Forage yield and crude protein of interseeded legume‐bermudagrass mixtures as affected by phosphorus fertilizer 1

Bermudagrass (Cynodon dactylon L.) is a warm season perennial that is well adapted in the southern Great Plains. It is one of the region's most important forage crops used for livestock production, and is commonly grown without legume interseeding. Recent research has investigated ways of improving the quality and quantity of this forage. The objectives of this study were to determine the effect of interseeded legumes and phosphorus (P) fertilizer on bermudagrass pasture forage yield and crude protein content. One experiment was initiated in 1993 in eastern Oklahoma in an established bermudagrass pasture. Red clover (Trifolium pratense L.), ladino clover (Trifolium repens L.), and two varieties of alfalfa (Medicago sativah), ’alfagraze’ and'common’, were interseeded by hand into an established stand of bermudagrass. The effect of P on forage yield and crude protein was evaluated using a 30‐kg P ha^‐1 rate applied at establishment versus no applied P. Forage yield was collected three times throughout the growing season each year from 1994 through 1997. When both alfalfa varieties were interseeded into a bermudagrass pasture without applying additional P fertilizer, forage yields for the legume‐grass mixtures decreased below those obtained from the monoculture bermudagrass in the first year of the stand. The alfalfa variety ‘alfagraze’ interseeded into established bermudagrass decreased total forage yield over the entire 4‐yr study. Interseeded red clover and ladino clover increased crude protein of the forage compared with monoculture bermudagrass the first two years of the study, with red clover continuing to increase crude protein in the fourth year. However, when 30 kg P ha^‐1 was applied to the bermudagrass prior to establishment of the legumes, no change in yield or protein was observed for both alfalfa varieties’ interseeding treatments versus the unfertilized mixtures. Although forage yield may not be increased, interseeding legumes into established bermudagrass could provide an efficient way to improve pasture crude protein without the use of inorganic fertilizers. However, if alfalfa ('common’ or ‘alfagraze') is interseeded, additional P may need to be applied at legume establishment to prevent possible yield decreases.     

Tillage and Forage System Effects on Forage Yields and Nutrient Uptake under Broiler Litter–Amended Soils

Abstract

Planting and harvesting high‐yielding forage grasses may remove phosphorus (P), copper (Cu), and zinc (Zn) from surface soils with a long history of broiler litter application. A study was conducted in Alabama's Sand Mountain region from 1998 to 2000 to determine tillage and forage systems best suited for removing nutrients from such overloaded soils. Tillage treatments included no‐till, moldboard plowing, chisel plowing, and each combined with paraplowing. Forage treatments included bermudagrass (Cynodon dactylon (L.) Pers.) cv. Russell, tall fescue (Festuca arundinacea Schreb.) cv. Kentucky‐31, and an annual rotation of ryegrass (Lolium multiflorum Lam.) and sorghum sudangrass (Sorghum bicolor L. Moench×Sorghum vulgare sudanense). The annual rotation produced highest yields and P uptake. Moldboard plowing the annual rotation further increased yields. It appears the annual rotation best removes P, Cu, and Zn via plant uptake. Tillage reduced P concentrations in the soil surface in the following order: moldboard>chisel>no‐till.     

Performance of legume–grass mixtures in the West Balkan region

Three perennial legumes (alfalfa, red clover and birdsfoot trefoil) and four cool-season perennial grasses (orchardgrass, tall fescue, Italian ryegrass and red fescue) were grown in legume–grass combinations and in pure stands of individual species, at three locations in the West Balkan region (Novi Sad, Banja Luka and Pristina) in the period from 2012 to 2015. The study evaluated dry matter yield, legume–grass–weed proportion and forage quality. High annual forage yield of legume–grass mixtures can be obtained with proper selection of species and an appropriate legume–grass ratio. However, high and stable yield, particularly in the case of grasses, depends on the amount and schedule of precipitation as well as the cutting time. The mixtures and legume pure stands achieved better forage production both per cutting and on the annual basis and had better forage quality than grass pure stands.     

