Crop growth stages are integral components of plant phenology and are of significant ecological and agricultural importance. While the use of remote sensing methods for phenology identification in cropland ecosystems has been extensively explored in previous studies, the focus has often been on land surface phenology, primarily related to the start and end of the growing season. In contrast, the monitoring of crop growth within an agronomic framework has been limited, particularly in the context of recently developed solar-induced chlorophyll fluorescence (SIF) data. Additionally, some critical growth stages have not received adequate attention or evaluation. This study aims to assess the utility of SIF data, collected from both ground and satellite measurements, for identifying critical crop growth stages within the realm of remote sensing phenological estimation. A comparative analysis was conducted using enhanced vegetation index (EVI) data at the Shangqiu site in the North China Plain from 2018 to 2022. Both SIF and EVI time-series data, obtained from ground and satellite sources, undergo a comprehensive phenological estimation framework encompassing pre-processing, modeling, and transition characterization. This approach involves reconciling time-series phenological patterns with crop growth stages, revealing the necessity of redefining the mapping relationship between these two fundamental concepts. After preprocessing the time-series data, the framework incorporates the phenological modeling process employing two double logistic models and a spline model for comparison. Additionally, it includes phenological transition characterization using four different methods. Consequently, each input dataset undergoes an assessment, resulting in 12 sets of estimations, which are compared to select the ideal estimation portfolio for identifying the growth stages of maize and winter wheat. Our findings highlight the efficacy of SIF data in accurately identifying the growth stages of maize and winter wheat, achieving remarkable results with an R-square exceeding 0.9 and an RMSE of less than 1 week for key growth stages (KGSs). Notably, SIF data demonstrate superior accuracy, robustness, and sensitivity to phenological events when compared to EVI data. This study establishes an estimation portfolio utilizing SIF data, involving the Gu model, a double logistic model, as the preferred phenological modelling method together with various compositing methods and transition characterization methods, suitable for most KGSs. These findings create opportunities for future research aimed at enhancing and standardizing crop growth stage identification using remote sensing data for a wide range of KGSs.

Our research is aimed at exploring quality differences in different water sources， and the influence on quality of precipitation， shallow groundwater depth， and other factors in an agricultural ecosystem. Samples of flowing surface water and shallow groundwater were collected from 4 locations near the National Agro-ecological System Observation and Research Station of Shangqiu in Henan province to monitor water quality from 2011 to 2020. Quality of these two water sources was studied as a dynamic process to identify influencing factors using descriptive statistics and a time series analysis method. Ca 2+ ， Mg 2+ ， Na + ， HCO 3 - ， SO 4 2- and Cl - content and electrical conductivity were usually higher in poorly renewed shallow groundwater than in flowing surface water. Rises in the underground water table caused by increased precipitation could promote salt ion migration from top soil to groundwater， thereby amplifying discrepancies between these two kinds of water. spanning 10 years of monitoring， peak values were observed for all ions， during which Na + ， Ca 2+ and SO 4 2- in flowing surface water and K + in shallow groundwater reached their maxima in March 2012 and September 2011 respectively. The hydrochemical types of these two waters were consistently similar over time. Although seasonal variation exerted less influence on periodical ion content changes， the long-term dynamic interaction between precipitation and the groundwater table notably regulated the hydrochemical type and ion flux in the waters. In the scenario in which increased precipitation raised the water table， shallow groundwater SO 4 2- ， and Cl - levels could easily exceed the threshold for agricultural production suggested by groundwater quality criterion （GB/T 14848—2017）， rendering it unsuitable for irrigation. This study confirmed that long-term quality in flowing surface water and shallow groundwater was dynamically influenced by long-term changes in precipitation and groundwater depth in a typical agricultural ecosystem in eastern Henan， which can provide a reference for water quality risk management in farmland environments and water source selection in local agriculture production.

