Wheat Biomass Research Articles

Evaluation of Hyperspectral Monitoring Model for Aboveground Dry Biomass of Winter Wheat by Using Multiple Factors

The aboveground dry biomass (AGDB) of winter wheat can reflect the growth and development of winter wheat. The rapid monitoring of AGDB by using hyperspectral technology is of great significance for obtaining the growth and development status of winter wheat in real time and promoting yield increase. This study analyzed the changes of AGDB based on a winter wheat irrigation experiment. At the same time, the AGDB and canopy hyperspectral reflectance of winter wheat were obtained. The effect of spectral preprocessing algorithms such as reciprocal logarithm (Lg), multiple scattering correction (MSC), standardized normal variate (SNV), first derivative (FD), and second derivative (SD); sample division methods such as the concentration gradient method (CG), the Kennard–Stone method (KS), and the sample subset partition based on the joint X–Y distances method (SPXY); sample division ratios such as 1:1 (Ratio1), 3:2 (Ratio2), 2:1 (Ratio3), 5:2 (Ratio4), and 3:1 (Ratio5); dimension reduction algorithms such as uninformative variable elimination (UVE); and modeling algorithms such as partial least-squares regression (PLSR), stepwise multiple linear regression (SMLR), artificial neural network (ANN), and support vector machine (SVM) on the hyperspectral monitoring model of winter wheat AGDB was studied. The results showed that irrigation can improve the AGDB and canopy spectral reflectance of winter wheat. The spectral preprocessing algorithm can change the original spectral curve and improve the correlation between the original spectrum and the AGDB of winter wheat and screen out the bands of 1400 nm, 1479 nm, 1083 nm, 741 nm, 797 nm, and 486 nm, which have a high correlation with AGDB. The calibration sets and validation sets divided by different sample division methods and sample division ratios have different data-distribution characteristics. The UVE method can obviously eliminate some bands in the full-spectrum band. SVM is the best modeling algorithm. According to the universality of data, the better sample division method, sample division ratio, and modeling algorithm are SPXY, Ratio4, and SVM, respectively. Combined with the original spectrum and by using UVE to screen bands, a model with stable performance and high accuracy can be obtained. According to the particularity of data, the best model in this study is FD-CG-Ratio4-Full-SVM, for which the R2c, RMSEc, R2v, RMSEv, and RPD are 0.9487, 0.1663 kg·m−2, 0.7335, 0.3600 kg·m−2, and 1.9226, respectively, which can realize hyperspectral monitoring of winter wheat AGDB. This study can provide a reference for the rational irrigation of winter wheat in the field and provide a theoretical basis for monitoring the AGDB of winter wheat by using hyperspectral remote sensing technology.

Different responses of agroecosystem greenhouse gas emissions to tillage practices in a Chinese wheat–maize cropping system

To mitigate greenhouse gas (GHG) emissions of intensified agriculture, conservation practices are gradually being implemented in Chinese wheat–maize cropping systems. However, the effects of different tillage practices on agricultural field GHG emissions and subsequent global warming potential (GWP) are poorly documented. In this study, a three-year field experiment was conducted from 2019 to 2021 to assess the effects of tillage on the emissions of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and eventually GWP. Compared to conventional tillage (CT), no-tillage (NT) significantly decreased CO2, CH4, and N2O emissions by 35.43%, 67.33%, 339.07%, respectively, which resulted in a decrease of 37.25% in GWP during three annual cycles. Based on the results of this study, soil could potentially act as a net source of CO2 and CH4 under both CT and NT, and a net sink of N2O under NT. Annually, non-growing season contributed 16.9%, 15.6%, and 13.8% soil CO2, CH4, and N2O fluxes, and 16.6% GWP under CT and 17.3%, 16.4%, 21.6%, and 17.3% under NT, respectively. Compared to CT, NT improved the aboveground biomass and grain yields of wheat by 21.3% and 13.3% from averaged results, respectively; no significant differences were found for maize yields. Although principal component analysis showed that soil temperature had higher correlations with CO2 emissions and GWP as compared to soil moisture, soil moisture affected GHG emissions more than soil temperature as demonstrated by the structural equation model. The modeling analysis found that NT increased soil moisture, pH, and bulk density, thus increasing soil organic carbon and decreasing total nitrogen content, eventually inhibiting GHG emissions. This research demonstrated that NT had the potential to mitigate GHG emissions, yet stability needed further investigation on long-term scales.∙Graphical