Assessment of long-term barley–legume rotations in a typical Mediterranean agro-ecosystem: grain and straw yields

Traditional Mediterranean rainfed cereal/fallow systems are being replaced by cereal monoculture due to land-use pressure. Food or forage legumes in rotation with cereals are an alternative sustainable cropping system. Complex cropping systems can only be assessed by long-term trials. This 11-year rainfed barley-based rotation trial in northern Syria assessed rotation effects on yields of barley and legumes, with particular emphasis on the management of vetch. The mean order of barley grain yields from the rotations was: vetch for hay, vetch for grazing > fallow = medic = vetch for seed > lentil, and continuous barley. Straw yields followed a similar pattern. Nitrogen (60 kg ha^?1) increased grain (39%) and straw (65%) yields. The N fertilization of barley had no carryover effect on the alternative legume crops. Although there were no significant differences in seed or straw yield between lentil and vetch, seasonal rainfall influenced overall yields. Total biomass yields were in the order of vetch, medic and lentil. There is a compelling case for annual vetch paired with barley in rotations for the Mediterranean region. Thus, barley/vetch rotations can potentially enhance barley yields and improve soil quality, and provide valuable fodder for small ruminants as well in the region's agricultural systems.     

Preservation of seed viability during 25 years of storage under standard genebank conditions

Maintaining sufficient viability is critical to the sustainability of ex situ conserved seed collections. For this reason, accessions are regenerated when viability falls below a predefined threshold. Viability is monitored by determining the germination ability of accessions at predefined time intervals. Optimizing the frequency of these germination tests, in order to avoid waste of resources, is hampered by the scarce availability of data about seed longevity, particularly for material maintained under genebank conditions. Here we report on the analysis of nearly 40,000 germination test results collected for a wide range of crop species over a 25-years period by the centre for genetic resources, the Netherlands (CGN), where seeds of genebank accessions are dried to 3–7 % moisture content and stored for the long term under near-vacuum in aluminium foil bags at ?20 °C. The results indicate that seed viability is well maintained for the large majority of seed lots during the first 25 years after regeneration as only 3.3 % of the monitoring tests revealed below-threshold germination values. It is argued that the majority of these sub-standard seed lots are due to other causes than seed ageing, including dormancy problems and estimation error in germination testing. For material, maintained under the seed management procedures and storage conditions practiced by CGN, it is therefore recommended to delay the first germination monitoring tests to 25 years after regeneration.     

Evapotranspiration of irrigated and rainfed maize–soybean cropping systems

We have been making year-round measurements of mass and energy exchange in three cropping systems: (a) irrigated continuous maize, (b) irrigated maize–soybean rotation, and (c) rainfed maize–soybean rotation in eastern Nebraska since 2001. In this paper, we present results on evapotranspiration (ET) of these crops for the first 5 years of our study. Growing season ET in the irrigated and rainfed maize averaged 548 and 482 mm, respectively. In irrigated and rainfed soybean, the average growing season ET was 452 and 431 mm, respectively. On average, the maize ET was higher than the soybean ET by 18% for irrigated crops and by 11% for rainfed crops. The mid-season crop coefficient K_c (=ET/ET₀ and ET₀ is the reference ET) for irrigated maize was 1.03 ± 0.07. For rainfed maize, significant dry-down conditions prevailed and mid-season K_c was 0.84 ± 0.20. For irrigated soybean, the mid-season K_c was 0.98 ± 0.02. The mid-season dry down in rainfed soybean years was not severe and the K_c (0.90 ± 0.13) was only slightly lower than the values for the irrigated fields. Non-growing season evaporation ranged from 100 to 172 mm and contributed about 16–28% of the annual ET in irrigated/rainfed maize and 24–26% in irrigated/rainfed soybean. The amount of surface mulch biomass explained 71% of the variability in non-growing season evaporation totals. Water use efficiency (or biomass transpiration efficiency), defined as the ratio of total plant biomass (Y_DM) to growing season transpiration (T) was 5.20 ± 0.34 and 5.22 ± 0.36 g kg^?1, respectively for irrigated and rainfed maize crops. Similarly, the biomass transpiration efficiency for irrigated and rainfed soybean crops was 3.21 ± 0.35 and 2.96 ± 0.30 g kg^?1. Thus, the respective biomass transpiration efficiency of these crops was nearly constant regardless of rainfall and irrigation.     