【Objective】 Rotating winter wheat and summer maize is a common cultivation method in northern and central China. Their water consumption and the occurrence of water deficit vary with prediction. Taking Shangqiu in easter Henan province as an example, this paper investigates the relationship between them with meteorological factors. 【Method】 The analysis was based on meteorological data measured from 1954 to 2019, and crop index data measured from 1999 to 2019 at the National Agro-ecological System Observation and Research Station of Shangqiu. The evapotranspiration used in the analysis was those measured from 2011 to 2018 from a large lysimeter. Statistics and the Mann-Kendall trend test were used to analyze the changing in crop water requirement and water deficit; the dominant analysis was used to elucidate the influence of the meteorological factors on water requirement of the two crops. 【Result】 On average, the annual effective precipitation has been increasing over the past 65 years, at a rate of 3.09 mm/10a during the wheat growing season and 5.23 mm/10a during the maize growing season, despite that in wet years the effective precipitation during the wheat season declined. In contrast, the annual crop water requirement showed a decline (P<0.01), at a rate of 6.72 mm/10a for the winter wheat and 18.47 mm/10a for the maize, regardless of precipitations. The annual crop water deficit had also shown a falling trend (P<0.01), at a rate of 9.81 mm/10a for the winter wheat and 23.70 mm/10a for the maize, despite that it decreased for the winter wheat in wet years. In normal and dry years, sunshine was the primary meteorological factor affecting water requirement of the winter wheat, whine in wet years, humidity was the primary factor. The primary factors affecting water requirement of summer maize were sunshine, regardless of precipitation, despite that wind speed and high temperature also played a role. 【Conclusion】 Our analysis revealed that in wet years, winter wheat should be irrigated during jointing - heading stage, while maize can grow under rain-fed condition. In normal years, winter wheat needs irrigation at jointing - heading stage and maize needs irrigation at tasseling stage. In dry years, in addition to an irrigation before seeding, winter wheat needs irrigation at joint-heading stage and summer maize at joint-tasseling stage.

Tropospheric ozone (O 3 ) is phytotoxic air pollutant for crops with oxidant nature. Maize ( Zea mays L. ) is a staple crop that is grown worldwide and its sensitivity to the air pollution O 3 depends on the cultivar. However, few studies investigated the intraspecific variations in O 3 sensitivity of maize. The present study assessed the response of five maize cultivars to ambient O 3 in relation to gas exchange, photosynthetic pigments, biomass allocation and yields using ethylenediurea (EDU), which was given as a foliar spray (400 ppm) at an interval of 10 days after germination up to maturity in North China Plain. During the maize growing season, the 12-h O 3 concentration ranged from 21.3 to 91.3 ppb (average 55.5 ± 14.7 ppb) with the accumulated O 3 exposure above an hourly threshold of 40 ppb (AOT40) of 24.4 ppm h. In comparison with EDU-treated maize, maize with no protection from ambient O 3 significantly reduced yield by 8.4% for YH988 and 8.1% for XD20, but not significantly for other three cultivars (0.5% to 5.0%). We also found ambient O 3 did not significantly decrease maize total biomass as well as root biomass. Our results provide the evidences that ambient O 3 mainly causes maize yield losses by decreasing gas exchange rather than damaging photosynthetic pigments. The large intraspecific changes in O 3 sensitivity among the maize cultivars should be considered in estimating O 3 -caused maize yield losses especially in the hotspots of ambient O 3 pollution regions.

Available information on the microbial mechanisms associated with heavy metal (HM) passivation during co-composting amended with phosphate rock (PR) remains limited. Thus, this study investigated the dynamic changes in bacterial communities and HM-fractions (Zn, Cu, Cd, Cr and Pb) during swine manure composting with maize straw, and ascertained the bacterial influence on HM-passivation. The results demonstrated that the addition of PR improved HM-passivation, especially for Zn and Cd, with their bioavailability factors (BFs) reduced by 247.41 and 176.25%, respectively. As for bacterial communities, the proportion of Firmicutes decreased, while the proportions of Proteobacteria, Bacteroidetes, Deinococcus-Thermus and Gemmatimonadetes increased in all treatments. PR significantly changed the primary bacterial phyla in the thermophilic phase. Bacteroidetes were the main bacterial component controlling the passivation of Zn, Cu and Cr, while Deinococcus-Thermus mainly regulated the mobility of Zn and Pb, and Proteobacteria only dominated the transformation among Cd-fractions. These results may provide a reference for the use of HM-passivation techniques during composting.

