Dryland soil chemical properties and crop yields affected by long-term tillage and cropping sequence

Information on the effect of long-term management on soil nutrients and chemical properties is scanty. We examined the 30-year effect of tillage frequency and cropping sequence combination on dryland soil Olsen-P, K, Ca, Mg, Na, SO 4 –S, and Zn concentrations, pH, electrical conductivity (EC), and cation exchange capacity (CEC) at the 0–120 cm depth and annualized crop yield in the northern Great Plains, USA. Treatments were no-till continuous spring wheat (Triticum aestivum L.) (NTCW), spring till continuous spring wheat (STCW), fall and spring till continuous spring wheat (FSTCW), fall and spring till spring wheat–barley (Hordeum vulgare L., 1984–1999) followed by spring wheat–pea (Pisum sativum L., 2000–2013) (FSTW-B/P), and spring till spring wheat-fallow (STW-F, traditional system). At 0–7.5 cm, P, K, Zn, Na, and CEC were 23–60% were greater, but pH, buffer pH, and Ca were 6–31% lower in NTCW, STCW, and FSTW–B/P than STW-F. At 7.5–15 cm, K was 23–52% greater, but pH, buffer pH, and Mg were 3–21% lower in NTCW, STCW, FSTCW, FSTW–B/P than STW-F. At 60–120 cm, soil chemical properties varied with treatments. Annualized crop yield was 23–30% lower in STW-F than the other treatments. Continuous N fertilization probably reduced soil pH, Ca, and Mg, but greater crop residue returned to the soil increased P, K, Na, Zn, and CEC in NTCW and STCW compared to STW-F. Reduced tillage with continuous cropping may be adopted for maintaining long-term soil fertility and crop yields compared with the traditional system

Dryland Soil Carbon and Nitrogen after Thirty Years of Tillage and Cropping Sequence

Little information is available about the long-term impact of tillage and cropping sequence on dryland soil C and N levels in the northern Great Plains. This study provided an opportunity to evaluate the effect of thirty years (1983-2013) of tillage and cropping sequence combination on dryland crop residue and soil organic (SOC) and inorganic C (SIC), soil total N (STN), NH4-N, and NO3-N contents at the 0- to 120-cm depth in eastern Montana. Treatments were no-till continuous spring wheat (NTCW), spring till continuous spring wheat (STCW), fall and spring till continuous spring wheat (FSTCW), fall and spring till spring wheat-barley (1984-1999) followed by spring wheat-pea (2000-2013) (FSTW-B/P), and spring till spring wheat-fallow (STW-F). Mean annualized crop biomass returned to the soil was lower in STW-F than in other treatments. At 0 to 7.5 cm, soil bulk density was greater in STW-F but SOC, SIC, and STN were greater in STCW than in other treatments, except NTCW, in 2013. The SIC at 90 to 120 cm was greater in NTCW and STCW than FSTCW and FSTW-B/P and STN at 30 to 60 cm was greater in NTCW and STW-F than in STCW and FSTW-B/P. The NH4-N content at 0 to 30 cm and NO3-N content at 0 to 120 cm were greater in FSTCW than in other treatments, except STCW. From 1983 to 2013, SOC at 0 to 7.5 cm declined from 104 kg C ha-1 yr-1 in STCW to 214 kg C ha-1 yr-1 in FSTW-B/P. Soil total (organic + inorganic) C was strongly related to SOC (R2 = 0.82, P ≤ 0.001, n = 168). Reduced tillage, followed by increased amount of crop residue returned to the soil, probably increased C and N storage and reduced the rate of decline in NTCW and STCW, but increased tillage intensity increased available N in FSTCW. Soil total C can be used as a substitute for SOC in dryland soils, which reduce the need to measure SIC

Dryland Soil Greenhouse Gas Emissions Affected by Cropping Sequence and Nitrogen Fertilization

Information is needed to mitigate dryland soil greenhouse gas (GHG) emissions by using novel management practices. We evaluated the effects of cropping sequence and N fertilization on dryland soil temperature and water content at the 0- to 15-cm depth and surface CO2, N2O, and CH4 fluxes in a Williams loam (fine-loamy, mixed, superactive, frigid, Typic Argiustolls) in eastern Montana. Treatments were no-tilled continuous malt barley (Hordeum vulgaris L.) (NTCB), no-tilled malt barley–pea (Pisum sativum L.) (NTB–P), and conventional-tilled malt barley–fallow (CTB–F) (control), each with 0 and 80 kg N ha−1. Gas fluxes were measured at 3 to 14 d intervals using static, vented chambers from March to November 2008 to 2011. Soil temperature varied but water content was greater in CTB–F than in other treatments. The GHG fluxes varied with date of sampling, peaking immediately after substantial precipitation (\u3e15 mm) and N fertilization during increased soil temperature. Total CO2 flux from March to November was greater in NTCB and NTB–P with 80 kg N ha−1 than in other treatments from 2008 to 2010. Total N2O flux was greater in NTCB with 0 kg N ha−1 and in NTB–P with 80 kg N ha−1 than in other treatments in 2008 and 2011. Total CH4 uptake was greater with 80 than with 0 kg N ha−1 in NTCB in 2009 and 2011. Because of intermediate level of CO2 equivalent of GHG emissions and known favorable effect on malt barley yield, NTB–P with 0 kg N ha−1 might mitigate GHG emissions and sustain crop yields compared to other treatments in eastern Montana. For accounting global warming potential of management practices, however, additional information on soil C dynamics and CO2 associated with production inputs and machinery use are needed