Legume–barley intercropping stimulates soil N supply and crop yield in the succeeding durum wheat in a rotation under rainfed conditions

Legume–cereal intercropping is increasingly being appreciated in dryland areas, where severe climatic conditions and intensive agricultural practices, generally dominated by continuous cereal cultivation, determine depletion of soil nutrient resources and decline of soil fertility. This research aimed to assess whether and to what extent a newly introduced legume-based intercropping system is able to ameliorate the biological fertility status of an arable soil in a way that is still noticeable during the succeeding durum wheat cropping season in terms of changes in bacterial community structure, soil C and N pools, and crop yield. A field experiment was carried out under rainfed conditions in Southern Italy on a sandy clay loam soil cultivated with durum wheat following in the rotation a recently established grain legume (pea, faba bean)–barley intercropping. Soil chemical, biochemical and eco-physiological variables together with compositional shifts in the bacterial community structure by LH-PCR fingerprinting were determined at four sampling times during the durum wheat cropping season. Soil fertility was estimated by using a revised version of the biological fertility index. Results showed that even though the microbial biomass was significantly altered, the preceding legume intercrops stimulated C-related functional variables thus leading to an increased release of mineral N, which was larger in crop treatments succeeding pea-based than faba bean-based intercropping. The increased N made available in soil enabled the succeeding durum wheat to achieve an adequate grain yield with a reduced N-fertilizer use. Soil type and environmental conditions rather than crop treatments were major determinants of bacterial community structure. The biological fertility status was not varied, suggesting that in intensively managed rainfed areas long-term crop rotations with intercropped legumes are needed to consistently ameliorate it.     

Seasonal development of biomass yield in grass–legume mixtures on different soils and development of above- and belowground organs of Medicago sativa

Grass–legume mixtures are suitable for crop rotations under organic farming. Little attention has been paid to seasonal development of mixtures with alfalfa under field conditions. We investigated the effects of site and cut on herbage and belowground biomass yields of grass–legume mixture and on above- and belowground traits of Medicago sativa. Six sites in southern Germany were monitored during 2011. Dry matter herbage yield ranged from 9 to 16 t ha^?1. The total herbage yield of three cuts per year decreased from 45% to 36% and 19%. The belowground biomass in the upper 30 cm soil layer ranged from 1.7 to 3.8 t ha^?1.There was no seasonal trend. Diameter of the root neck and maximum order of branching of alfalfa increased during the season. The number of nodules per plant decreased from 9.5–17.0 in May to 7.5–13.0 in August. By the last cut, roots with larger diameter created smaller nodules. More branched roots created more nodules independent of their shape. Thinner roots have more active nodules. Plant height, number of stems and inflorescences per plant were higher in July and August than in May. In conclusion, a holistic analysis including above- and belowground traits should be used for the evaluation of fodder crops.     

Long-term fertilization effects on crop yields,soil fertility and sustainability in the Static Fertilization Experiment Bad Lauchstädt under climatic conditions 2001–2010

The Static Fertilization Experiment Bad Lauchstädt (1902) consists of a crop rotation of sugar beets, spring barley, potatoes and winter wheat. Three farmyard manure (FYM) treatments and six mineral fertilizer treatments are combined orthogonally. Comparing the first and last decades, crop yields nearly doubled. In unfertilized plots, yields and N uptake by crops also increased when comparing first and last decades. On average for the decade 2001–2010, N uptake in unfertilized plots amounted 51.6 kg ha^?1. Although soil organic carbon (SOC) levels for unfertilized plots remain almost unchanged, SOC increases slowly in the most highly fertilized treatment, resulting in a gradual widening of differences in SOC between the most extreme treatments to 0.952%. Climate change and increased harvesting and root residues due to rising yields are suggested as an explanation. Except for the plot with the highest application of mineral and organic fertilizer, in all treatments more N was taken up by crops than was applied by fertilizers. Higher FYM input leads to more unfavourable N balances because N release from FYM cannot be controlled. Considering atmospheric N input, only in the exclusively mineral fertilized treatment is N balanced out. Similar results are found for C balances: the exclusively mineral fertilized treatment shows the most favourable C balance.     

Evaluation of rice–legume–rice cropping system on grain yield,nutrient uptake,nitrogen fixation,and chemical,physical, and biological properties of soil

