Wheat Monoculture Research Articles

Survey of take-all (Gaeumannomyces tritici) on cereals in Tunisia and impact of crop sequences

Cereal cultivation is a major component of Tunisian agriculture. Take-all of cereals caused by the soil-borne ascomycete Gaeumannomyces tritici (syn.Gaeumannomyces graminis var. tritici) and G. avenae (syn. G. graminis. var. avenae) is a common disease worldwide. The objectives of this study were to evaluate the incidence and distribution of the disease across the cereal growing areas in different climatic regions of Tunisia, to assess the relative importance of the two species, and to investigate the impact of crop sequences on inoculum density in soil and disease incidence.During the cropping seasons of 2009/10, 2010/11, 2012/13, and 2013/14, the percentage of fields infested varied from 8.1% in 2011 to 39.6% in 2013 and the incidence of take-all varied from 0 to 60% in the 298 fields surveyed. Disease incidence was significantly higher in wetter climatic regions than in semi-arid regions. The disease was not detected in the driest area. The highest incidence of take-all was recorded in durum wheat fields. However, overall, no significant differences were observed in the incidence between durum wheat, bread wheat, and barley crops. Take-all was not detected in any oat crop. All findings in this study including surveys, molecular identification of isolated fungi, and determination of DNA concentration in soil, indicate that G. tritici is the dominant species and that G. avenae is rarely found in Tunisian cereal cropping soils.Rotation trials conducted over four cropping seasons on the experimental station showed that a one year break crop could significantly reduce the incidence and severity of take-all in durum wheat. In addition, the inoculum density of Gt/Ga in soil estimated by quantitative PCR was significantly reduced after a legume crop compared to monoculture of durum wheat, and consequently there was a significant decrease in the incidence and severity of the disease in the following year.This study highlights the influence of climatic conditions on the distribution of take-all in the cereal growing areas of Tunisia and the importance of rotation in reducing incidence and severity of take-all.

IDENTIFICATION WHEAT GENOTYPES RESISTANT TO TAN SPOT PYRENOPHORA TRITICI-REPENTIS

Intensified wheat production, changes in cultural practices including shifts from conventional tillage to reduced tillage practices, and wheat monoculture involving cultivation of susceptible cultivars has resulted in development of tan spot to epidemic proportions in Kazakhstan. Pyrenophora tritici-repentis, causal agent of tan spot on wheat. In recent years, there has been increasing distribution and harmfulness of P. tritici-repentis on wheat. The aim of the study was to identify and select wheat germplasm resistant to tan spot P. tritici-repentis using molecular markers. The results of field evaluation showed resistant reaction to tan spot in 76 wheat varieties (68%). Molecular screening of wheat germplasm was carried out based on the reaction to the fungal inoculum and to host-specific toxins (HST) produced by the P. tritici-repentis. The wheat germplasm insensitive to the toxins HST Ptr ToxA and Ptr ToxB was selected. As a result of molecular screening of 111 wheat genotypes using SSR marker Xfcp623 linked to insensitivity gene to the selective toxin Ptr ToxA of tan spot, 31 carriers of effective tsn1 gene were identified, which accounted for 27,9% of the genotypes studied. Ten samples of wheat (Jubileynaya 60, TOO11/TOOOO7, F3.71/TRM/VORONA/3/OC14, NANJTNG 82149 KAUZ, ECHA/LI115, Akmola 2, Kazakh-stanskaya rannespelaya, Kazakhstanskaya 25, 428g/MK-122A and 190-Naz/GF55) are characterized with complex resistance to the races Ptr 1 and 5, as well as to 2 toxins (ToxA and ToxB) and to the Septoria nodorum blotch isolate SNB7k. 20 promising wheat lines resistant to tan spot were selected. These genotypes also showed a moderate and high level of field resistance and recommended to use in the breeding programs for resistance to tan spot.

Efficiency, Profitability and Carbon Footprint of Different Management Programs under No-Till to Control Herbicide Resistant Papaver rhoeas.