Availability Changes in Different Exogenous Selenium Fertilizers in Soil and Their Effects on Selenium Accumulation in Wheat

In order to understand the differences in the uptake and accumulation of several common exogenous selenium fertilizers by crops, a wheat pot experiment was conducted to study the availability changes in different selenium fertilizers (potassium selenate, potassium selenite, EDTA-chelated selenium, selenium powder, fly ash, and selenium-enriched straw) in soil and their effects on wheat growth and selenium uptake and distribution. The results showed that the change in availability of different exogenous selenium types in soil was different. During the whole growth period of wheat, the soil available selenium proportion of selenate, selenite, and EDTA-chelated selenium treatment was significantly higher than that of the control (CK), respectively, but there was no significant difference between the other treatments and the CK treatment. In the early stage of wheat growth, the soil available selenium proportion of selenate, selenite, and selenium powder treatment decreased gradually and tended to be stable in the later growth stage of wheat; however, the soil available selenium proportion of other exogenous selenium treatments showed a dynamic change of decreasing in the early period and increasing in the late period. The available selenium content in soil significantly affected the selenium uptake by wheat, and there was a significant positive correlation between them. Selenate application significantly increased the grain and leaf biomass of wheat, but other selenium fertilizers had no significant effect on wheat growth. The accumulation capacity of different exogenous selenium fertilizers for wheat followed the order of selenate>selenite, EDTA-chelated selenium>selenium powder, fly ash, and selenium-enriched straw. There was no significant difference between the selenium powder, fly ash, and selenium-enriched straw treatments and the CK treatment. Selenium was more easily transferred to and accumulated in the stems and leaves of wheat after the application of selenate, whereas selenium was more easily transferred to and accumulated in grains after the application of selenite and EDTA-chelated selenium.

Enhanced soil water recovery and crop yield following conversion of 9-year-old leguminous pastures into croplands

Pasture-crop rotation has been considered as an efficient agronomical practice to improve soil and water conservation, develop livestock production, and promote food security. However, the characteristics of soil water restoration and performances of crop yield and water use efficiency (WUE) after conversion of long-term leguminous pasture into croplands still remain unclear. A field experiment was conducted in China’s Loess Plateau to investigate soil water restoration and wheat yields in crop rotation with Italian ryegrass (Festuca perennis Lam.) and winter wheat (Triticum aestivum L.) converted from three 9-year-old leguminous pastures, viz. milk vetch (Astragalus adsurgens Pall.), alfalfa (Medicago sativa L.) and bush clover (Lespedeza davurica S.), and unplanted control (fallow). Soil water in the alfalfa treatment gradually recovered from up to down compared to the fallow treatment (control) during cultivation phase. After one year of rotation, the recovery levels of soil water in the three pasture-crop rotation systems at 0–500 cm soil depth were 97.1%, 95.5% and 94.2%, respectively, compared to the fallow treatment. The legume treatments significantly enhanced the crop yield (35.6%−64.5%), aboveground biomass (28.7%−59.4%) and WUE (60%−68.3%) of winter wheat compared with fallow. These results imply that the concerns about soil desiccation from long-term alfalfa was resolvable after long-term alfalfa converted into cropland in the rainfed farming area of Loess Plateau. The results also suggest that legume pasture-crop rotation can facilitate achieving a sustainable development of rainfed farming.

The Effect of Nitrogen Supply on Water and Nitrogen Use Efficiency by Wheat–Chickpea Intercropping System under Rain-Fed Mediterranean Conditions

