than weed interference.
Dry Matter and Nitrogen Accumulation in Rice Inoculated with a Nitrogenase‐Derepressed Mutant of Anabaena variabilis
Authors: Kamuru Freeman , Albrecht Stephan L. , Allen Leon H. , Shanmugam K. T.
Published: July 2010

Cyanobacteria contribute to the N economy of flooded rice (Oryza sativa L.) fields by reducing N2 to NH3. The purpose was to determine the extent to which a nitrogenase‐derepressed mutant strain of the cyanobacterium Anabaena variabilis (strain SA‐1), capable of excreting newly fixed N as NH3, could provide N for rice plants grown outdoors in pots. Growth of plants inoculated with the mutant strain was compared with growth of plants inoculated with the parent strain (A. variabilis, strain SA‐0) or fertilized with inorganic N fertilizer [(NH4)2SO4] at rates of 0 (control), 25, 50, and 100 kg N ha−1. Rice plants inoculated with the mutant cyanobacterium produced more panicles than plants inoculated with the parent strain. Dry matter and total N contents of the root, shoot, and grain were significantly greater (P < 0.05) in the plants inoculated with the NH3‐excreting mutant strain than plants that were inoculated with the parent strain of the cyanobacterium. Under these conditions, the contribution of the mutant cyanobacterium to growth and yield of rice plants was equivalent to the application of 71 to 73 kg N ha−1 as (NH4)2SO4. Estimates of the rate of N2‐fixation (acetylene reduction) in pots inoculated with the NH3‐excreting mutant cyanobacterium were about twice the amount observed in pots inoculated with the wild‐type strain, even in the presence of (NH4)2SO4. Pots inoculated with the mutant strain also had more NH3 in the flood water than pots that were inoculated with the parent strain. The NH3‐excreting strain of A. variabilis shows potential for development for use as a biofertilizer in paddy rice production in areas where inorganic fertilizer N is unavailable or expensive and in rice production systems that aim to minimize environmental pollution from inorganic N fertilizers.
Sesbania Tree Fallows on Phosphorus‐Deficient Sites: Maize Yield and Financial Benefit
Authors: Jama Bashir , Buresh Roland J. , Place Frank M.
Published: July 2010

Rotation of Sesbania sesban (L.) Merr., a fast‐growing N2‐fixing tree, with maize (Zea mays L.) has potential for increasing fertility of tropical soils, where fertilizer use by resource‐poor farmers is limited. At two sites in Kenya (Ochinga, with a Kandiudalfic Eutrudox soil, and Muange, with a Kandic Paleustalf), we compared maize yields and financial returns for (i) sesbania grown for three or four seasons followed by three maize crops (sesbania fallow), (ii) one maize crop followed by natural regrowth of vegetation for three seasons and then three maize crops (natural fallow), and (iii) maize monoculture for seven seasons. After the fallows, plots were split with and without added P. Maize responded to P at both sites. Cumulative grain yields for seven seasons of maize monoculture were 8.4 Mg ha−1 at Ochinga and 5.6 Mg ha−1 at Muange. They were comparable to cumulative maize yields for sesbania fallow (Ochinga, 10.6 Mg ha−1 Muange, 4.5 Mg ha−1) and natural fallow (Ochinga, 7.7 Mg ha−1; Muange, 4.2 Mg ha−1), even though maize was grown for only three or four seasons in the fallow treatments. Sesbania fallow was financially attractive at Ochinga (≥500 mm rain in each season) but not at Muange, where low rainfall (<300 mm in each postfallow season) limited maize yield. Phosphorus fertilization of maize at Ochinga increased (P < 0.2) net benefit for sesbania fallow. Improved fallows have potential to supply nutrients to crops, but they are unlikely to eliminate the need for P fertilizers on P‐deficient soils.
Does Variable Rate Seeding of Corn Pay?
Authors: Bullock Donald G. , Bullock David S. , Nafziger Emerson D. , Doerge Thomas A. , Paszkiewicz Steven R. , Carter Paul R. , Peterson Todd A.
Published: July 2010

Not all fields, nor even portions of fields, have the same economically optimal corn plant density. However, until the recent introduction of precision farming, producers could not benefit from these accepted intrafield differences. This field study was conducted on 170 cooperating farmer fields throughout the Midwestern U.S. Corn Belt between 1987 and 1996 and consisted of over 42 000 individual experimental units. At each location, corn (Zea mays L.) was overplanted and thinned to 44 000 to 104 000 plants ha−1. The objective of our field research was to estimate the economic value, to the farmer, of variable rate seeding (VRS) as compared with uniform rate seeding (URS). We first estimated the correlation between field quality and economically optimal plant density. The economically optimal uniform plant density for the Midwest Corn Belt was 67 900 plants ha−1. For every tonne per hectare increase in site quality, as measured by yield potential, the predicted value of the site‐specific economically optimal plant density increased by approximately 1200 plants ha−1. We compared differences in revenues minus seed costs on four simulated fields. The value of VRS, ignoring the costs of VRS equipment and services, ranged from $12.83 ha−1 for farmers with VRS technology and full information to $0.15 ha−1 for farmers with VRS technology but only partial information. Profitable implementation of VRS will require detailed and expensive information regarding site characteristics, production inputs, and stochastic factors. Therefore, VRS will remain economically infeasible for most commercial corn growers until the cost of obtaining such information decreases considerably.
Path Analyses of the Yield Formation Process for Late‐Planted Soybean
Authors: Board James E. , Kang Manjit S. , Harville Bobby G.
Published: July 2010