The present work examines the effects of different integrated weed management (IWM) programs on multiple herbicide-resistant Papaver rhoeas populations in terms of effectiveness, profitability and carbon footprint. With this aim a trial was established in a winter cereal field under no-till in North-Eastern Spain during three consecutive seasons. Four IWM programs with different intensification levels, from less (crop rotation, mechanical control, and no herbicides) to more intense (wheat monoculture with high chemical inputs), were established. The different strategies integrated in the four programs were efficient in managing the weed after three years, with increased effectiveness after management program intensification. Whereas low input program (which includes fallow season) represented less economic cost than the other programs, on average, no differences were observed on carbon foot print, considered as kg CO2eq kg−1 product, between the different programs, except in the crop rotation program due to the low pea yield obtained. The results from this study show that in the search for a balance between crop profitability and reduction of the carbon footprint while controlling an herbicide resistant population is challenging, and particularly under no-till. In this scenario the short term priority should be to reduce the presence of multiple herbicide resistant biotypes integrating the different available chemical, cultural, and physical strategies.

The Effects of Catch Crops and Tillage Systems on Selected Physical Properties and Enzymatic Activity of Loess Soil in a Spring Wheat Monoculture

This study was aimed at comparing physical soil quality parameters and soil enzymatic activity in a three-year spring wheat monoculture affected by the incorporation of biomass of selected catch crops into the soil using two systems of tillage (conventional plough tillage and conservation tillage). We tested the suitability of the following catch crop plants: white mustard, lacy phacelia, and mixed legumes (faba bean + spring vetch) and compared these to the control treatment. This research was carried out in the period 2014–2016 in Czesławice (central Lublin region, Poland). Catch crops promoted improved soil structure, soil particle-size distribution, soil bulk density, and soil moisture content. Tillage systems had a smaller impact on the soil physical parameters. Plough tillage contributed to improved soil moisture content in a deeper layer (15–20 cm). On the other hand, the above-mentioned tillage system influenced adversely soil compaction and bulk density. Catch crops caused an improvement in the soil particle size distribution, resulting in a higher percentage of the finer soil fractions. Moreover, the catch crops positively affected soil bulk density and soil compaction. The study has proven that enzymatic tests are good indicators to discriminate between soil sites under study in dependence on the catch crop and tillage system. Conservation tillage significantly stimulated the activities of the studied enzymes, especially in the topsoil layers. A particularly wide range of dehydrogenase and urease activity was obtained in the soil sown with the white mustard catch crop. The other catch crops (lacy phacelia and faba bean + spring vetch) also stimulated enzymatic activity. The obtained results show the positive role of catch crops and conservation tillage in bringing about positive changes occurring in the soil environment.

Influence of Tillage Systems, and Forms and Rates of Nitrogen Fertilizers on CO2 and N2O Fluxes from Winter Wheat Cultivation in Oklahoma

Cultivation of winter wheat under reduced tillage systems is increasing in the U.S. Southern Great Plains. Likewise, there is revived interest for including summer legumes in monocultures of winter wheat as green sources of nitrogen (N). This study investigated the influence of tillage systems (no- and conventional tillage), and source and rates of N fertilizer (0, 45 and 90 kg N ha−1 yr−1 in inorganic N fertilizer, and cowpea as green manure) on emissions of carbon dioxide (CO2) and nitrous oxide (N2O) from winter wheat cultivation. The study was conducted within a long-term field experiment initiated in 2011, at upland and bottomland sites near El Reno, Oklahoma during the 2016–2017 growing season of winter wheat. The experiment was conducted site-wise as split-plots in a completely randomized design, with N treatment as main plots and tillage system as subplots. Thus, there were a total of eight treatment combinations with three replicated plots (4 m × 10 m) in each combination in both sites. Net ecosystem exchange (NEE) of CO2 was measured by a closed chamber connected to an infra-red gas analyzer, and fluxes were partitioned to gross primary production (GPP) and ecosystem respiration (ER). Heterotrophic soil respiration (SR) was measured on bare soil spots. Fluxes of N2O were measured with an opaque closed chamber system with a portable gas analyzer. Dynamics of canopy CO2 fluxes (NEE, GPP and ER) were similar between tillage systems, while canopy CO2 fluxes increased with rate of N fertilization. Canopy CO2 fluxes from cowpea and an unfertilized control were similar, and the lowest, due to poor growth of winter wheat compared to the N fertilized treatments. Fluxes of N2O approximated zero from all treatments throughout the study and no response of N fertilizer or tillage system was seen. In conclusion, the results from this study indicated that canopy fluxes of CO2 from winter wheat are controlled by forms and rates of N fertilizers rather than tillage systems.