It is well known that legume–cereal intercropping systems are more efficient in terms of resources use, in particular nitrogen (N) and water. However, the response of this cropping system to water and N co-limitation was poorly studied in most of the recent field researches. The present study aims to assess the relationship between N and water use efficiency (NUE and WUE) by chickpea–durum wheat intercropping under contrasted climate and N supply conditions. Field experiments were carried out during the 2021/2022 growing season, in three sites located at both sub-humid and semi-arid regions. WUE, NUE, aboveground biomass, grain yield and crop physiological parameters for either intercropped chickpea or durum wheat were assessed and compared to the respective measurements in monocultures among all N-fertilizer level × site treatments. The results showed that WUE relative to grain yield (WUEGY) and biomass (WUEYB) were significantly higher in sole cropped wheat under the conditions of the three studied sites, except for WUEYB in S2, in which intercropping increased WUEYB by +0.46 and +1.03 kg m−3, as compared respectively, to monoculture under low application of N fertilizer. As compared to chickpea monoculture, intercropping increased WUEGY by more than 0.30 and 0.57 kg m−3 under semi-arid conditions (S1 and S3) over three N-application doses, and by more than 0.18 kg m−3 under sub-humid conditions (S2). Simultaneously, NUE was significantly increased by intercropping, where in the mixed crop the highest values were noted as compared to sole-cropped durum wheat and chickpea. However, reducing the N-application dose leads to a gradual increase in NUE by more than 4.44 kg kg−1. As a consequence, intercropping enhanced protein accumulation in the grain yield of mixed crops by more than 30 kg ha−1 as compared to sole-cropped durum wheat, in particular under moderate N-application and sub-humid climate. Indeed, average chlorophyll content was increased (7.8%) in intercropped durum wheat under all applied N-doses in sub-humid conditions. Rain-fed chickpea–wheat intercropping promotes an improvement in growth and yield quality thanks to simultaneous optimization of water and N use under low and moderate N-application in both semi-arid and sub-humid climates.

Influence of decomposition agent application and schedule in wheat straw return practice on soil quality and crop yield

Straw return is a beneficial agricultural practice but mechanisms and information on microbial community alterations initiated by decomposed straw and promotion of soil nutritive content and conservation is still not adequately understood. Therefore, the study applied molecular, bioinformatics, chemical and plant yield analysis to determine the effect of wheat straw return and decomposing agent on soil, fungi and crop yield characteristics under wheat biomass return with and without the inclusion of the decomposition agent at varying times. We hypothesized no difference in fungal community diversity and composition, no changes in soil characteristics as well as no changes in cotton growth characteristics between three different conditions (i) no straw return, (ii) straw return under decomposition agent and (iii) straw return under no decomposition agent. It involved analysis of changes in fungal community diversity and composition, changes in soil characteristics as well as changes in cotton growth characteristics under the different treatments. The phyla Ascomycota and Basidiomycota were in relatively in highest abundance within the straw return under decomposition agent treatment than in both the straw return treatment and straw return under no decomposition agent treatment. The pathogenic genus Aspergillus as the most dominant under no straw return treatment, while genus Trechispora, Lulwaona and Dioszegia were most dominant under straw return under no decomposition agent treatment. Indeed, there was high fungal community dissimilarity between the three treatments. Additionally, there was increased rise in fungal diversity, soil nutrients and crop yield under the straw return within the shortest possible time, and the addition of decomposing agent further enhanced the high fungal species diversity.Graphical

Microbial activity and hard red spring wheat growth improvement following biostimulant application

AbstractReclamation of oil and gas disturbed soils is challenging due to diminished function (i.e., soil physical, chemical, and biological properties) from the loss of soil organic carbon (SOC) and potential mixing of topsoil and subsoil. Biostimulants are agro‐products applied to soil to improve SOC formation, microbial nutrient cycling, and crop yields, suggesting their potential use in reclaiming oil and gas disturbed soils. However, studies on the ability of biostimulants to enhance reclamation in disturbed soils are limited. Therefore, research was conducted to determine if biological properties were affected by biostimulant products in soil collected from an active pipeline installation project. The study was conducted in a greenhouse using pots consisting of the following soil treatments: TS100 (100% topsoil), TS50 (1:1 by‐weight subsoil/topsoil), TS25 (3:1 subsoil/topsoil), TS12.5 (7:1 subsoil/topsoil), and TS0 (100% subsoil). Blended soil either received a liquid inoculant or biotic mulch biostimulant and were planted with hard red spring wheat (Triticum aestivum) later on. Soil biological properties were generally influenced by topsoil concentration where TS50 consistently produced similar results to TS100, however, nitrogen (N) and phosphorus (P) were also influenced by biostimulant treatment. Additionally, wheat biomass was significantly greater in the liquid treatment, whereas the biotic mulch stimulated greater microbial abundance and activity. Overall, increased topsoil improved biological recovery in the short term, and the addition of biostimulants in blended soils can also enhance recovery regardless of topsoil content. However, it is unclear whether the recovery is sustained into the long‐term without additional biostimulant application.