Strategies to increase yield of late‐planted soybean [Glycine max (L.) Merr.] in the southeastern USA would be improved by an understanding of how yield components interact with one another in affecting yield at both the phenotypic and genotypic levels. Our objective was to apply path analyses to data collected from previous studies to determine the relative importance of yield components in the overall yield formation process when environmental and genotypic factors were varied. Path analyses were applied within primary yield components (the predictor variables seed number and seed size, affecting the response variable yield), secondary yield components (the predictor variables pod number and seed per pod, affecting the response variable seed number), and tertiary yield components (the predictor variables pods per reproductive node, reproductive node number, percent nodes becoming reproductive, and node number, affecting the response variable pod number). Path analyses were applied to three data sets constructed from field studies conducted from 1987 to 1993 near Baton Rouge, LA (30° N lat). Phenotypic analyses, which involved altered source strength (canopy assimilatory capacity as indicated by crop growth rate or light interception) during the reproductive period (R1 to R7), affected yield through adjustments in pods per reproductive node and reproductive node number. Pods per reproductive node was also the most important yield component influencing pod and seed number on the genotypic level, although negative compensation between seed number and seed size (at the genotypic level only) precluded a positive effect on yield.
Remobilization of Pre‐Anthesis Assimilates to the Grain for Grain Only and Dual‐Purpose (Forage and Grain) Triticale
Authors: Royo Conxita , Voltas Jordi , Romagosa Ignacio
Published: July 2010

In Mediterranean environments, translocation of pre‐anthesis assimilates to the grain is an important source of photosynthates. In this work, the effect of forage removal at the beginning of jointing on the amount of dry matter (DM) accumulated before anthesis and remobilized during grain filling was studied in five spring and five winter triticale genotypes (×Triticosecale Wittmack). Field experiments were conducted in 1992 and 1993 in northeastern Spain. Two harvesting treatments were used: (i) grain production only and (ii) cutting the crop for forage at the beginning of jointing and harvesting the grain produced after regrowth. Pre‐anthesis storage of carbohydrates was very important to grain filling in triticale, both for grain and for dual‐purpose. Contribution of pre‐anthesis assimilates to grain yield in the uncut plots was 46% in spring triticale genotypes and 65% in winter genotypes, as the later‐maturity winter triticale genotypes were more affected by terminal abiotic stresses. Reductions in DM accumulated at anthesis after forage removal were more pronounced in winter genotypes (39%) than in spring genotypes (20%), where an earlier development allowed for a longer recovery period after cutting; DM reductions were similar to grain yield decreases. The effect of forage removal on translocation depended on the growth hbit of the genotype and environmental conditions. Most differences were associated with changes in crop phenology. In spring types, with early jointing, DM translocation and the contribution of pre‐anthesis assimilates to grain were not affected by forage removal, whereas both traits were drastically reduced in winter triticale. Most differences in 13C/12C carbon isotope discrimination (Δ) in grains were also phenology driven.
Switchgrass Seedling Development as Affected by Seed Size
Authors: Smart Alexander J. , Moser Lowell E.
Published: July 2010

Seed size has been associated with early seedling vigor (i.e., germination rate, emergence rate, and growth) in grasses. This study was conducted to compare seedling development over a 60‐d period in the field as affected by heavy seed (HS) (0.19 to 0.21 g 100 seed−1) and light seed (LS) (0.13 to 0.16 g 100 seed−1) of ‘Blackwell’ and ‘Trailblazer’ switchgrass (Panicum virgatum L.). The experiment was conducted in 1995 and 1996 at Lincoln, NE, on a Kennebec silt loam (fine‐silty, mixed, superactive, mesic Cumulic Hapludolls). The experimental design was a randomized complete block with four replicates. Seed was separated into two sizes using a South Dakota seed blower. Seed was planted into rows at a rate of 100 pure live seed per meter of row. Plants were excavated and evaluated for shoot weight, leaf area, and root weight. Shoot and root systems were morphologically staged four times during the summer. Seed size differences in switchgrass appeared to produce only slight differences in morphological development of shoot and root systems, leaf area, shoot weight, and adventitious root weight from seedling emergence to 6 wk of growth. Adventitious roots formed more quickly on seedlings from heavier than lighter seed, but the advantage to seedling establishment was minimal even when soil moisture appeared to be lacking. By 8 to 10 wk after emergence, growth and development of LS seedlings were similar to HS seedlings. Once seedlings formed two or more adventitious roots, seed size no longer affected establishment and growth. Seed size in switchgrass appears to have a minimal long‐term effect on growth and development of seedlings.
Chicory Effects on Lamb Weight Gain and Rate of In Vitro Organic Matter and Fiber Disappearance
Authors: Turner Kenneth E. , Belesky David P. , Fedders James M.
Published: July 2010