Las enseñanzas de Don Jesús: Una forma yaqui de agroecología

El objetivo del presente trabajo fue realizar una aproximación para comparar el nivel de sustentabilidad entre el sistema monocultivo trigo y un sistema diversificado presentes en el Valle del Yaqui, lugar donde nació la llamada Revolución Verde y se encuentra localizado en el Sur de Sonora, México. Los ejes del análisis son la innovación, el consumo del agua y la rentabilidad. La metodología aplicada para la realización del presente estudio es una modificación al Marco para la Evaluación de Sistemas de Manejo de Recursos Naturales Incorporando Indicadores de Sustentabilidad (MESMIS). Los resultados indican que, de los 13 indicadores de sustentabilidad evaluados, el sistema diversificado presenta más indicios de sustentabilidad.

Influence of Soil Fertilization Systems on Chemical Properties of the Soil

The purpose of this research has been to determine the influence of soil fertilizations systems (fertilization with: nitrogen, phosphorous, nitrogen and phosphorous, farmyard manure) on the chemical properties (magnesium, aluminium, potassium, calcium, iron and chlorine) of the soil. The experiments have been carried out in the experimental field of National Agricultural Research and Development Institute - Fundulea, Romania, for a wheat monoculture. The lowest values of the metal content in soil (aluminium) have been recorded for wheat experimental variant - fertilized with azote and phosphorous N90P75 (154.8 mg/kg d.m.).Chlorine have the highest content in soil (31.02 mg/100 g soil, 15-30 cm working depth, parcel fertilized with azote 90 kg N/ha) in comparation with the other chemical properties of the soil (content of magnesium, aluminium, potassium, calcium and iron). Keywords: magnesium, aluminium, potassium, calcium, iron, chlorine, farmyard manure, wheat, monoculture

Sustainable Wheat Based Crop Rotation System in Tropical

Cropping systems in the Ethiopian highlands consist primarily of cereals in rotation with grain legume and oilseed crops. Bread Wheat (Triticumaestivum L.) is the dominant crop in wheat belt of Ethiopia and its production is mainly challenged by continuous wheat cropping year after year. Verification of wheat based crop rotation was conducted in Aris zone during 2014 and 2015 cropping seasons. The objective was to break down wheat monoculture and thereby enhance productivity and sustainability of wheat-based farming systems. Rotational crops included rapeseed (Brassica carinata L.), faba bean (Vicia faba L.) and continuous wheat. In second trail, the aforementioned three rotations were arranged with three levels of N fertilizer viz. recommended N, 75 and 50% of the recommended N in split plot design with three replications. Recommended rate of phosphorus fertilizer was applied for all treatments. Results indicated that faba bean and rapeseed wheat rotation increased wheat grain yield by 80% and 84 % cf. continuous wheat cropping, respectively. Rapeseed has been found better in controlling grass weed than faba bean. Demonstration of faba bean in the rotation enabled small-scale wheat farmers to use Rhizobium inoculants with appropriate inoculation techniques. Results of faba bean wheat rotation and fertilizer rate study indicated that there was no significant difference between wheat yields obtained from 100% and 75% recommended N fertilizer application. Hence, when faba bean wheat rotation is practiced 25% of the N fertilizer can be saved.