Comparing Stacked and Alternate-Year Cropping Systems In a Semiarid Environment

Diversification of continuous durum system can improve economic and environmental sustainability in semiarid cropping systems, but little is known about the influence of rotation type and management system on durum performance. We conducted a study from 2005 to 2011 comparing two sets of crops in stacked (durum-durum-canola-pea and durum-durum-flax-pea) and alternate-year (durum-canola-durum-pea and durum-flax-durum-pea) rotations under conventional and ecological management levels on durum yield and characteristics. Continuous durum was included as a control. Conventional management included preplant tillage, broadcast urea, standard seeding rates, and short durum residue height. Ecological management included zero tillage, banded urea at planting, greater seeding rates, and tall durum residue height. Average durum grain yield, plant height, and plant stand across years were lower in durum-durum-canola-pea than other rotations under the conventional but not under the ecological management. Overall, rotation type rarely influenced yield or yield components of durum. Durum yield was greater in three out of six years under the ecological than under the conventional management. Durum was taller, with more reproductive tillers but fewer seed per head, under the ecological than under the conventional management. Stacked rotation of durum with pea in the conventional management resulted in reduced durum grain yield and performance compared to other treatments in dryland cropping systems in the northern Great Plains

Relations of Cercospora beticola with Host Plants and Fungal Antagonists

Cerco pora leaf pot (CLS) cau ed by Cercospora beticola Sacc., is sti ll considered to be the mo t important foliar di ease of ugar beel. The di ea e ha been reported wherever ugar beet i grO\\ n (Bieiholder and Weltzien 1972). Since the di ease wa fir t identified. management of CLS of ugar beet has been an ongoing mi ion of plant pathologists. Toda}. everal trategie are available and applied either s ingly or in combination to manage the di ea e. The e management trategie , which were ummarized by Windels et al. (1998), include cultural practice uch a deep tillage, rotation with non-host crops and identification and elimination of econdary weed host . Other include breeding and use of re i.tant cultivars and application of fungicide. The u e of re i tant sugar beet cultivars has long been an integral pan of CLS management; however, problems associated with selection of re i tant cuhivars again t CLS are wel l documented and were recently reviewed by Weiland and Koch (2004). According to the author , resistance to CLS in sugar beet has been de cribed as quantitatively in herited and rate limiting with respect to disease development (Smith and Gaskill 1970, Ro i et a l. 1999). Although resistant cultivars have proven effective in both North America and Europe, they nonetheless exhibit low heritability (Smith and Ruppel 1974), and cultivar bred for Cercospora resistance can still exhibit leaf pots if climatic condition favorable for the disease occur

Tillage, Crop Rotation, and Cultural Practice Effects on Dryland Soil Carbon Fractions

Information is needed on novel management practices to increase dryland C sequestration and soil quality in the northern Great Plains, USA. We evaluated the effects of tillage, crop rotation, and cultural practice on dryland crop biomass (stems and leaves) yield, surface residue, and soil C fractions at the 0-20 cm depth from 2004 to 2008 in a Williams loam in eastern Montana, USA. Treatments were two tillage (no-tillage [NT] and conventional tillage [CT]), two crop rotations (continuous spring wheat [Triticum aestivum L.] [CW] and spring wheat-barley [Hordeum vulgaris L.] hay-corn [Zea mays L.]-pea [Pisum sativum L.] [W-B-C-P]), and two cultural practices (regular [conventional seed rates and plant spacing, conventional planting date, broadcast N fertilization, and reduced stubble height] and ecological [variable seed rates and plant spacing, delayed planting, banded N fertilization, and increased stubble height]). Carbon fractions were soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop biomass was 24% to 39% greater in W-B-C-P than in CW in 2004 and 2005. Surface residue C was 36% greater in NT than in CT in the regular practice. At 5 - 20 cm, SOC was 14% greater in NT with W-B-C-P and the regular practice than in CT with CW and the ecological practice. In 2007, POC and PCM at 0 - 20 cm were 23 to 54% greater in NT with CW or the regular practice than in CT with CW or the ecological practice. Similarly, MBC at 10 - 20 cm was 70% greater with the regular than with the ecological practice in NT with CW. Surface residue, PCM, and MBC declined from autumn 2007 to spring 2008. No-tillage with the regular cultural practice increased surface residue and soil C storage and microbial biomass and activity compared to conventional tillage with the ecological practice. Mineralization reduced surface residue and soil labile C fractions from autumn to spring