In modern forage systems, there is increased emphasis on use of nontraditional forages to supply nutrients to livestock. Field and laboratory experiments were conducted to evaluate the utility and nutritive value of chicory (Cichorium intybus L.; CHIC) as a component of hill‐land pastures in Appalachia. In 1995, lamb (Ovis aries) gain was 56.1 kg ha−1 on orchardgrass (Dactylis glomerata L.; OG), while those grazing OG + CHIC lost 24.2 kg ha−1 during the 44‐d midsummer grazing period (P < 0.05). In 1996, while weight gains were not different (P > 0.10), total lamb production per hectare was 14% less on OG + CHIC (258 kg ha−1) than on OG only (300 kg ha−1) for the 79‐d grazing period. In 1997, total weight gained for the season was not different (P > 0.10); lambs grazed OG or OG + CHIC for 110 d and production was 362 and 351 kg ha−1, respectively. Laboratory mixtures of 40:60 or 60:40 OG:CHIC had higher (P < 0.05) in vitro organic matter disappearance (IVOMD), compared with 100% OG or 100% CHIC. There was a synergism in mixtures with orchardgrass that increased IVOMD relative to pure samples. Another laboratory experiment suggested that as total N increased in chicory herbage, rate of in vitro neutral‐detergent fiber (NDF) disappearance decreased. More information on the influence of soil type and management on chicory growth in pure stands and mixtures with other plant species is needed to optimize productivity of systems that include chicory.
Effects of Mechanical Conditioning on Wilting of Alfalfa and Italian Ryegrass for Ensiling
Authors: Borreani Giorgio , Tabacco Ernesto , Ciotti Angelo
Published: July 2010

Conditioning may greatly increase the drying rate of cut forage during the initial stages of drying. Such results may be particularly useful for silage systems (as opposed to haymaking). This study was conducted to determine the drying rate and losses in six field wilting trials on pure stands of alfalfa (Medicago sativa L.) and Italian rye‐grass (Lolium multiflorum Lam.) when treated with different types of mower‐conditioners (rubber rolls; plastic or steel flails). Drying was measured by calculating the water loss rate from two subsequent hourly weights of swath portions placed on trays. Dry matter (DM) losses were estimated on 1.2‐m lengths of swaths immediately after cutting. The steel flail conditioner provided faster drying than the other conditioning types for both crops. The effect of the rubber roll conditioner was limited due to the swath structure, especially with forage surface densities higher than 0.7 kg DM m−2. Tedding positively interacted with the conditioning treatment to increase the drying rate, especially when forage was conditioned with the rubber roll machine. Shatter losses from alfalfa were higher for the flail conditioner, ranging from 3.6 to 10.2%, and with greater loss of crude protein. The DM losses were always lower than 2.5% for Italian ryegrass. The most severe conditioning (steel flails) followed by tedding is appropriate for grass, as it significantly reduces the wilting time without affecting DM loss. However, a less severe conditioning (rubber rolls) without tedding is more appropriate for wilting alfalfa, to avoid excessive leaf and protein loss.
Demography of Wild Oat in Barley Crops: Effect of Crop, Sowing Rate, and Herbicide Treatment
Authors: Scursoni Julio , Benech‐Arnold Roberto , Hirchoren Hernán
Published: July 2010

Wild oat (Avena fatua L.) is a major weed in barley (Hordeum vulgare L.) in Argentina. During 1993, 1994, 1995, and 1996, demographic studies of wild oat in barley crops were conducted to assess the effect of herbicide treatment, crop, and sowing rate on the demographic processes of seedling establishment, survival rate, reproductive performance, preharvest seed dispersal rate, and fate of seed in the soil during the fallow period. The herbicide was diclofop‐methyl: methyl 2‐[4‐(2,4‐dichlorophenoxy)phenoxy]propanoic acid. Increasing barley sowing rate from 160 plants m−2 to 280 plants m−2 effectively reduced the amount of wild oat seeds that entered the soil seed bank by 50% through lowering fecundity. Diclofop‐methyl reduced the number of seeds that entered the soil seed bank sevenfold (1050 vs. 140 seeds m−2) through a reduction in both seedling survivor rate and reproductive output. In addition, the diclofop‐methyl treatment delayed the onset of seed maturity and reduced the dormancy level of the seeds produced by the surviving plants. Half the number of wild oat seeds entered the seed bank in a barley than in a wheat (Triticum aestivum L.) crop. This was through a lower wild oat reproductive output and a higher rate of seed dispersal related to the later harvest time of wheat relative to barley. These data indicate that integrated control of wild oat should include herbicide treatment, crop selection, and sowing rate.
Sunflower Response to Tillage and Nitrogen Fertilization under Intensive Cropping in a Wheat Rotation
Authors: Halvorson Ardell D. , Black Alfred L. , Krupinsky Joseph M. , Merrill Stephen D. , Tanaka Donald L.
Published: July 2010