To achieve higher yields and better soil quality under rice–legume–rice (RLR) rotation in a rainfed production system, we formulated integrated nutrient management (INM) comprised of Azospirillum (Azo), Rhizobium (Rh), and phosphate-solubilizing bacteria (PSB) with phosphate rock (PR), compost, and muriate of potash (MOP). Performance of bacterial bioinoculants was evaluated by determining grain yield, nitrogenase activity, uptake and balance of N, P, and Zn, changes in water stability and distribution of soil aggregates, soil organic C and pH, fungal/bacterial biomass C ratio, casting activities of earthworms, and bacterial community composition using denaturing gradient gel electrophoresis (DGGE) fingerprinting. The performance comparison was made against the prevailing farmers’ nutrient management practices [N/P₂O₅/K₂O at 40:20:20 kg ha⁻¹ for rice and 20:30:20 kg ha⁻¹ for legume as urea/single super-phosphate/MOP (urea/SSP/MOP)]. Cumulative grain yields of crops increased by 7–16% per RLR rotation and removal of N and P by six crops of 2 years rotation increased significantly (P < 0.05) in bacterial bioinoculants-based INM plots over that in compost alone or urea/SSP/MOP plots. Apparent loss of soil total N and P at 0–15 cm soil depth was minimum and apparent N gain at 15–30 cm depth was maximum in Azo/Rh plus PSB dual INM plots. Zinc uptake by rice crop and diethylenetriaminepentaacetate-extractable Zn content in soil increased significantly (P < 0.05) in bacterial bioinoculants-based INM plots compared to other nutrient management plots. Total organic C content in soil declined at 0–15 cm depth and increased at 15–30 cm depth in all nutrient management plots after a 2-year crop cycle; however, bacterial bioinoculants-based INM plots showed minimum loss and maximum gain of total organic C content in the corresponding soil depths. Water-stable aggregation and distribution of soil aggregates in 53–250- and 250–2,000 μm classes increased significantly (P < 0.05) in bacterial bioinoculants-based INM plots compared to other nutrient management plots. Fungal/bacterial biomass C ratio seems to be a more reliable indicator of C and N dynamics in acidic soils than total microbial biomass C. Compost alone or Azo/Rh plus PSB dual INM plots showed significantly (P < 0.05) higher numbers of earthworms’ casts compared to urea/SSP/MOP alone and bacterial bioinoculants with urea or SSP-applied plots. Hierarchical cluster analysis based on similarity matrix of DGGE profiles revealed changes in bacterial community composition in soils due to differences in nutrient management, and these changes were seen to occur according to the states of C and N dynamics in acidic soil under RLR rotation.     

Maize growth and yield responses to seed‐inoculated N2‐fixing bacteria under Dryland production conditions

Maize (Zea Mays L.) seeds were inoculated with the N₂‐fixing bacteria, Azospirillum brasilense and Azorhizobium caulinodans. Shoot growth, shoot nitrogen (N) concentration, and grain yield was determined under dryland production conditions in a silt loam. Fertilizer N was applied according to soil test recommendations at either 0, 50, 75, or 100% of the recommended N requirements for a 7,500 kg ha^‐1 yield goal. Both A. brasilense and A. caulinodans increased shoot dry matter production, shoot N concentration, and grain yield somewhat at the lower N recommended rates. There was no agronomic benefit with either A. brasilense and A. caulinodans inoculations under dryland conditions for high N fertility soils under dryland production conditions in a subhumid or semi‐arid moisture regime.     

Effect of long-term balanced and imbalanced inorganic fertilizer and FYM application on chemical fraction of DTPA-extractable micronutrients and yields under rice–wheat cropping system in mollisols

The imbalanced use of chemical fertilizers under intensive cultivation practices over a period of years leads to various soil-associated problems particularly nutrient availability. Thus, to examine the effect of long-term application of balanced and imbalanced inorganic fertilizer and farm yard manure (FYM) application on the chemical fraction of DTPA-extractable micronutrients under rice–wheat cropping system after 29 years, the observations were recorded from the ongoing field experiment at Govind Ballabh Pant University of Agriculture and Technology, Pantnagar, India. An application of balanced inorganic fertilizer with FYM in rice, while without FYM in wheat significantly improved the DTPA-extractable Zn, Fe, Mn and Cu after rice and wheat crops in both the surface and sub-surface soil layers. Lowest DTPA-extractable Zn, Fe, Mn and Cu were recorded, in surface and sub-surface soil under rice and wheat crops in control. The highest DTPA-extractable Zn, in both surface and sub-surface layers of rice (3.31, 1.62 mg kg⁻¹, respectively) and wheat (2.96, 0.99 mg kg⁻¹, respectively) was recorded because of application of N₁₈₀+P₈₀+K₄₀+Zn(F) + FYM in rice and N₁₈₀+P₈₀+K₄₀+Zn(F) in wheat. However, the DTPA-extractable Fe, Mn and Cu were highest in rice and wheat because of N₁₂₀+P₄₀+K₄₀+FYM and N₁₂₀+P₄₀+K₄₀ application, respectively. The balanced use of inorganic fertilizer with FYM (N₁₈₀+P₈₀+K₄₀+Zn(F) + FYM) in rice and without FYM [N₁₈₀+P₈₀+K₄₀+Zn(F)] in wheat supported the highest rice (6.74 t ha⁻¹) and wheat (3.50 t ha⁻¹) grain yields, while lowest in control. Based on the study results, long-term application of FYM at 5 tonnes ha⁻¹ in rice crop sustained the availability of DTPA-extractable cationic micronutrients to rice and wheat in Mollisols.     