WHEAT BIOMASS ESTIMATION FROM UAV IMAGERY USING AN ENSEMBLE LEARNING APPROACH WITH BAYESIAN OPTIMIZATION

Abstract. Wheat is one of the most important food supply and food security globally, especially in developing countries. Therefore, predicting the performance and determining the factors that affect the production of this product is very important. Biomass is one of the crop’s most important biophysical parameters, and its correct estimation can help improve accurate monitoring of growth and crop performance forecasting. With the recent advances in remote sensing, access to aerial images taken by unmanned aerial vehicles (UAV) for monitoring crops has been provided. This study investigates the potential of visible UAV images and the resulting vegetation indices to estimate the dry biomass of two types of Brazilian wheat. For this purpose, the performance of three regression algorithms, including Random Forest (RF), eXtreme Gradient Boosting (XGB), and Gradient Boosting Machine (GBM), to estimate wheat biomass was evaluated. Also, to improve the performance of regression models, Bayesian optimization (BO) was used to adjust the Hyper-parameters, and random forest feature selection was used to select the optimal subset of features. Based on the results, the XGB algorithm with the Root Mean Square Error (RMSE) of about 911.86 (Kg/ha) and coefficient of determination (R2) of about 0.89% showed better performance in biomass estimation than other algorithms.

Effects of microplastics and cadmium on the soil-wheat system as single and combined contaminants

Two types of microplastics (MPs) (micro polyethylene (mPE) and micro polypropylene (mPP)) were studied alongside and cadmium (Cd) to determine how they affected soil-wheat systems, both individually and in mixed combinations. This was accomplished by carrying out a pot experiment to reveal their respective interaction effects. Results showed that in different Cd pollution levels soils (0, 1, and 5 mg kg−1), chlorophyll concentrations in wheat leaves decreased markedly with rising levels of mPE/mPP. In the single mPE treatment, as the mPE content in the soil increased, the aboveground and root biomass improved. By contrast, in the single mPP treatment, when the mPP content was low, the aboveground biomass of wheat increased and with the mPP content increased, the aboveground biomass of wheat decreased. This result was also shown in the combined contamination of mPE/mPP and Cd (1 mg kg−1) in the root biomass. With an increase in Cd concentration (that is, at 5 mg kg−1) in the combined contamination, this phenomenon continued in the aboveground biomass while in the roots, there was a promotion effect. At Cd contaminated soil (1 mg kg−1), MPs inhibited Cd enrichment in aboveground wheat, but at 5 mg kg−1, Cd enrichment was promoted instead, in both aboveground and roots. Adding mPE/mPP diminished pH and the Cd effective state concentration in soil. The combined contamination of mPE/mPP and Cd affected the Cd biological enrichment in the wheat to some extent, which was influenced by the types of MP and pollution levels of Cd in the soil.

Combined effects of biochar and plant growth promoting bacteria Pseudomonas putida TSAU1 on plant growth, nutrient uptake of wheat, and soil enzyme activities

Many studies indicate the favorable effect of biochar on soil quality and plant fitness. A few studies on the biochar interactions with rhizosphere bacteria and their impact on plant development and nutrient acquisition have been reported. In this study, pot experiments in a glasshouse were performed to figure out the interactive effect of plant beneficial bacteria Pseudomonas putida TSAU6 and biochar amendment on the wheat (Triticum aestivum L.) growth, nutrient uptake, and soil biological activity. The results demonstrated that root and shoot dry biomass of wheat grown in soil mixed with biochar and combined with P. putida TSAU1 were enhanced significantly compared to the control plants. The nitrogen (N) and phosphorus (P) content in plant biomass were affected by biochar addition and biochar combined with a bacterial inoculant. It was also observed a change in soil enzyme activities, where higher fluorescein diacetate (FDA) and protease activities were observed after biochar application compared to control soil. The addition of biochar combined with bacterial inoculant showed a more profound effect on wheat growth and N, P acquisition. This positive effect is also associated with soil enzyme activities that are involved directly or indirectly in the N and P cycle. These findings confirm the potential of microbial inoculants induced by biochar to improve wheat production.

