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Field Crops Research
Elsevier
Field Crops Research

Elsevier

0378-4290

Field Crops Research/Journal Field Crops ResearchSCIISTP
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    An assessment of background removal approaches for improved estimation of rice leaf nitrogen concentration with unmanned aerial vehicle multispectral imagery at various observation times

    Zhu Y.Cao W.Cheng T.Wang W....
    14页
    查看更多>>摘要：? 2022 Elsevier B.V.Background effect is a crucial limitation for the monitoring of leaf nitrogen concentration (LNC) in crops with unmanned aerial vehicle (UAV) multispectral imagery. Some background removal approaches have been developed for improve the estimation of LNC, but their performances are not compared in one study and it is unclear whether they are sensitive to the observation time of UAV imagery. This study evaluated three background removal approaches, i.e., the soil-adjusted vegetation index (SAVI) approach, the green pixel vegetation index approach (GPVI) and abundance adjusted vegetation index (AAVI), for estimating rice LNC from UAV-based multispectral imagery at individual and across growth stages as well as different observation times of the day. The red edge chlorophyll index (CIre) was chosen as the common basis for the last two approaches. In particular, the AAVI approach was refined with a higher number of endmembers and automated endmember extraction, and further evaluated for assessing the effect of separating sunlit components from shaded components of the canopy. Our results demonstrated that the vegetation indices (VIs) for off-noon observation times showed better relationships with LNC than those for noon at individual and across growth stages. Compared to both SAVI and CIre-green, the AACIre for all pixels (AACIre-all) exhibited the weakest sensitivity to observation time and yielded the best relationships for single-stage (jointing: r2=0.70, booting: r2=0.76, heading: r2=0.70) and across-stage (r2=0.66) models. Among the AAVIs derived from three categories of pixels, the AACIre-sunlit (R2 =0.90, RMSE=0.17%, Bias=0.03%) outperformed AACIre-all (R2 =0.85, RMSE=0.23%, Bias=0.08%) and then AACIre-shaded (R2 =0.38, RMSE=0.49%, Bias=0.40%) remarkably for the estimation accuracy of LNC. This study suggests that the refined AAVI approach has great value in reducing the background effect for more accurate monitoring of growth parameters and could be extended to other crops and regions for improved precision crop management and field-based high-throughput phenotyping.
      原文链接:
    • NSTL
    • Elsevier

    Biological nitrogen fixation and prospects for ecological intensification in cereal-based cropping systems

    Ladha J.K.Bennett A.Peoples M.B.Reddy P.M....
    34页
    查看更多>>摘要：? 2022The demand for nitrogen (N) for crop production increased rapidly from the middle of the twentieth century and is predicted to at least double by 2050 to satisfy the on-going improvements in productivity of major food crops such as wheat, rice and maize that underpin the staple diet of most of the world's population. The increased demand will need to be fulfilled by the two main sources of N supply – biological nitrogen (gas) (N2) fixation (BNF) and fertilizer N supplied through the Haber-Bosch processes. BNF provides many functional benefits for agroecosystems. It is a vital mechanism for replenishing the reservoirs of soil organic N and improving the availability of soil N to support crop growth while also assisting in efforts to lower negative environmental externalities than fertilizer N. In cereal-based cropping systems, legumes in symbiosis with rhizobia contribute the largest BNF input; however, diazotrophs involved in non-symbiotic associations with plants or present as free-living N2-fixers are ubiquitous and also provide an additional source of fixed N. This review presents the current knowledge of BNF by free-living, non-symbiotic and symbiotic diazotrophs in the global N cycle, examines global and regional estimates of contributions of BNF, and discusses possible strategies to enhance BNF for the prospective benefit of cereal N nutrition. We conclude by considering the challenges of introducing in planta BNF into cereals and reflect on the potential for BNF in both conventional and alternative crop management systems to encourage the ecological intensification of cereal and legume production.
      原文链接:
    • NSTL
    • Elsevier

    Cover crops maintain or improve agronomic performances of maize monoculture during the transition period from conventional to no-tillage