Yield,forage quality,and nitrogen recovery rates of double‐cropped millet and ryegrass

Abstract

Pearl millet and annual ryegrass were continually doubled‐cropped on Olivier silt loam soil for seven years at six levels of N, applied as ammonium nitrate in three applications to millet and in two applications to ryegrass. Forage yields increased as N application rates increased. During seven years at the 0 and 448 kg/ha N rate, millet produced 35% and 95%, respectively, as much yield as it produced at the 800 kg/ha N rate, while comparable values for ryegrass were 19% and 83%. At 448 kg/ha of N the two grasses produced a combined yield of over 20 Mg/ha of dry forage per year. Ryegrass yields following millet were consistently lower than yields previously obtained at this site.

Nitrogen applications consistently increased concentrations of N, Ca, and Mg in both forage grasses, while effects on P and K were variable and S concentrations were unaffected. The amounts of all nutrients removed in the forages were increased as yields increased with N application rates. Nitrate‐N levels considered to be toxic to ruminant animals occurred only where N applications exceeded 170 kg/ha at any one time. In vitro digestibility of each grass was consistently increased by N applications.

The percentage of fertilizer N that was removed in the crops ranged from 66% to 68% for millet and from 35 to 52% for ryegrass as N applications increased up to 448 kg/ha. Residual ammonium and nitrate levels in the top 1.2 m of soil were not increased by N rates of 448 kg/ha or lower. At the 800 kg/ha N‐rate, the apparent N recovery rate decreased and residual ammonium and nitrate levels increased throughout the soil profile.     

Structural transformation of Miscanthus × giganteus lignin fractionated under mild formosolv, basic organosolv, and cellulolytic enzyme conditions

Detailed chemical structural elucidation of lignin fractions from Miscanthus × giganteus was performed by several analytical techniques. Mild formosolv, basic organosolv, and cellulolytic enzyme treatments were applied to isolate three lignin fractions (AL, BL, and CL, respectively), and their structural characterization was comparatively evaluated. Both non-destructive techniques [e.g., Fourier transform infrared (FTIR) spectroscopy, size-exclusion chromatography (SEC), and two-dimensional (2D) nuclear magnetic resonance (NMR)] and degradation methods [e.g., acidic hydrolysis, derivatization followed by reductive cleavage (DFRC), and thioacidolysis] were used. The analysis revealed that a certain amount of carbohydrates (12.8%) was associated with CL and partially led to its increased molecular weight determined by SEC before acetylation. β-O-4 linkages were determined to be the predominant interunits (82%), but also, extensively acylated structures were observed. Alkaline organosolv treatment significantly improved the purity of the lignin fraction (carbohydrate content of 1.0%) and basically kept the original structure of the lignin macromolecule. Under acidic conditions, not only the portion of aryl alkyl ether bonds were cleaved but also new carbon-carbon bonds were formed by condensation reactions, resulting in an increment of the lignin molecular weights. Guaiacyl units were more reactive toward condensation than syringyl units, which was evidenced by an increasing S/G ratio from 0.7 (CL) to 1.7 (AL).     

Long-term fertilization effects on carbon pools and carbon management index of loamy soil under grass–forage legumes mixture in semi-arid environment

ABSTRACT

Soil organic carbon (SOC) is a key component for sustaining crop production. A field experiment was conducted during 2004–2018 to assess the changes in soil carbon fractions under different fertilization practices in grass-legumes mixture. The result indicates that application of farmyard manure (FYM) at 80 Mg ha^–1 has increased SOC concentration leading to carbon sequestration rate of 4.2 Mg ha^–1 year^–1. Further, it has increased the proportion of labile carbon in the total SOC and have accumulated 126, 60, 83 and 95% higher very labile, labile, less labile and non-labile C stock than that of control plot, respectively, in top 30 cm soil layer. Inorganic fertilization and FYM 20 Mg ha^–1 influenced SOC concentration, SOC stock and C sequestration rate similarly. The highest carbon management index (264) was found in the treatment receiving FYM 80 Mg ha^–1 and it was positively correlated with SOC (r = 0.84**). The sensitivity index of the SOC varied from 26 to 152% and the differences were greatest in FYM treatments. The result indicates that grass-legumes mixture build-up the SOC in long term and the addition of FYM further increases it.     