Pulses in Punjab: growth rate and decomposition analysis

Pulses are an important commodity group of crops that provides high quality protein supplementary cereal proteins for pre-dominantly large vegetarian population of Punjab. The state is known for its contribution of wheat and paddy to the national pool but it lags behind in production of pulses. Keeping this in view present study was undertaken to explore the status of pulses in Punjab with the computation of compound annual growth rate (CAGR) and decomposition analysis. For this purpose the secondary data from year 1985–86 to 2017–18 were taken. The results showed that the CAGR of area and production of total pulses in state showed a significantly negative growth of 6.13 and 5.60 per cent per annum respectively but positive growth (0.61%) was observed in case of yield. The decomposition analysis concluded that area effect (99.48%) was major contributing factor for change in production of total pulses followed by yield effect (3.87%). But interaction effect was found negative (−3.35%). Thus there is need to break the monoculture of wheat and paddy crops and regain the area under pulses by considering their invaluable benefits by providing improved varieties of seeds, pest resistant techniques, extension support, insurance coverage and sustained remunerative market for the produce of pulse growers.

Management of common root rot and Fusarium foot rot of wheat using Brassica carinata break crop green manure

Brassica crop rotations have been associated with the reduction of pathogens, due to both the production of volatile sulfur compounds and changes in soil microbial community composition. In this research Brassica carinata, as break crop green manure, was evaluated for the control of common root rot and Fusarium foot rot of durum wheat in a complete randomized experimental scheme. Field trials were performed on seven farms, in some of the most representative areas of cereal production in Sicily, from 2011 to 2013. A total eradication of Bipolaris sorokiniana and Microdochium nivale populations following the B. carinata break crop, as compared to wheat monoculture, was found in all experimental fields. Fusarium culmorum population reduction ranged between 90% and 66%, with an average of 82% considering all field trials data. Symptoms or signs of common root rot were absent on wheat plants grown after the B. carinata break crop but were detectable on the wheat monoculture. Both incidence and severity of Fusarium foot rot were also reduced, by an average of 40.6% and 56.3%, respectively, following the B. carinata break crop in six of the seven field trials. After B. carinata break crop, wheat plant growth showed significant increases in height and weight, with an average increase of 48.3% and 49.0% respectively. Durum wheat grain yield was also significantly greater following the Brassica green manure, with increases ranging from 9.5% to 62.2%, as compared to wheat monoculture. B. carinata break crop green manure was also characterized by interesting results in terms of disease management in comparison to controls. These results suggest that the use of Brassicas such as B. carinata, as a break crop green manure, may potentially provide significant reduction of pathogens and disease development as well as improvement in grain yield of the succeeding crop.

Effect of catch crops and tillage systems on some chemical properties of loess soil in a short-term monoculture of spring wheat

Effect of catch crops and tillage systems on some chemical properties of loess soil in a short-term monoculture of spring wheat

Intensifying crop rotations with pulse crops enhances system productivity and soil organic carbon in semi-arid environments

Pulse crops are commonly rotated with cereals to reduce nitrogen fertilizer use and increase economic returns while offering plant-based protein premium. However, it is unclear how pulse crops might affect soil quality, considering their low residue return to the soil. This study determined soil organic carbon, crop productivity, and system stability in intensified pulse-wheat (Triticum aestivum L.) rotations. Chickpea (Cicer arietinum L.)-wheat, lentil (Lens culinaris Medik.)-wheat, pea (Pisum sativum L.)-wheat, and wheat monoculture were studied over four cycles at two field sites. Across four rotation cycles, pea-wheat increased protein-based system yields by 22–82, 9–26 and 26–66% compared with chickpea-wheat, lentil-wheat, and wheat monoculture, respectively. Pea-wheat had the smallest variation in protein-based system yield and was most responsive to environments. Soil mineral N to the 60-cm depth was not different among the rotations involving pulse crops, but was higher than wheat monoculture. After eight years of rotations, soil organic carbon increased to 11.2 g kg−1 from the baseline soil of 10.3 g kg-1, but there was no difference among rotation systems. The integrated assessment of yield, soil organic carbon and system stability indicate that pulse crops-based rotations perform superior than wheat monoculture and pea-wheat system provides a paradigm of sustainable crop intensification.