UAV Flight Height Impacts on Wheat Biomass Estimation via Machine and Deep Learning

UAV Flight Height Impacts on Wheat Biomass Estimation via Machine and Deep Learning

An assessment of the efficacy of biochar and zero-valent iron nanoparticles in reducing lead toxicity in wheat (Triticum aestivum L.).

Soil heavy metal contamination is increasing rapidly due to increased anthropogenic activities. Lead (Pb) is a well-known human carcinogen causing toxic effects on humans and the environment. Its accumulation in food crops is a serious hazard to food security. Developing environment-friendly and cost-efficient techniques is necessary for Pb immobilization in the soil. A pot experiment was executed to determine the role of biochar (BC), zero-valent iron nanoparticles (n-ZVI), and zero-valent iron nanoparticles biochar composite (n-ZVI-BC) in controlling the Pb mobility and bioaccumulation in wheat (Triticum aestivum L.). The results showed that BC and n-ZVI significantly enhanced the wheat growth by increasing their photosynthetic and enzymatic activities. Among all the applied treatments, the maximum significant (p ≤ 0.05) improvement in wheat biomass was with the n-ZVI-BC application (T3). Compared to the control, the biomass of wheat roots, shoots & grains increased by 92.5, 58.8, and 49.1%, respectively. Moreover, the soil addition of T3 amendment minimized the Pb distribution in wheat roots, shoots, and grains by 33.8, 26.8, and 16.2%, respectively. The outcomes of this experiment showed that in comparison to control treatment plants, soil amendment with n-ZVI-BC (T3) increased the catalase (CAT), superoxide dismutase (SOD) activity by 49.8 and 31.1%, respectively, ultimately declining electrolyte leakage (EL), malondialdehyde (MDA) and hydrogen peroxide (H2O2) content in wheat by 38.7, 33.3, and 38%respectively. In addition, applied amendments declined the Pb mobility in the soil by increasing the residual Pb fractions. Soil amendment with n-ZVI-BC also increased the soil catalase (CAT), urease (UR), and acid phosphatase (ACP) activities by 68, 59, and 74%, respectively. Our research results provided valuable insight for the remediation of Pb toxicity in wheat. Hence, we can infer from our findings that n-ZVI-BC can be considered a propitious, environment friendly and affordable technique for mitigating Pb toxicity in wheat crop and reclamation of Pb polluted soils.

The effect of conventional and sustainable agricultural management practices on carbon and water fluxes in a Mexican semi-arid region.

Agriculture is essential for food security. However, conventional agriculture alters the water and carbon cycle and soil properties. We investigated the effect of conventional management (CM) and sustainable management (SM) on the carbon and water cycle in crops of nopal (Np) and wheat (Wh). A micrometeorological eddy covariance tower was installed to measure water use through evapotranspiration (ET) and the net exchange of CO2 during the crop's development. Gross primary productivity (GPP), water use efficiency (WUE), and soil properties were obtained. The results showed that both agricultural managements influenced the carbon flux of the ecosystem, with a lower GPP and Reco in the nopal field (1.85 and 0.99 mmol C m-2 s-1, respectively), compared to the wheat field (6.34 and 1.8 mmol C m-2 s-1, respectively). It was mainly attributed to the metabolic plant differences, phenological stages, and wheat biomass developed during the winter. On the other hand, the accumulated ET in the SM-Wh plots was lower than SM-Np. Therefore, the crops subjected to sustainable practices use water more efficiently with 1.42 and 1.03 g C m-3 H2O for nopal and wheat, respectively. In regard to soil properties, it was observed that tillage alters microbial activity affecting organic matter and carbon. It can be concluded that the differences in agricultural management for both crops altered the carbon and water cycle and soil quality. In addition, implementing good agricultural practices allows more efficient use of water by the plant, higher retention of water in the soil, and less ET.

Effects of biochar and arbuscular mycorrhizal fungi on winter wheat growth and soil N2O emissions in different phosphorus environments.