Growth and rhizosphere P pools of legume–wheat rotations at low P supply

Legume pre-crops may increase P uptake of the following wheat, but the mechanisms behind this effect are unclear. A rotation study was carried out to assess the concentrations of rhizosphere P pools of three grain legumes and wheat (phase 1) and their effects on P uptake and P pools in the rhizosphere of the following wheat (phase 2). Faba bean, chickpea, white lupin and wheat were grown for 10 weeks in a loamy sand soil with low P availability. The following wheat was grown in the pre-crop soil with and without addition of pre-crop residues. Among the pre-crops, white lupin had the strongest effect on the P pools; it depleted the labile P pools, resin P and NaHCO₃-Pi and also the less labile P pools, NaOH-Pi and residual P; whereas the concentration of NaHCO₃-Po was higher than that in the rhizosphere of the other pre-crops. White lupin had a smaller biomass compared to faba bean which depleted the P pools to a lesser extent. Phosphorus uptake of the following wheat was greatest in white lupin pre-crop soil. Chickpea increased P uptake of the following wheat when residues were added. In the presence of residues, wheat after legumes depleted labile P pools to a greater extent than wheat after wheat, but this coincided with greater P uptake only in wheat after chickpea and white lupin, which may be explained by the small root biomass of wheat after faba bean. The results show that the greater P uptake of the following wheat induced by pre-crops may be due to two mechanisms: P mobilisation (white lupin) or P addition with legume residues (chickpea). This study further showed that P uptake by a crop is only partly a function of the depletion of P in the rhizosphere; another important factor is the ability to exploit a large soil volume.     

Cover Crop Seeding Rate Effects on Forage Yields of Oat and Barley and Underseeded Bromegrass–Alfalfa Mixture

Annual cover crops compete with underseeded perennial forages for light, moisture, and nutrients and may suppress their establishment and growth. Field experiments were established in 2000 and 2001 at Nipawin and in 2002 and 2003 at Melfort in northeastern Saskatchewan to determine the effects of seeding rates of cover crops of oat (19, 38, and 112 kg ha^?1) and barley (31, 62, and 124 kg ha^?1) on forage dry-matter yield (DMY) of the cover crop cut as greenfeed in the seeding year, DMY of the underseeded meadow bromegrass–alfalfa mixture in the following 1 or 2 years after establishment, and forage quality [concentration of crude protein (CP), acid detergent fiber (ADF) and neutral detergent fiber (NDF)]. In the first establishment year, the no cover crop treatment produced considerably less DMY than the treatments with cover crops. Oat seeded at 112 kg ha^?1 produced greater DMY than when it was seeded at 19 or 38 kg ha^?1 in all four site-years, but DMY differences between the 19 or 38 kg ha^?1 seeding rates were not significant in any site-year. For barley, there was no significant difference in DMY among the three seeding rates in 2000, 2001, and 2002. In 2003, barley seeded at 62 or 124 kg ha^?1 produced greater DMY than when it was seeded at 31 kg ha^?1, but DMYs were not significantly different between the 62 and 124 kg ha^?1 seeding rates. The use of a cover crop did reduce DMY in 2003 of bromegrass–alfalfa mixture underseeded in 2002, but the type of cover crop and its seeding rate did not appear to affect DMY in any site-year. Forage quality in the seeding year was consistently superior in no cover crop treatment compared to that in treatments with cover crops, especially related to CP concentration. There was no consistent trend of forage quality in the cover crop treatments, indicating cover crops and their seeding rates had little effect on forage quality. In conclusion, oat appeared to be more sensitive to seeding rate than barley for forage DMY in the establishment year, but in the subsequent 1 or 2 years after establishment there was little effect of cover crop type and its seeding rate on DMY of bromegrass–alfalfa mixture, although DMY was considerably greater in the no cover treatment than that in treatments with cover crops in 1 site-year.     