Available information on passivation effect of biochar on heavy metals (HMs) through regulating bacterial communities remains limited. Thus, this study investigated the correlation between bacterial diversity and HM-fractions (Zn, Cu, Cd, Cr and Pb) during composting with different dose of biochar (5% and 10%, dry weight basis), in order to ascertain the passivation effect on HMs under the influence of bacterial community. The addition of 10% biochar showed better passivation effect with reduction in bioavailability factor (BF) of Zn, Cu, Cd and Pb by 4.10%, 44.12%, 18.75% and 30.06%, respectively. In addition, it brought forward the variation in primary bacterial phylum to the thermophilic phase. The results of redundancy analysis (RDA) and structural equation models (SEMs) indicated that C:N ratio was an important factor in controlling the morphological transformation of HM by affecting the bacterial community structure. Our results maybe provide a novel insight into HM-passivation from an interaction mechanism on C:N ratio and bacterial community.

Given that Cd pollution in dry land has aroused wide public concern, numerous remediation technologies has been utilized, yet there are limited cost-effective techniques that do not affect the original planting patterns. Fortunately, irrigationmanagement can meet these requirements, while the effects of irrigation practices on Cd uptake by crops in slightly Cd-polluted upland soil remain elusive. Here, we aimed to investigate howthe irrigation methods altered the Cd availability in soil, Cd accumulation in plants, microorganism population in soil, rootmorphology, and enzyme activities in soil and plants. We examined three irrigation treatments - surface drip irrigation (DI), subsurface drip irrigation (SDI), alternate-rows irrigation (ARI), and the control conventional furrow irrigation (CFI). The results showed that SDI remarkably reduced Cd content in roots, shoots and fruits, increased yield, and improved root growth and activity in soil of 20-40 cm compared to other treatments, though the Cd concentration in rhizosphere was not decreased significantly. The microbial population and enzyme activities in rhizosphere and enzyme activities in leaves and roots in SDI and ARI were basically higher than DI and CFI. Therefore, SDI has the prominent potential to reduce Cd uptake by crops in upland soil polluted with low Cd. (C) 2020 Elsevier B.V. All rights reserved.

Solar-induced chlorophyll fluorescence (SIF) has shown to be a good proxy of gross primary production (GPP) across multiple spatial and temporal scales. The dependence of top-of-canopy measurements of SIF on the illumination and observation directions has been recognized as an important factor in the relationship between SIF and GPP across multiple spatiotemporal scales. In this study, we investigated angular effects in diurnal observed SIF (SIFobs) measurements taken with a multi-angle SIF measuring system in a wheat-corn rotational field during the growing season of 2018. Our results reveal strong angular dependencies in diurnal measurements of top-of-canopy SIF for both red SIF obs (RSIFobs) and far-red SIFobs (FRSIFobs). We also observe that the correlation between SIF obs (RSIF obs and FRSIFobs) and GPP depends on both the illumination and viewing directions. To mitigate angular effects in SIFobs, an approach based on spectral reflectance measurements was used. The derived canopy total SIF emission (SIFtotal) at both red and far-red bands (RSIFtotal and FRSIFtotal) showed less angular dependencies and stronger relationships to APAR and GPP than RSIFobs and FRSIFobs. These results highlight the important role of angular effects in SIF when interpreting directional SIF obs retrievals from space, which normally include large variations in sun-target-viewing geometries. This study contributes to our understanding of angular effects on SIF-GPP relationships and subsequently help improve the estimation of GPP from SIF data.