Yield, Pests, and Water Use of Durum and Selected Crucifer Oilseeds in Two-Year Rotations

Cool-season oilseed crops are potential feedstock for biofuel production, but few studies have compared oilseed-durum (Triticum durum Desf.) rotations on yield, quality, water use, and pests associated with crops. We conducted an experiment under dryland conditions during 2007 to 2010 near Culbertson, MT, comparing crop productivity, water balance, and key weed and arthropod pests of 2-yr oilseed-durum rotations under zero tillage. Rotations included durum with three Brassicaceae sp., camelina [Camelina sativa (L.) Crantz], crambe (Crambe abyssinica Hochst. ex R.E. Fries), and canola-quality Brassica juncea L., and fallow. Over 4 yr, B. juncea had the highest seed and oil yields of crucifer entries. Water use was similar among oilseed crops, averaging 286 mm. Water use was similar for durum following oilseeds, averaging 282 mm, 72 mm less than for durum following fallow. Durum following fallow averaged 775 kg ha−1 greater grain yield than durum following oilseeds due to higher water availability and use. Camelina had greater weed biomass at harvest and lower densities of Plutella xylostella L. than other oilseeds. Durum in rotation with crambe had higher weed density and biomass at harvest than durum following B. juncea or fallow. Brassica juncea generally performed better than crambe or camelina, but each oilseed crop had several positive attributes. Oilseed-durum rotations can be used for biofuel feedstock and grain production, but long-term sustainability of 2-yr rotations on crop yields and pest management requires further study

Nitrogen Use in Durum and Selected Brassicaceae Oilseeds in Two-Year Rotations

Brassicaceae oilseeds can serve as potential feedstocks for renewable biofuels to offset demand for petroleum-based alternatives. However, little is known about oilseed crop yield potential and N use in semiarid, wheat (Triticum spp.)-based cropping systems that dominate the northern Great Plains (NGP). A 5-yr study was conducted in northeast Montana to investigate the yield potential of a direct seeded system of durum (T. durumDesf.) in rotation with either chemical fallow or three Brassicaceae oilseeds: camelina [Camelina sativa (L.) Crantz], crambe (Crambe abyssinica Hochst. ex R.E. Fries), and canola-quality Brassica juncea L. Overall, results from the study indicated that seed yield in the three Brassicaceae oilseeds tested in rotation with durum was related (P \u3c 0.001; r2 = 0.68) to a nitrogen recovery index (NRI), indicating the importance of nitrogen use (NU) efficiency in dryland oilseed production, and that B. juncea generally used N more efficiently than crambe and camelina. Similarly, NRI was related (P \u3c 0.001; r2 = 0.72) to grain yield in durum following oilseeds. Grain yield of durum following B. juncea was similar to durum following fallow and greater than durum following camelina or crambe. Durum following crambe tended to use N more inefficiently than durum following camelina, B. juncea, or fallow. Differences in yield and N use of durum and oilseeds varied among years, which underscores the need to further develop management tools to optimize durum-oilseed cropping systems in highly variable rainfall environments typical of the NGP

Morphological and Geochemical Evidence of Eumelanin Preservation in the Feathers of the Early Cretaceous Bird, Gansus yumenensis

Recent studies have shown evidence for the preservation of colour in fossilized soft tissues by imaging melanosomes, melanin pigment containing organelles. This study combines geochemical analyses with morphological observations to investigate the preservation of melanosomes and melanin within feathers of the Early Cretaceous bird, Gansus yumenensis. Scanning electron microscopy reveals structures concordant with those previously identified as eumelanosomes within visually dark areas of the feathers but not in lighter areas or sedimentary matrices. Fourier transform infrared analyses show different spectra for the feathers and their matrices; melanic functional groups appear in the feather including carboxylic acid and ketone groups that are not seen in the matrix. When mapped, the carboxylic acid group absorption faithfully replicates the visually dark areas of the feathers. Electron Paramagnetic Resonance spectroscopy of one specimen demonstrates the presence of organic signals but proved too insensitive to resolve melanin. Pyrolysis gas chromatography mass spectrometry shows a similar distribution of aliphatic material within both feathers that are different from those of their respective matrices. In combination, these techniques strongly suggest that not only do the feathers contain endogenous organic material, but that both geochemical and morphological evidence supports the preservation of original eumelanic pigment residue