Promoting crop growth and regulating denitrification process are two main ways to reduce soil N2O emissions in agricultural systems. However, how biochar and arbuscular mycorrhizal fungi (AMF) can regulate crop growth and denitrification in soils with different phosphorus (P) supplies to influence N2O emission remains largely unknown. Here, an eight-week greenhouse and one-year field experiments biochar and/or AMF (only in greenhouse experiment) additions under low and high P environments were conducted to characterize the effects on wheat (Triticum aestivum L.) growth and N2O emission. With low P supply, AMF addition decreased leaf Mn concentration (indicates carboxylate-releasing P-acquisition strategies), whereas biochar addition increased leaf Mn concentration, suggesting biochar and AMF addition regulated root morphological and physiological traits to capture P. Compared with low P supply, the high P significantly promoted wheat growth (by 16-34%), nutrient content (by 33-218%) and yield (by 33-41%), but suppressed soil N2O emissions (by 32-95%). Biochar and/or AMF addition exhibited either no or negative effects on wheat biomass and nutrient content in greenhouse, and biochar addition promoted wheat yield only under high P environment in field. However, biochar and/or AMF addition decreased soil N2O emissions by 24-93% and 32% in greenhouse and field experiments, respectively. This decrease was associated mainly with the diminished abundance of N2O-producing denitrifiers (nirK and nirS types, by 17-59%, respectively) and the increased abundance of N2O-consuming denitrifiers (nosZ type, by 35-65%), and also with the increased wheat nutrient content, yield and leaf Mn concentration. These findings suggest that strengthening the plant-soil-microbe interactions can mitigate soil N2O emissions via manipulating plant nutrient acquisition and soil denitrification.

Modeling management of continuous dryland cotton with an intervening winter wheat cover crop in a semiarid climate

Although winter cover crop residue can mitigate the stresses of dryland production in semi-arid regions, cover crops can also reduce soil moisture and cash crop yields. In some field studies of dryland cotton grown after terminated winter wheat in the U.S. Southern High Plains (SHP) and Texas Rolling Plains cotton yields were increased relative to continuous cotton, while others had no significant yield or soil water effect. These uncertain outcomes may be due to the trial's limited sampling of seasonal rainfall conditions. To estimate the probabilities of cover crop effects under more representative SHP climate conditions, 294 station-years of crop model simulations of terminated winter wheat followed by dryland cotton were conducted. These simulations were driven by weather data from 21 SHP weather stations during 2005–2019. Each station-year's simulations were repeated under 54 combinations of wheat planting, termination, and cotton planting dates, 2 soil series with different water capacities, and 10 initial soil moisture conditions. When simulations begin with fall soil moisture at field capacity optimal management options for both soils plant wheat early and cotton late, but have different wheat termination dates. Before cotton planting winter cover crop effects are dominated by reduced surface evaporation and increased transpiration, with greater transpiration effects producing decreased column soil moisture (CSM) at wheat termination. Some soil moisture recharge occurs between termination and cotton planting, but cover crops reduce CSM at cotton planting in both soils in ~75% of simulations. Reduced soil evaporation and soil moisture recovery continues after cotton planting, resulting in positive effects on seed cotton yield in 50% of the silty clay loam simulations and in 67% of the fine sandy loam simulations. Gradually reducing initial fall soil moisture in the silty clay loam reduces wheat biomass but increases the incidence of positive effects on seed cotton yields and CSM at cotton planting and harvest. By contrast, drier initial soil moisture in the fine sandy loam had relatively minor yield and CSM effects. In both soils terminated wheat residue led to increased CSM at cotton harvest in at least 70% of the simulations regardless of soil moisture at wheat planting.

Nematodes and their bacterial prey improve phosphorus acquisition by wheat.