Comparison of the Effect of Perennial Energy Crops and Arable Crops on Earthworm Populations

The purpose of the study was to compare earthworm communities under winter wheat in different crop production systems on arable land—organic (ORG), integrated (INT), conventional (CON), monoculture (MON)—and under perennial crops cultivated for energy purposes—willow (WIL), Virginia mallow (VIR), and miscanthus (MIS). Earthworm abundance, biomass, and species composition were assessed each spring and autumn in the years 2014–2016 using the method of soil blocks. The mean species number of earthworms was ordered in the following way: ORG > VIR > WIL > CON > INT > MIS > MON. Mean abundance of earthworms decreased in the following order: ORG > WIL > CON > VIR > INT > MIS > MON. There were significantly more species under winter wheat cultivated organically than under the integrated system (p = 0.045), miscanthus (p = 0.039), and wheat monoculture (p = 0.002). Earthworm abundance was significantly higher in the organic system compared to wheat monoculture (p = 0.001) and to miscanthus (p = 0.008). Among the tested energy crops, Virginia mallow created the best habitat for species richness and biomass due to the high amount of crop residues suitable for earthworms and was similar to the organic system. Differences in the composition of earthworm species in the soil under the compared agricultural systems were proven. Energy crops, except miscanthus, have been found to increase earthworm diversity, as they are good crops for landscape diversification.

Canola Breeding for HUMAN HEALTH

Canola Breeding for HUMAN HEALTH

Short-term plant legacy alters the resistance and resilience of soil microbial communities exposed to heat disturbance in a Mediterranean calcareous soil

Abstract Plant legacy is a concept representing the effects exerted by plants on soil once they are no longer growing. We hypothesized that plant species and mixture (intercropping) would induce different short-term legacy effects impacting carbon and nitrogen-related soil microbial activities and resistance and resilience after a heat disturbance. A microcosm experiment was conducted using a calcareous Mediterranean soil conditioned by a complete vegetative cycle in a greenhouse with four planting modalities (W = monoculture of Wheat (Triticum aestivum L.); L = monoculture of white Lupin (Lupinus albus L.); WL = both species intercropped; U = unplanted soil). Half of microcosms were incubated at 28 °C (C = control conditions) whereas the remaining half were exposed at 48 °C for 2 days (S = stress conditions), with an immediately return to control conditions. Microcosms were destructively sampled at 2, 7, 16 and 28 days (T2, T7, T16, T28) after the end of the heat disturbance and the following soil measurements were performed: Basal Respiration (BR), Substrate-Induced Respiration (SIR), Nitrification Enzyme Activity (NEA) and N mineral concentrations. Our results demonstrated that monocultures and intercropping promoted different legacy effects under control conditions especially for SIR. WL soils presented lower values of SIR than L and higher than W soils. For SIR, W and WL soils conferred greater resistance to the heat stress, whereas L and WL soils conferred higher resilience at T28. For NEA, no differences between soils were observed for resistance to heat stress, but at T16, soils having WL legacy were more resilient than L soils, but comparable to those having W legacy. Our results highlight that a short-term legacy effect is measurable but greatly differs between C- and N-related microbial activities. We estimated that intercropping had modified ability of soil microorganisms to face heat stress, suggesting that plant legacy effect has to be considered to mitigate extreme climatic events in Mediterranean soils.