Sunflower (Helianthus annuus L.) is a warm‐season, intermediate water‐use crop that can add diversity to dryland crop rotations. Reduced tillage systems may enhance sunflower yield in intensive cropping systems. A 12‐year study was conducted to determine how sunflower cultivars of early and medium maturity respond to tillage system (conventional‐till, CT; minimum‐till, MT; no‐till, NT) and N fertilization (34, 67, and 101 kg N ha−1) within a dryland spring wheat (Triticum aestivum L.)–winter wheat–sunflower rotation. Averaged across N rates, cultivars, and years, sunflower seed yields were greater with MT (1550 kg ha−1) than with NT (1460 kg ha−1) and CT (1450 kg ha−1). Increasing N rate above 34 kg N ha−1 generally increased grain yield, but varied from year to year. The tillage × N interaction showed that the highest seed yields were obtained with NT (1638 kg ha−1) and MT (1614 kg ha−1) at 101 kg N ha−1. Total plant‐available water (TPAW) of <350 mm greatly reduced sunflower yield potential, due to water stress, compared with yields for 350 to 500 mm of TPAW. TPAW > 500 mm did not result in increased sunflower yields over those with 350 to 500 mm TPAW. Yield differences between cultivar maturity classes varied from year to year and with tillage and N level. At the lowest N rate, weeds were more problematic in NT than in CT and MT plots. More N fertilizer may be needed with NT to optimize sunflower yields than with CT and MT, because of less residual soil NO3–N with NT. Results indicate that producers in the northern Great Plains can use sunflower successfully in annual cropping systems, particularly if MT and NT are used with adequate N fertilization.
Comparison of Plant Measurements for Estimating Nitrogen Accumulation and Grain Yield by Flooded Rice
Authors: Ntamatungiro Sixte , Norman Richard J. , McNew Ronald W. , Wells Bobby R.
Published: July 2010

Knowledge about N accumulation during the vegetative growth stage of flooded rice (Oryza sativa L.) may be useful in determining the need for topdressing fertilizer N at panicle differentiation (PD). In a 3‐year field study, plant area, N concentration of the Y‐leaf (most recently matured leaf blade) and the whole plant, and chlorophyll meter (SPAD) readings measured during vegetative and early reproductive growth stages were used to estimate total N accumulation. The techniques were then used to determine the growth stages that maximized correlation with grain yield. Five preflood (PF) N rates (0, 33.6, 67.2, 100.8, and 134.4 kg ha−1), two PD N rates (0 and 67.2 kg ha−1), and two cultivars (LaGrue and Lacassine) were used. The treatments were chosen to represent an array of dry matter and total N accumulations. No interactions of PF N rate × cultivar on grain yield and total N accumulation were observed. Plant area was linearly correlated (r = 0.84 to 0.93, P < 0.05) to dry matter accumulation, and accounted for >60% of the variation in total N accumulation every year. However, Y‐leaf N concentration and SPAD readings accounted for <60% of the variation in total N accumulation in 1993 and 1994, and for >60% only in 1995. A combination of plant area and Y‐leaf N concentration or SPAD readings accounted for more variation in total N accumulation than did individual plant measurements. Plant area and whole‐plant N concentration was the best combination, accounting for 80 to 90% of the variation in total N accumulation. The maximum variation in grain yield accounted for by the measured traits was 50% at PD for plant area, and 37% at 2 wk after the PF N application for Y‐leaf N concentration and SPAD reading. These low correlations of grain yield with plant measurements during the vegetative stage confirm that environmental and other conditions prevailing during later growth stages profoundly influenced grain yield of rice.
Planting Date and Phosphorus Fertilizer Placement Effects on Winter Wheat
Authors: Sander Donald H. , Eghball Bahman
Published: July 2010

Two banding methods of applying P to winter wheat (Triticum aestivum L.), seed and knife (dual placement), have generally performed similarly when averaged over years and locations. However, performance can vary considerably from year to year, or even between locations. This study was conducted to determine the effect of optimal and delayed date of wheat planting on the performance of seed‐applied and knifed P on grain yield, P uptake, and yield components. Four rates of P (0, 11.2, 22.4, and 33.6 kg P ha−1) were seed‐ and knife‐applied on a Sharpsburg soil (fine, smectitic, mesic Typic Argiudoll) and Crete soil (fine, smectitic, mesic Pachic Argiustoll) in 1986 and two Crete soils and one Wymore soil (fine, smectitic, mesic Aquertic Argiudoll) in 1987. There were two planting dates in 1986 and three in 1987. All five soils had soil P test levels of low to very low (Bray and Kurtz P1 of 5 to 7 mg kg−1). While seed and knife application performed similarly with an optimum planting date, seed application was a superior P application method in terms of grain yield and P uptake when planting was delayed. The primary reason for the superiority of seed P application was its ability to stimulate tillering and head formation at the later planting dates. The difference in performance between the two methods of P application was probably related to quicker root access to the fertilizer P in the fall soon after planting. Root access to fertilizer P in the fall influences the number of tillers developed, which determines head number at harvest and final grain yield. Results of this research suggest that, when wheat planting date is delayed, fertilizer P should be applied with the seed for maximum effectiveness.
Increased Dryland Cropping Intensity with No‐Till Barley
Authors: Schillinger William F. , Cook R. James , Papendick Robert I.
Published: July 2010