Plant growth is greatly influenced by the rhizosphere microbiome, which has been traditionally investigated from a bottom-up perspective assessing how resources such as root exudates stimulate microbial growth and drive microbiome assembly. However, the importance of predation as top-down force on the soil microbiome remains largely underestimated. Here, we planted wheat both in natural and in sterilized soils inoculated with the key microbiome predators - bacterivorous nematodes - to assess how plant performance responds to top-down predation of the soil microbiome and specific plant growth-promoting bacteria, namely phosphate-solubilizing bacteria. We found that nematodes enriched certain groups (e.g. Actinobacteria, Chloroflexi, and Firmicutes) and strengthened microbial connectance (e.g. Actinobacteria and Proteobacteria). These changes in microbiome structure were associated with phosphate-solubilizing bacteria that facilitated phosphorus (P) cycling, leading to greater P uptake and biomass of wheat in both soils. However, the enhancement varied between nematode species, which may be attributed to the divergence of feeding behavior, as nematodes with weaker grazing intensity supported greater abundance of phosphate-solubilizing bacteria and better plant performance compared with nematodes with greater grazing intensity. These results confirmed the ecological importance of soil nematodes for ecosystem functions via microbial co-occurrence networks and suggested that the predation strength of nematodes determines the soil bacteria contribution to P biogeochemical cycling and plant growth.

Effective utilization of weak alkaline soils with Cd-contamination by wheat and rape intercropping

Recently, there has been increasing concern about the health hazards of heavy metal-polluted farmlands. Recent findings suggest that intercropping could be effective remediation strategy for agricultural soils without affecting crop biomass yield. However, there are concerns on the heavy metal accumulation in plant organs in phytoremediation, emphasizing the need to develop an effective intercropping remediation model. In this study, we evaluated the effects of intercropping rape and wheat with different accumulation characteristics of cadmium (Cd), and crop growth and physiological characteristics. Intercropping significantly reduced the Cd content of rape shoot and root, with the rape–low Cd-accumulating wheat intercropping system yielding the best results. However, intercropping had no significant effect on Cd accumulation in wheat. Additionally, intercropping affected the root system configuration and structure, photosynthetic indicators, chlorophyll content, crop enzyme content, and rhizosphere enzyme activity of both species, but did not significantly affect the biomass of wheat and rape. Overall, our findings showed that intercropping rape with a low Cd-accumulating wheat variety could be an effective model for safe production of wheat and rape in weak alkaline soils without compromising biomass yield. The study demonstrates that similar innovative, effective, and judicious intercropping strategy can enrich the theory of contaminated soil remediation.

Nitrogen Mitigates Salt Stress and Promotes Wheat Growth in the Yellow River Delta, China

Salt-affected soils is an important soil resource. Understanding fertilizer and salinity interaction are of great economic importance for improving crop yield and fertilizer use efficiency. A pot experiment was carried out to study the application of nitrogen (N) for ameliorating salt stress in wheat grown in the coastal saline soil of the Yellow River delta. Several controlling levels of salinity and nitrogen (0.7, 1.7, 2.7 g/kg, and 135, 270, and 405 kg/ha) were designed in a pot experiment in a stable water content state to investigate the N and salt interaction on soil properties and winter wheat growth characteristics. The results showed that the dry weight of winter wheat was promoted by salinity in the early growth stage (20 days), then it was gradually inhibited by nitrogen fertilizer. When winter wheat was grown by 54 days, the N and salinity had significant effects on the biomass of winter wheat. The nitrogen content of wheat shoot and root was mainly affected by N addition usage, and the largest value was obtained in 270 kg/ha N dosage treatments. The higher the salt content existed in the soil, the lower the growth rate shown in wheat cultivation. Under saline conditions, the N fertilizer application amount should be controlled to no more than 270 kg/ha, so that it could greatly promote wheat growth. Reasonable fertilizer usage could significantly contribute to crop yield and food quality of the saline agriculture in the Yellow River delta.

Intercropping with herbs minimizes cadmium availability through altering physicochemical dynamics and metabolite profiles in wheat rhizosphere