Assessing soil quality indices based on soil organic carbon fractions in different long‐term wheat systems under semiarid conditions

AbstractThe literature shows a great number of soil quality indices (SQI) based on organic matter and its fractions. Our objectives were to determine the changes in soil organic carbon (SOC), carbon fractions and SQI in three production systems based on winter wheat (Triticum aestivum L.). The three production systems involved wheat monoculture under conventional tillage and no‐tillage (WWCT and WWNT, respectively) and traditional management, wheat under conventional tillage and grazing of natural grasses, alternated one year each (WGCT). In turn, each treatment was divided into N‐P‐fertilized (f) and non‐fertilized (nf). We analysed SOC, labile fractions and their ratios (SQI) at 0–5, 5–10 and 10–20 cm soil depths. SOC was significantly higher in WWNT‐f than in WWCT‐f and WGCT‐f at 0–5 and 0–20 cm range. Conversely, the lowest concentration was found in WWNT and WWCT in non‐fertilized plots. Particulate organic C (POC, 105–2,000 μm) was significantly affected by tillage at 0–5 cm with the greatest concentrations found in WWNT (mean = 3.2 g kg−1) followed by WGCT and WWCT (mean = 2.0 g kg−1). Soils under CT showed the lowest lability index (LI) values, whereas the conversion to NT increased it (0.74–1.28). Carbon management index (CMI) increased significantly at the 0–20 cm seven years after NT establishment compared to WWCT. SQI such as LI, CMI and SOC/silt+clay were more sensitive for differentiating production systems, whereas C pool index and C/N were more sensitive for differentiating the fertilizer application effect. Considering improvement in SQI and carbon fractions as indicators of better soil quality, adoption of NT improved the soil quality in the semiarid rainfed conditions in the short term.

Common and unique rhizosphere microbial communities of wheat and canola in a semiarid Mediterranean environment

In wheat (Triticum aestivum L.)-based cropping systems, rotation crops often provide a yield benefit to the following wheat crop. This has been documented for legume crops and canola (Brassica napus L.). In the present study, we examined bacterial and fungal communities in the rhizosphere of wheat and canola at six paired locations on fall and spring sampling dates using high-throughput sequencing of marker genes (bacterial 16S rRNA gene and fungal internal transcribed spacers). Soil type was the primary driver of both fungal and bacterial communities, with the communities of locations geographically closest, and with the same soil type, clustering together. Season (fall vs spring sampling) had the next strongest effect, followed by the crop species. Differences between the wheat and canola were more evident in the spring than in the fall. However, in contrast, bacterial and fungal species richness and diversity were not related to location or season, and instead were consistently higher in the rhizosphere of canola compared to wheat. Many bacterial groups were shared across both crop species, especially Janthinobacterium and Kaistobacter. Bacterial communities of wheat in the fall were dominated by Actinomycetes and Acidobacteria. But in the spring, these communities shifted to fast growing bacterial copiotrophs, including Pseudomonas, Janthinobacterium, Flavobacterium, Oxalobacteraceae, and Sphingobacteriaceae. Saprotrophic fungi such as Ulocladium, Mortierella, Cryptoccocus, Chaetomium, Penicillium and Trichoderma were also common to, and equally abundant in, the rhizosphere of both crops. Potential wheat root pathogens such as Thanatephorus (Rhizoctonia) Ceratobasidium, Oculimacula, Typhula, and Microdochium were more abundant in the wheat rhizosphere compared to canola. In conclusion, most of the communities of fungi and bacteria are not “host specific” but colonize the roots of both wheat and canola with differing relative abundance dependent on the season. A much smaller group of taxa were unique to the specific crop. This work provides novel insight into changes in crop rhizosphere communities when canola is introduced into dryland monoculture wheat cropping systems.

Soil Microbial Biomass and Fungi Reduced With Canola Introduced Into Long-Term Monoculture Wheat Rotations.