For most of a century, the wide spread practice of growing only one crop every other year in a tillage‐based wheat (Triticum aestivum L.)–fallow rotation has degraded soils and contributed to environmental problems in low‐precipitation (<350 mm annual) dryland regions of the inland Pacific Northwest of the USA. Many growers in this 2‐million‐ha cropland area are increasing the intensity of cropping with spring crops, but most use conventional tillage (CT) for seedbed preparation. The agronomic performance of spring barley (Hordeum vulgare L.), sown into CT seedbeds with double‐disk drills or into standing stubble with several types of no‐till (NT) drills (hoe, single disk, and notched coulter), was determined in two experiments conducted both in 1996 and 1997 where the previous crop was either winter wheat or spring barley. We measured stand establishment, seed‐zone temperature, soil water, dry biomass accumulation, rhizoctonia root rot, surface residue retention, and grain yield components. Plant stand , dry biomass accumulation , and spike density as single independent variables, and combined in a multiple regression model , were strongly correlated (P < 0.001) to grain yield. Early‐season seed‐zone temperatures were cooler under NT, but seed‐zone water was slightly higher with CT. Low spike density consistently occurred in a wide row spacing (406 mm) NT drill treatment, and the highest overall yields were obtained with NT drills with rows spaced 255 mm or less. Rhizoctonia root rot was severe on seminal roots in all treatments in three out of four trials, but did not appear to limit yields, possibly due to healthy crown roots and favorable growing conditions. No‐till spring sowing into undisturbed standing stubble (2420–5230 kg ha−1) can produce grain yields equal to or exceeding those under CT and can provide environmental and potential soil quality benefits for low‐precipitation dryland farming areas in the inland Pacific Northwest.
Conversion of Conservation Reserve Program (CRP) Grassland for Dryland Crops in a Semiarid Region
Authors: Unger Paul W.
Published: July 2010

Information was needed regarding practices suitable for returning grassland to cropland when Conservation Reserve Program (CRP) contracts expired. A study on Pullman soil (Torrertic Paleustoll) involved seven tillage treatments (no‐tillage and reduced, sweep, disk, moldboard plus disk, burn–sweep, and burn–disk tillage) with vegetation retained and the five non‐burn tillage treatments with vegetation removed before treatment. Fertilizer (NH4NO3) was applied at 0, 34, and 67 kg N ha−1 in 1995 and at 0, 67, and 134 kg N ha−1 in 1996 and 1997. Initial soil water contents were low, and soil never was filled with water at planting time. Sorghum [Sorghum bicolor (L.) Moench] yielded ≤720 kg ha−1 in 1995, and the 1995–1996 wheat (Triticum aestivum L.) crop failed. Sorghum was not planted in 1996 because of a drought. Sorghum yielded 2260 to 4700 kg ha−1 in 1997. Wheat yielded 1410 to 1980 kg ha−1 in 1996–1997. Vegetation retention or removal affected yields slightly. Fertilization affected sorghum yields slightly and increased wheat yields. Vegetation control was difficult with no‐tillage. Disk tillage to dislodge grass, followed by reduced‐ or no‐tillage, appears best for converting CRP grassland to cropland in this semiarid region. Because of low initial soil water contents, a 90‐d period is inadequate for obtaining adequate soil water storage unless precipitation is much above normal. Forgoing planting a crop soon after killing the vegetation when precipitation is low would provide more time for storing soil water and increase the potential for obtaining favorable yields.
Estimating Solar Irradiance for Crop Modeling Using Daily Air Temperature Data
Authors: Goodin Douglas G. , Hutchinson J. M. S. , Vanderlip Richard L. , Knapp M. C.
Published: July 2010