AbstractFor the past few years, the production of safe crops in Cd‐contaminated soil has attracted more and more attention, and the intercropping of wheat and herbaceous plants has gradually become an effective way. However, how the physicochemical and metabolic processes because of the intercropping change Cd availability are still unclear. In this study, we studied the influence of changes in soil physicochemical properties induced by intercropping of wheat with different herbs on soil Cd availability of Cd. Meanwhile, we innovatively studied the effect of intercropping on rhizosphere metabolites and evaluated the impact on Cd transfer. Results showed that the highest wheat biomass was presented in the intercropping system with the Cichorium intybus L. (W4) and Aus hypochondriacus L. (W5) increasing by 57.66% and 54.05% individually, compared with monocropping, while W1, W2, and W3 increasing slightly. Further, the Cd accumulation in wheat grains under W4 and W5 treatment decreased by 44.95% and 43.12%, respectively. Structural equation model confirmed that the increased pH, CEC contributed to the decreased Cd availability in soil, as well the changed metabolic profiles in wheat rhizosphere after intercropping. Specially, up‐regulation of fatty acid metabolism allowed wheat plants to maintain a normal intracellular environment under stress conditions. Similarly, up‐regulation of saccharide and amino acid metabolism induced the accumulation of sugars and proteins, which positively increased wheat biomass and Cd‐binding proteins, thus inhibiting the migration of soil Cd into wheat tissue. Collectively, this study provided reasonable insights towards understanding the metabolic mechanisms how intercropping altered Cd availability.

Application and Evaluation of a Simple Crop Modelling Framework: A Case Study for Spring Barley, Winter Wheat and Winter Oilseed Rape over Ireland

Globally, croplands represent a significant contributor to climate change, through both greenhouse gas emissions and land use changes associated with cropland expansion. They also represent locations with significant potential to contribute to mitigating climate change through alternative land use management practices that lead to increased soil carbon sequestration. In spite of their global importance, there is a relative paucity of tools available to support field- or farm-level crop land decision making that could inform more effective climate mitigation practices. In recognition of this shortcoming, the Simple Algorithm for Yield Estimate (SAFY) model was developed to estimate crop growth, biomass, and yield at a range of scales from field to region. While the original SAFY model was developed and evaluated for winter wheat in Morocco, a key advantage to utilizing SAFY is that it presents a modular architecture which can be readily adapted. This has led to numerous modifications and alterations of specific modules which enable the model to be refined for new crops and locations. Here, we adapted the SAFY model for use with spring barley, winter wheat and winter oilseed rape at selected sites in Ireland. These crops were chosen as they represent the dominant crop types grown in Ireland. We modified the soil–water balance and carbon modules in SAFY to simulate components of water and carbon budgets in addition to crop growth and production. Results from the modified model were evaluated against available in situ data collected from previous studies. Spring barley biomass was estimated with high accuracy (R2 = 0.97, RMSE = 95.8 g·m−2, RRMSE = 11.7%) in comparison to GAI (R2 = 0.73, RMSE = 0.44 m2·m−2, RRMSE = 10.6%), across the three years for which the in situ data was available (2011–2013). The winter wheat module was evaluated against measured biomass and yield data obtained for the period 2013–2015 and from three sites located across Ireland. While the model was found to be capable of simulating winter wheat biomass (R2 = 0.71, RMSE = 1.81 t·ha−1, RRMSE = 8.0%), the model was found to be less capable of reproducing the associated yields (R2 = 0.09, RMSE = 2.3 t·ha−1, RRMSE = 18.6%). In spite of the low R2 obtained for yield, the simulated crop growth stage 61 (GS61) closely matched those observed in field data. Finally, winter oilseed rape (WOSR) was evaluated against a single growing season for which in situ data was available. WOSR biomass was also simulated with high accuracy (R2 = 0.99 and RMSE = 0.52 t·ha−1) in comparison to GAI (R2 = 0.3 and RMSE = 0.98 m2·m−2). In terms of the carbon fluxes, the model was found to be capable of estimating heterotrophic respiration (R2 = 0.52 and RMSE = 0.28 g·C·m−2·day−1), but less so the ecosystem respiration (R2 = 0.18 and RMSE = 1.01 g·C·m−2·day−1). Overall, the results indicate that the modified model can simulate GAI and biomass, for the chosen crops for which data were available, and yield, for winter wheat. However, the simulations of the carbon budgets and water budgets need to be further evaluated—a key limitation here was the lack of available in situ data. Another challenge is how to address the issue of parameter specification; in spite of the fact that the model has only six variable crop-related parameters, these need to be calibrated prior to application (e.g., date of emergence, effective light use efficiency etc.). While existing published values can be readily employed in the model, the availability of regionally derived values would likely lead to model improvements. This limitation could be overcome through the integration of available remote sensing data using a data assimilation procedure within the model to update the initial parameter values and adjust model estimates during the simulation.