Biomass Production,Forage Quality,and Cation Uptake of Quail Bush,Four‐Wing Saltbush,and Seaside Barley irrigated with Moderately Saline–Sodic Water

Abstract: Beneficial use of water of impaired quality has gained attention globally as society's demand for domestic quality water has increased. Additionally, concerns about the environmental implications of disposal of water of impaired quality have necessitated assessment of alternatives to disposal of such water. The study reported here investigated capacity of Atriplex lentiformis (Torr.) S. Wats. (Quail bush), Atriplex X aptera A. Nels. (pro sp.) (Wytana four‐wing saltbush), and Hordeum marinum Huds. (seaside barley) to produce biomass and crude protein and take up cations when irrigated with moderately saline–sodic water, in the presence of a shallow water table. Water tables were established at 0.38, 0.76, and 1.14 m below the surface in sand‐filled columns. The columns were then planted to the study species. Study plants were irrigated for 224 days; irrigation water was supplied every 7 days equal to water lost to evapotranspiration (ET) plus 100 mL (the volume of water removed in the most previous soil solution sampling). Water representing one of two irrigation sources was used: Powder River (PR) [electrical conductivity (EC) = 0.19 Sm^?1, sodium adsorption ratio (SAR) = 3.5 (mmol_c L^?1)^1/2 ] or coalbed natural gas (CBNG) wastewater [EC = 0.35 Sm^?1, SAR = 10.5 (mmol_c L^?1)^1/2]. Biomass production did not differ significantly between water quality treatments but did differ significantly among species and water table depth within species. Averaged across water quality treatments, Hordeum marinum produced 79% more biomass than A. lentiformis and 122% more biomass than Atriplex X aptera, but contained only 11% crude protein compared to 16% crude protein in A. lentiformis and 14% crude protein in Atriplex X aptera. Atriplex spp. grown in columns with the water table at 0.38 m depth produced more biomass, took up less calcium (Ca²⁺) on a percentage basis [(g Ca²⁺ g^?1 biomass) ×100], and took up more sodium (Na⁺) on a percentage basis than when grown with the water table at a deeper depth. Uptake of cations by Atriplex lentiformis was approximately twice the uptake of cations by Atriplex X aptera and three times that of H. marinum. After 224 days of irrigation, crop growth, and cation uptake, followed by biomass harvest, EC and SAR of shallow groundwater in columns planted to A. lentiformis were less than EC and SAR of shallow ground water in columns planted to either of the other species.     

Quantifying the uncertainties of transpiration calculations with the Penman–Monteith equation under different climate and optimum water supply conditions

The uncertainties of transpiration calculations with the Penman–Monteith equation were quantified under different climate conditions of Brazil, Germany and Israel using maize as a common crop type. All experiments were carried out under non-limiting growing conditions. Canopy resistance was determined by scaling to canopy level specific relations between in situ measurements of incident radiation and stomatal conductance using a light penetration model. The model was tested against heat-pulse measured sap flow in plant stems. The root mean square error (RMSE) of daily calculated transpiration minus measured sap flow was 0.4 mm/day. It was dominated by its variance component (variance = 0.2 {mm/day}²; bias = 0.0 mm/day). Calculated transpiration closely matched the measured trends at the three locations. No significant differences were found between seasons and locations. Uncertainties of canopy conductance parameterizations led to errors of up to 2.1 mm/day. The model responded most sensitively to a 30% change of net radiation (absolute bias error = 1.6 mm/day), followed by corresponding alterations of canopy resistances (0.8 mm/day), vapour pressure deficits (0.5 mm/day) and aerodynamic resistances (0.34 mm/day). Measured and calculated 30-min or hourly averaged transpiration rates are highly correlated (r² = 0.95; n = 10634), and the slope of the regression line is close to unity. The overall RMSE of calculated transpiration minus measured sap flow was 0.08 mm/h and was dominated by its variance component (0.005 {mm/h}²). Measured sap flow consistently lagged behind calculated transpiration, because plant hydraulic capacitance delays the change of leaf water potential that drives water uptake. Calculated transpiration significantly overestimated sap flow during morning hours (mean = 0.068 mm/h, n = 321) and underestimated it during afternoon hours (mean = ?0.065 mm/h; n = 316). The Penman–Monteith approach as implemented in the present study is sufficiently sensitive to detect small differences between transpiration and water uptake and provides a robust tool to manage plant water supply under unstressed conditions.