Crop growth models require solar irradiance as input data, yet there are few places where such data are routinely measured. For locations where measured values are not available, solar irradiance can be estimated using empirical models such as the Bristow–Campbell (B–C) model. This study was conducted to assess the spatial and seasonal accuracy of the B–C model for midcontinental locations in Kansas. A 30‐year data set from Manhattan, KS, was used to calibrate and evaluate unmodified and modified forms of the B–C model. The effect of seasonality was investigated by subdividing the yearly data into two subsets, a high noontime solar elevation angle period, ranging from DOY 121 to 273, and a low noontime elevation angle period comprising the remainder of the year. The B–C model was also evaluated without seasonal division of the year. The calibrated models were then tested against measured solar irradiance values for 10 sites distributed across the state of Kansas. Results indicate that, for the calibration site at Manhattan, irradiance was more accurately estimated using a modified form of the B–C model. For the yearly data, root mean square error (RMSE) was 3.9 MJ m−2 d−1 (25% error), compared with 5.2 MJ m−2 d−1 (24% error) for the high solar elevation angle period and 3.6 MJ m−2 d−1 (32% error) for the low solar elevation angle period. The RMSE for the 10 test sites ranged from 2.0 to 6.2 MJ m−2 d−1; percentage error ranged from 26 to 47%. Neither latitude nor distance from the calibration site significantly affected the accuracy of irradiance estimates at the evaluation sites. Results suggest that the modified B–C model provides reasonably accurate estimates of irradiance at noninstrumented sites and that the model can successfully be used at sites away from the calibration site. Seasonal subdivision of the data adds little to the accuracy of estimates.
Contract Hog Production and Environmental Management in the Southern United States
Authors: Welsh Rick , Hubbell Bryan
Published: July 2010

The 1980s and 1990s have witnessed substantial changes in the U.S. swine industry. The industry structure has shifted from relatively large numbers of hog (Sus scrofa) farm operators producing for open markets to fewer and larger farm operators raising hogs under contracts for intermediary firms or meatpackers. This shift has resulted in debates over whether the movement from independent to contract hog production has proven beneficial or detrimental for manure management and pollution control. To shed light on these debates, we surveyed by mail independent and contract hog producers in the southern USA and gathered data on the structure of their farms, their opinions on environmental issues in the hog industry, and their manure management strategies. The survey results indicate that contract producers maintain higher animal units per hectare and spread the hog manure over smaller areas than do independents. However, contract producers also realize they are pushing the adsorptive capacity of their farms and adopt ameliorating and monitoring technologies at higher rates than independent producers. We conclude that market structure is an important determinant of farm structure and environmental management regime, and that adoption of pollution control technologies is not equivalent to environmental performance.
Grass Species and Cultivar Effects on Establishment of Grass–White Clover Mixtures
Authors: Sanderson Matt A. , Elwinger Gerald F.
Published: July 2010

Grasses may differ in their compatibility with white clover (Trifolium repens L.) during establishment. We conducted greenhouse and field experiments to evaluate the compatibility of early‐ and late‐maturing cultivars of perennial ryegrass (Lolium perenne L.) and orchardgrass (Dactylis glomerata L.) with ‘Will’ white clover during establishment. Monocultures and binary mixtures of each cultivar with white clover were established from seed in pots in two greenhouse studies. After an initial harvest at 6 wk of growth, plants were harvested every 2 or 4 wk at a 4‐ or 8‐cm height for 8 wk. The same monocultures and mixtures were planted in field plots and harvested twice at 4 or 8 cm after an 11‐wk establishment period. White clover produced more (P < 0.05) stolon + leaf mass and clover proportion of herbage yield was greater when grown with early‐maturing than with late‐maturing grass cultivars in the field and greenhouse. This indicates that early‐maturity grasses were more compatible with white clover. Individual perennial ryegrass plants had about twice as many tillers per plant (P < 0.01) and yielded 24% more (P < 0.01) dry matter than orchardgrass in mixture with clover. Perennial ryegrass–clover mixtures yielded 20% more herbage and had 40% more tillers per unit area than orchardgrass–clover in the field. Clover plants in monoculture were heavier and more complex in structure than plants in mixture in both field and greenhouse. We conclude that maturity of grass cultivars has an effect on white clover establishment and that early‐maturing cultivars of perennial ryegrass or orchardgrass are more compatible with Will white clover during the establishment phase.
Dryland Winter Wheat as Affected by Previous Crops
Authors: Norwood Charles A.
Published: July 2010

The dryland winter wheat (Triticum aestivum L.)–grain sorghum [Sorghum bicolor (L.) Monech]–fallow (WSF) rotation is suitable for large areas of the U.S. Great Plains. Other crops such as corn (Zea mays L.), sunflower (Helianthus annus L.), and soybean [Glycine max (L.) Merr.] can be substituted for grain sorghum, but the effects of these crops on the subsequent wheat crop have not been extensively documented. A study was conducted near Garden City, KS from 1992 through 1998 to determine the effect of these four crops on soil water at planting (SWP), yield, and yield components of the subsequent wheat crops. Wheat was grown following conventional tillage (CT), reduced tillage (RT), and no tillage (NT). On average, amounts of SWP following sunflower and soybean were 19.9% and 9.3% lower, respectively, than those following corn and sorghum. Grain yields following sunflower averaged 0.85 Mg ha−1 less than those following corn and sorghum in two of six years at all tillage levels, 0.72 Mg ha−1 less in one year with CT and NT, and 0.60 Mg ha−1 less than those following corn in one year with CT and RT. Yields following soybean were 0.61 Mg ha−1 less than those following RT corn in one year and 0.61 Mg ha−1 less than CT corn and CT sorghum in one year. Most of these yield reductions were caused by fewer heads m−2, but fewer kernels head−1 and lower kernel weight occasionally contributed. Sunflower and soybean may cause reductions in subsequent wheat yields, but they provide diversification and may prove beneficial when the whole cropping system is considered.
Spring Wheat Response to Tillage and Nitrogen Fertilization in Rotation with Sunflower and Winter Wheat
Authors: Halvorson Ardell D. , Black Alfred L. , Krupinsky Joseph M. , Merrill Steven D. , Wienhold Brian J. , Tanaka Donald L.
Published: July 2010