    Alletto L.Cassigneul A.Duchalais A.Brechemier J....
    12页
    查看更多>>摘要：? 2022 Elsevier B.V.Maize monoculture systems often cause environmental impacts such as soil erosion, nitrate leaching and pesticide transfer. Conservation tillage and the use of cover crops appear to hold promise for limiting these impacts, but questions about their performance remain, particularly during the transition period after conventional soil tillage ceases. In this study, effects of no-tillage maize and fallow-period management with different cover crop species, either pure or in mixtures, were studied on the agronomic performance of maize and on soil N and water dynamics. The study combined field experiments over three years (2012–2014) and simulation modelling with the STICS model. The biomass of cover crops produced during the fallow period varied from 0.8 to 10.5 t dry matter ha?1 depending on the cover crop species and date of termination. Differences in soil water content were quantified among the treatments studied, with the lowest water content at the beginning of the maize growing season with late termination of a cover crop composed of pure faba bean or a vetch-oat mixture in 2014 (25–50% of plant-water available capacity). Maize grain yields ranged from 8.5 to 13.6 t dry matter ha?1, with the lowest yields in the bare soil treatment. Simulations with STICS were consistent with the observations and indicated a decrease in drainage of 8–38 mm year?1, depending on the year and cover crop. Introducing cover crops into maize systems is a powerful mechanism for maintaining production while improving environmental performances during the transition phase of soil properties in conservation tillage.
      原文链接:
    • NSTL
    • Elsevier

    Farm-scale practical strategies to increase nitrogen use efficiency and reduce nitrogen footprint in crop production across the North China Plain

    Yang Y.Zou J.Huang W.Hu S....
    13页
    查看更多>>摘要：? 2022 Elsevier B.V.Achieving a pathway for green development is a critically important challenge for agriculture in China and beyond. The current study evaluates the effects of a range of management interventions including planting, fertilizer nitrogen (N) rate optimization and increasing farm size to promote agricultural green development across the North China Plain (NCP) based on large-scale farm surveys. Our results showed that the mean annual N fertilizer rate for wheat-soybean rotation was much lower than that of wheat-maize and wheat-peanut. Interestingly, our study indicated strong pre-crop effects of summer soybean (Glycine max (Linn.) Merr.) on the following winter wheat (Triticum aestivum Linn.) in N saving compared to summer maize (Zea mays Linn.) and summer peanuts (Arachis hypogaea Linn.), the low N rate for summer soybean and its ‘legume’ carryover effects led to the low N rate, N surplus and N footprint, and high N use efficiency (NUE) in wheat-soybean. The survey results showed that the optimal N rates for achieving maximum yield of summer maize, summer peanuts and winter wheat were 229, 249 and 236–260 kg ha?1 across the NCP, respectively. Moreover, better N management is beneficial for reducing the N surplus and leads to higher NUE and lower N footprint. Generally, large farms applied less N fertilizer than small farms, thus leading to a lower N surplus and higher N partial factor productivity with the same yield level. Here we show for the first time that the combinations of crop rotation design, optimizing N rate application and increasing farm size are very efficient in reducing N fertilizer applications and the N footprint with stable crop yields. N management should play a more important role in agricultural green development across the NCP and similar regions around the world.
      原文链接:
    • NSTL
    • Elsevier

    Nitric oxide reduces the yield loss of waterlogged cotton by enhancing post-stress compensatory growth

    Zhang Y.Liu G.Xu S.Dai J....
    10页
    查看更多>>摘要：? 2022 Elsevier B.V.Waterlogging stress hampers cotton growth and development, ultimately causing yield loss. Nitric oxide (NO) was previously found to alleviate waterlogging damage to cotton plants, but it is unclear whether NO can enhance compensatory growth after waterlogging relief. Herein, field-grown cotton (Gossypium hirsutum L.) plants at peak flowering were subjected to a 10-day waterlogging stress treatment, and the effects of foliar spraying of sodium nitroprusside (SNP)—a NO donor—during waterlogging were evaluated. The NO concentrations in the plant tissues, plant biomass, and related physiological events at 10 d post-waterlogging relief, as well as the seedcotton yield and yield components at harvest, were measured over two consecutive years. Non-waterlogged and waterlogged cotton exhibited 38.5% and 48.3% increased plant biomass at 10 d post-waterlogging relief, respectively, compared with that on the day of stress relief, indicating that significant compensatory growth occurred following stress relief. Foliar spraying cotton with SNP during waterlogging not only increased the NO concentration (40–183%) before stress relief, but also increased the NO concentration (30–75%) after stress relief compared with no SNP application. As the NO concentration increased, plant biomass at 10 d post-waterlogging, as well as biological yield, boll density, and seedcotton yield of waterlogged cotton at harvest, were increased by 54.4%, 8.0%, 7.5%, and 7.6% under foliar SNP spraying compared to no SNP spraying, indicating that NO promoted compensatory growth and reduced the yield loss of waterlogged cotton. Correlation analysis showed that yield loss reduction was positively correlated with compensatory growth (R2 = 0.83**). Foliar spraying of SNP decreased the malondialdehyde content and the activities of alcohol dehydrogenase and pyruvate decarboxylase in waterlogged cotton at 10-d post stress relief by 15.2%, 42.4%, and 38.2%, but increased the contents of auxin (IAA), gibberellic acid (GA), and chlorophyll and the photosynthetic rate by 28.6%, 59.6%, 12.1%, and 6.4%, respectively, and decreased the abscisic acid (ABA) and ethylene contents by 12.5% and 8.5%, respectively, compared to no SNP spraying. In conclusion, foliar spraying of SNP increased the content of NO in waterlogged cotton plants even at 10-d post stress. Hormonal rebalance was realized through increased IAA and GA and reduced ABA and ethylene due to the elevated NO content, which promoted photosynthetic recovery and compensatory growth after stress relief, ultimately reducing yield loss. The overall results indicated that enhancing the compensatory growth of cotton after waterlogging is an important mechanism by which NO mitigates waterlogging stress.
      原文链接:
    • NSTL
    • Elsevier