With increasing canola (Brassica napus L.) acreage in the Inland Pacific Northwest of the USA, we investigated the effect of this relatively new rotational crop on soil microbial communities and the performance of subsequent wheat (Triticum aestivum L.) crops. In a 6-year on-farm canola-wheat rotation study conducted near Davenport, WA, grain yields of spring wheat (SW) following winter canola (WC) were reduced an average of 17% compared to SW yields following winter wheat (WW). Using soil samples collected and analyzed every year from that study, the objective of this research was to determine the differences and similarities in the soil microbial communities associated with WC and WW, and if those differences were associated with SW yield response. Microbial biomass and community composition were determined using phospholipid fatty acid analysis (PLFA). The WC-associated microbial community contained significantly less fungi, mycorrhizae, and total microbial biomass than WW. Additionally, reduced fungal and mycorrhizal abundance in SW following WC suggests that the canola rotation effect can persist. A biocidal secondary metabolite of canola, isothiocyanate, may be a potential mechanism mediating the decline in soil microbial biomass. These results demonstrate the relationship between soil microbial community composition and crop productivity. Our data suggest that WC can have significant effects on soil microbial communities that ultimately drive microbially mediated soil processes.

Reduced tillage and increased residue retention increase enzyme activity and carbon and nitrogen concentrations in soil particle size fractions in a long-term field experiment on Loess Plateau in China

Soil organic matter (SOM) concentration and enzyme activity are important biochemical indicators of soil health for assessing the sustainability of agricultural management practices. However, little is known about the long-term effects of tillage and crop residue management on SOM and enzyme activities in soil particle-size fractions on the Loess Plateau of Northern China. The objective of this study was to investigate the effects of 11 years of combined tillage and crop residue management treatments on soil organic carbon (SOC), total nitrogen (TN) concentrations and enzyme activities in bulk soil and particle-size fractions from a rainfed wheat (Triticum aestivum L.) monoculture system in this region. We hypothesized that reduced tillage and increased residue retention would increase SOC, TN and enzyme activities in both bulk soil and particle-size fractions, and that enzyme activity would serve as a more sensitive indicator of soil health in response to management. Compared with conventional tillage and residue removal (CTRR), reduced tillage and stubble mulch residue retention (RTSM) increased bulk soil activities of most enzymes (sulfatase +68%, invertase +62%, β-glucosidase +58%, dehydrogenase +46%). These increases were greater than the relative increases in total SOC (34%) and TN (33%) concentrations, supporting our hypothesis of a stronger response in microbial activity to management than total element stocks. The RTSM treatment also increased SOC and TN concentrations, as well as β-glucosidase, acid phosphatase and urease activities in all particle-size fractions (2000-250, 250-53, 53-2 and < 2 μm) compared with the CTRR treatment. Both β-glucosidase and acid phosphatase showed a general decrease from coarse- to fine-sized fractions, and resembled the distribution of SOC and TN concentrations in particle-size fractions. Conversely, urease activity was greater in sand and clay fractions, which was decoupled from SOC and TN distributions. Our results indicate that biological indicators of soil health were more sensitive than C and N stocks to cumulative long-term changes in tillage and residue management.

Apricot-based agroforestry system in Southern Xinjiang Province of China: influence on yield and quality of intercropping wheat

Agroforestry is a common traditional practice in China, especially in Southern Xinjiang, Northwest China. However, the productivity of many agroforestry systems has been lower than expected in recent years. We chose an apricot (Prunus armeniaca L.)/wheat (Triticum aestivum L.) intercropping system to investigate the influence of apricot tree shade intensity on the grain yield and quality of intercropping wheat in Southern Xinjiang Province. We found that the mean daily light intensity in the east-row, inter-row, and west-row positions (apricot trees were planted in north–south orientation) in the intercropping systems decreased by 61.5%, 42.2%, and 63.6%, respectively, compared to the monoculture wheat. Correspondingly, the mean daily photosynthesis rate decreased by 52.0%, 28.4%, and 38.8%, respectively. The total florets, fertile florets, total spikelets, fertile spikelets, and grain yield and its components (including spike number, grains per spike, and thousand grain weight), and the total N and P contents of intercropping wheat in apricot-based intercropping systems were all significantly decreased compared to monoculture wheat. However, the protein content and wet gluten content of intercropped wheat were significantly increased compared to monoculture wheat. We did not find significant differences in any parameters among east-row, inter-row, and west-row positions in intercropping systems.