Spring wheat (Triticum aestivum L.) is a major crop in the northern Great Plains that is generally grown following a 21‐mo fallow period. A 12‐yr study was conducted to determine the effects of tillage system [conventional‐till (CT), minimum‐till (MT), and no‐till (NT)], N fertilizer rate (34, 67, and 101 kg N ha−1), and cultivar (Butte86 and Stoa) on spring wheat yields within a dryland spring wheat (SW)–winter wheat (WW)–sunflower (Helianthus annuus L.) (SF) rotation. Grain yield responses varied with tillage system, N fertilizer rate, cultivar, and year as indicated by significant tillage × N rate × year and N rate × cultivar × year interactions. In years with >260 mm total plant available water (TPAW) but <400 mm TPAW, NT grain yields were greater than those with CT at the highest N rate, with similar trends at the medium and low N rates. When TPAW exceeded 400 mm, grain yields for CT were generally greater than for NT at the medium N rates. The greatest 12‐yr average grain yield (1727 kg ha−1) was obtained with NT and application of 101 kg N ha−1. Grain yields were lowest during years when TPAW was <300 mm, with only small responses to tillage and N treatments. Cultivars responded similarly to N fertilization in years with >300 mm TPAW, with Butte86 yielding more than Stoa in 6 out of the 12 yr. Soil NO3–N levels increased in the root zone following three consecutive drought years, but had declined to initial year levels by the end of the study. These results indicate that farmers in the northern Great Plains can produce SW following SF in annual cropping systems that do not include a fallow period, particularly if NT or MT systems are used with adequate N fertilization.
Growth and Canopy Characteristics of Field‐Grown Tomato
Authors: Scholberg Johannes , McNeal Brian L. , Jones James W. , Boote Kenneth J. , Stanley Craig D. , Obreza Thomas A.
Published: July 2010

Although detailed growth studies and yield analysis are common for agronomic crops, their application to horticultural crops is limited. Detailed growth measurements of field‐grown tomato (Lycopersicon esculentum Mill.) were conducted at four Florida locations for two irrigation methods. Maximum rate of main‐stem node development was ≈0.5 nodes d−1 and leaf area index (LAI) increased exponentially with main‐stem node number. Maximum LAI was attained 11 wk after transplanting, with values ranging from 1.5 to 3.0 and from 3.2 to 6.0 for drip‐irrigated and subirrigated crops, respectively. Lower LAI values with drip irrigation were only partially related to wider row spacings. Final biomass (dry weight) ranged from 6 to 12 Mg ha−1 and fruit dry weight harvest indices (fruit biomass/total above‐ground biomass) ranged from 0.53 to 0.71. Average dry matter accumulation by roots, stems, and leaves accounted for ≈3, 23, and 17% of final biomass, respectively. Estimated radiation use efficiency (RUE) for tomato averaged 1.05 g dry weight MJ−1 m−2, with 50 to 60% light interception in the crop production area at LAI values of 4 to 5. At 11000 plants per ha, the rate of dry matter accumulation averaged 17.8 g d−1 m−2 during the linear growth phase, with instantaneous dry matter partitioning to fruits averaging 0.70 during the fruit‐growth phase. Relationships between degree days, estimated cumulative intercepted radiation, and fruit yield accounted for much of the variation in fruit yields for these different seasons and locations throughout Florida.
Tillage and Herbicides Affect Burcucumber Management in Corn
Authors: Messersmith David T. , Curran William S. , Roth Gregory W. , Hartwig Nathan L. , Orzolek Michael D.
Published: July 2010

The effect of tillage and herbicide application timing was examined on established populations of burcucumber (Sicyos angulatus L.) in corn (Zea mays L.). The field study consisted of three tillage regimes (moldboard plow/disk, chisel plow/disk, and no‐tillage) and three herbicide treatments: atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] plus the dimethylamine salt of dicamba; 3,6‐dichloro‐2‐methoxybenzoic acid applied preemergence (PRE) or postemergence (POST); and no atrazine plus dicamba (no broadleaf herbicide). Postemergence treatments were applied to 3‐ to 6‐leaf corn and cotyledon to 8‐leaf burcucumber. In two of three field locations, late‐season burcucumber dry weight was approximately 65% less in no‐tillage than in the moldboard plow treatment, while no difference in burcucumber dry weight was observed between chisel plow and no‐tillage treatments. Regardless of tillage system, atrazine plus dicamba applied POST was more effective than PRE applications. Corn grain yield was not affected by tillage treatment, but was higher in both the PRE and POST treatments than in the no broadleaf herbicide treatment. Depth of burcucumber seedling emergence was examined in the greenhouse. Pre‐germinated burcucumber seeds were placed in the soil at 0, 1, 3, 5, 10, 15, and 20 cm deep. Percent emergence was highest in the 1 to 5 cm depth. Less burcucumber emerged from depths of 10 cm or greater or when burcucumber was placed on the soil surface. These data suggest that tillage and herbicide timing can influence burcucumber control.
Dehardening of Annual Bluegrass and Creeping Bentgrass during Late Winter and Early Spring
Authors: Tompkins Darrell K. , Ross James B. , Moroz David L.
Published: July 2010