    Soil warming and straw return impacts on winter wheat phenology, photosynthesis, root growth, and grain yield in the North China Plain

    Wu G.Ling J.Liu Z.-X.Xu Y.-P....
    10页
    查看更多>>摘要：? 2022 Elsevier B.V.Soil temperature rise caused by global warming is one of the most serious threats to crop physiology and production. Straw return is considered as a potential strategy to improve soil health and agricultural productivity. However, little is known about their interactive effects on wheat growth and production, which limits the development of strategies and technological innovations for future food security. Therefore, in the two wheat seasons from 2018 to 2020, with or without straw return, the heating cable was laid at a depth of 20 cm to increase the soil temperature by 3.8 ℃, and the phenology, photosynthesis, root growth, and grain yield of winter wheat were studied. Soil warming advanced the anthesis date by one week and promoted pre-anthesis wheat growth and dry matter transportation. However, soil warming decreased post-anthesis duration, leaf area index, SPAD, net photosynthesis, and spectral vegetation indexes. Therefore, post-anthesis dry matter accumulation and grain filling were inhibited, lowering the 1000-grain weight and harvest index. Furthermore, the post-anthesis root weight, length, surface area densities and root to shoot ratio were also decreased under soil warming. Finally, soil warming reduced the grain yield by 35.2% in the dry 2018–2019 year. However, the wheat growth characteristics were considerably higher and no difference in grain yield was detected among treatments in the wet 2019–2020 season, indicating that increased precipitation may offset the adverse effect of soil warming on wheat yield. Straw return increased aboveground biomass, but had no effect on wheat yield, probably because the positive effects were limited in the short experimental duration. The findings suggested that soil warming would promote pre-anthesis wheat growth but accelerate post-anthesis wheat senescence, affect dry matter transportation and accumulation, eventually reducing wheat yield in the NCP, especially under dry condition.
      原文链接:
    • NSTL
    • Elsevier

    Chemical topping improves the efficiency of spraying harvest aids using unmanned aerial vehicles in high-density cotton

    Tian X.Li Z.Liu Y.Zhang Z....
    9页
    查看更多>>摘要：? 2022 Elsevier B.V.The cotton defoliation strategy is highly appreciated in Xinjiang, where mechanical harvesting is limited by a large proportion of green leaves and unopened bolls at harvest due to an insufficient temperature sum. Because of a high plant density, the application of defoliants (harvest aids) by tractors is less efficient; thus, unmanned aerial vehicles (UAVs) for spraying harvest aids are becoming more and more popular. However, it is unknown if this method affects spraying quality and whether the spray is affected by the cotton plant type that was shaped by chemical topping. This study aims to address if chemical topping could enhance defoliation when harvest aids is sprayed using UAV. Field experiments were carried out in 2019 and 2020 in Alaer, Xinjiang, China. The topping treatments included manual topping (MT) as the control and chemical topping (CT) that inhibit apical growth of the stem by foliar application of mepiquat chloride (MC) at 90 (MC90), 180 (MC180), or 270 (MC270) g ha–1 in mid-July. The harvest aids was sprayed in mid-September using UAVs. The average droplet deposition and deposits of harvest aids within the canopy in CT and MT were not different in 2019. However, the average droplet deposition and deposits of CT were much higher than those of MT in 2020. Both droplet deposition and deposits decreased with canopy height, and the droplet distribution performance of CT was better than that of MT. The droplet deposition and deposits in the upper and middle canopy of CT were significantly higher than those of MT in 2020. At 21 days after harvest aids application, the number of leaves per plant in CT was significantly lower than that in MT, while there was no difference between the amounts of MC. CT did not affect boll opening. Moreover, the yield and quality were not affected by harvest aids application using UAVs and CT. We concluded that spraying harvest aids using UAVs combined with CT improved management efficiency and economic benefits by saving labor, without loss of cotton yield and quality. Our results demonstrate that applying harvest aids using UAVs in cotton with CT could improve the quality of defoliation and provide a reference for optimizing cotton managements globally.
      原文链接:
    • NSTL
    • Elsevier