Changes in cold hardiness levels of annual bluegrass (Poa annua L.) and creeping bentgrass (Agrostis palustris Huds.) were monitored under field conditions during the dehardening period of late winter and early spring. During the course of two spring periods the cold hardiness levels of the two species were monitored in conjunction with the following hydration treatments: snow cover maintained to prolong dormancy, snow removal in March, and hydration of crown tissues in combination with snow removal. Cold hardiness levels, percent crown moisture, and soil temperatures were monitored throughout this period. Cold hardiness levels were significantly influenced by year, species, hydration treatment, and a number of interactions of these factors. Generally, plants dehardened 2 wk earlier in 1997 than in 1996. On 1 April, creeping bentgrass had cold hardiness levels averaging −20°C compared to −13°C for annual bluegrass. By 15 April, creeping bentgrass plants had lost their cold hardiness advantage. Increased soil temperature was the greatest contributor to the loss of hardiness in the spring. An increase in crown moisture of 4% for annual bluegrass and 6% for creeping bentgrass occurred during the period from 25 March to 22 April. Maintaining a snow cover on plots delayed the loss of cold hardiness by 6 to 9 d in 1996 but had no effect in 1997. Maintaining a snow cover also delayed the increase in crown hydration by a week. Plants were able to partially regain cold hardiness when soil temperatures dropped.
Shading during the Early Grain Filling Period Does Not Affect Potential Grain Dry Matter Increase in Rice
Authors: Kobata Tohru , Sugawara Makoto , Takatu Sadanori
Published: July 2010

Shortage of C assimilate supply to rice grain during approximately the first 10 days after heading (DAY10) has been believed to reduce potentiality of grain dry matter increase (GP) and decrease the final grain weight (GF). However, we suspect that assimilate shortage during DAY10 does not determine GF, if assimilate supply during the rest of the grain filling period (GPERIOD) meets subsequent requirements for realizing GP. Our objective was to determine if GP is in fact affected by shortage of assimilate supply caused by shading during DAY10. Plots of rice (Oryza sativa L.) grown under paddy field conditions were subjected to three strengths of shading for DAY10. After the shades were removed, the plots were divided into two groups. Plants in the first group were thinned to half the plant population density, while the second group was left at normal spacing. GF in the unthinned group was reduced depending on the strength of the shade, but weights in the thinned group almost reached those of nonshaded control plants, except in the most heavily shaded plots, where weights were slightly reduced. In pot experiments simulating crop stand, GF all reached those of control plants when the pots were exposed to abundant radiation after being subjected to heavy shading during either the early or mid‐GPERIOD. These results suggest that rice plants are capable of recovering from early reduction in grain growth rate at least until the mid‐GPERIOD, and shortage of available assimilate during DAY10 does not determine GP
Canopy Photosynthesis and Fiber Properties of Normal‐ and Late‐Planted Cotton
Authors: Bauer Philip J. , Frederick James R. , Bradow Judith M. , Sadler E.John , Evans Dean E.
Published: July 2010

Normal‐ and late‐planted cotton (Gossypium hirsutum L.) often differ in fiber properties, especially those properties related to fiber secondary wall characteristics. This field study was conducted to (i) determine the effect of planting date on fiber properties of bolls at two flowering times, and (ii) determine the relationship between fiber properties and canopy photosynthesis during development of those bolls. Cotton (‘Stoneville 453’) was planted on 3 May and 3 June in 1995 and 3 May and 31 May in 1996. Canopy photosynthesis was measured 10 to 12 times on sunny days from initial flowering through the end of the season. Fiber properties were determined on first sympodial position bolls that bloomed during the first and fourth week of flowering (WOF). Maximum canopy photosynthesis was 21% higher in 1996 than in 1995 and lint yield was 22% greater in 1996 than in 1995. Within each year, average maximum canopy photosynthesis did not differ between planting dates, although yield was approximately 30% lower for the late planting date each year. Bolls from the first WOF generally had lower lint percent, higher short fiber content, lower elongation, and lower whiteness index than bolls from the fourth WOF. Micronaire, immature fiber fraction, and fiber cross‐sectional area were linearly related to the amount of canopy photosynthesis that occurred from 15 to 45 d after flowering. Our results are consistent with the hypothesis that assimilate supply influences cotton fiber properties associated with secondary wall characteristics.