Field Water Balance Research Articles

Hydrologic variability governs GHG emissions in rice-based cropping systems of Eastern India

Reducing methane (CH4) emissions is increasingly recognized as an urgent greenhouse gas mitigation priority for avoiding ecosystem ‘tipping points’ that will accelerate global warming. Agricultural systems, namely ruminant livestock and rice cultivation are dominant sources of CH4 emissions. Efforts to reduce methane from rice typically focus on water management strategies that implicitly assume that irrigated rice systems are consistently flooded and that farmers exert a high level of control over the field water balance. In India most rice is cultivated during the monsoon season and hydrologic variability is common, particularly in the Eastern Gangetic Plains (EGP) where high but variable rainfall, shallow groundwater, and subtle differences in topography interact to create complex mosaics of field water conditions. Here, we characterize the hydrologic variability of monsoon season rice fields (n = 207) in the Indian EGP (‘Eastern India’) across two contrasting climate years (2021, 2022) and use the Denitrification Decomposition (DNDC) model to estimate GHG emissions for the observed hydrologic conditions. Five distinct clusters of field hydrology patterns were evident in each year, but cluster characteristics were not stable across years. In 2021, average GHG emissions (8.14 mt CO2-eq ha−1) were twice as high as in 2022 (3.81 mt CO2-eq ha−1). Importantly, intra-annual variability between fields was also high, underlining the need to characterize representative emission distributions across the landscape and across seasons to appropriately target GHG mitigation strategies and generate accurate baseline values. Simulation results were also analyzed to identify main drivers of emissions, with readily identified factors such as flooding period and hydrologic interactions with crop residues and nitrogen management practices emerging as important. These insights provide a foundation for understanding landscape variability in GHG emissions from rice in Eastern India and suggest priorities for mitigation that honor the hydrologic complexity of the region.

Field and simulation studies on yield, water and nitrogen dynamics and use efficiency in rice-wheat crops in sequence

ContextThe dominant rice-wheat cropping system in the Indo-Gangetic plain faces challenges of water depletion and nitrogen pollution of groundwater as well as declining productivity caused by over irrigation and nitrogen fertilization by the farmers. To appreciate the apt use of irrigation water and nitrogen fertilizer in rice and wheat crops it is essential to explore the water and nitrogen balances as well as dynamics in these crops, involving complex interaction between weather, soil, irrigation water and nitrogen fertilizer management. ObjectiveThe objective of the study is to quantify yield, field water balance components, water use efficiency, water productivity, water footprint, and water and nitrogen dynamics of rice and wheat crops in relation to season, varieties, irrigation regimes and nitrogen levels. MethodsField experimentations were conducted in double split plot design along with calibrated and validated HYDRUS 1D model use for two years comprising of treatments in rice i.e. two varieties (PR122-V1 and PR126-V2), two irrigation regimes (2-days drainage period-I1 and soil water suction 16 kPa-I2) and two nitrogen levels (120-N1 and 90-N2 kg N ha−1); and in wheat, two varieties (Unnat PBW343-V1 and Unnat PBW550-V2), two irrigation (1.2 IW/CPE-I1 and 0.9 IW/CPE-I2) regimes and two nitrogen levels (120-N1 and 90-N2 kg N ha−1). ResultsThe highest grain yield recorded was 7.6 t ha−1 in treatment combination of V1I2N1 in rice and 5.4 t ha−1 in V1I1N1 in wheat owing to better plant growth and yield attributes (biomass production, number of effective tillers, panicle length, and 1000 grain weight). Total water footprints were lower in the treatment combination of V1I1N1 in rice and V1I2N1 in wheat. The water budget revealed a higher percent contribution of the total water input to drainage (62 %) in rice ensuing restoration of water in the soil profile; and to evapotranspiration (ET) (100 %) in wheat ensuing water depletion. Modeling water and nitrogen dynamics showed higher root water uptake in I2 treatment in rice and with I1 treatment in wheat; and leaching losses of NO3-N under rice than wheat; and under I2 treatment than I1 as well as in N1 than N2. ConclusionsThe V1I2N1 treatment in rice and V1I1N1 treatment in wheat demonstrated superior grain yield, soil water storage, and root water uptake. Conversely, V1I1N1 treatment in rice and V1I2N1 treatment in wheat showed higher water use efficiency and lower water footprint. SignificanceIt helps to evaluate the effectiveness of irrigation and nitrogen management strategies in maximizing crop productivity while minimizing environmental impacts.

Hydrological effects of open ditch damming and controlled subsurface drainage in a Nordic agricultural field

Abstract Controlled drainage (CRD) is an agricultural water management practice designed to adjust the capacity of a drainage system under varying hydrological conditions. This simulation study aimed to quantify the potential of combining a controlled subsurface drainage (CS) with open ditch damming (CD) to manage the water table depth (WTD) and field water balance in Nordic conditions. Simulations with and without controlled drainage were run using a hydrological model that had been set up for a flat loamy field in Northern Ostrobothnia, Finland, for the period 2010–2021. All CRD scenarios reduced the probability of deep WTDs during growing seasons (May–Sep). The impact of CS on WTDs was greater and more uniform than CD. The CRD effects on water balance were seen in water outflow pathways, as CS reduced drain discharge while CD had the opposite effect. When both methods were applied simultaneously, annual evapotranspiration increased 5–12% compared with the free drainage scenario. The effects of CRD on evapotranspiration were greatest during the dry years indicating that CRD has potential to reduce drought in food production areas. None of the CRD scenarios could maintain optimal WTDs during the entire growing season, highlighting the complexity of optimizing field water management using CRD alone.

Estimation of crop evapotranspiration and crop coefficient for coriander using Portable Automatic Closed Canopy Chamber

An experiment was carried out to determine crop evapotranspiration and crop coefficient of Coriander crop by using Portable Automatic Closed Canopy Chamber (PACCC), Micro-Lysimeter (MLs) and field water balance (FWB) methods. The results revealed that there was no significant difference in the coriander crop evapotranspiration measured by the MLs inside and outside the PACCC and no significant difference among the crop evapotranspiration measured by the PACCC, MLs and FWB at 95 percent confidence level was found. It is indicating that, there are no effects of the change in micro-climate for a short period of 2 minutes in the chamber and on the plant physiological processes. During validation of PACCC, the average crop coefficients measured by MLs were varied from 0.66 to 1.26 for coriander crop. However, the stage wise crop coefficients of corianders measured by FWB were varied from 0.67 to 1.28 during field testing of PACCC. The result showed that the PACCC can be used for measurement of crop evapotranspiration in the field condition.

In-field assessment of the variability in water and nutrient use efficiency among potato farmers in a semi-arid climate

Precise water management is imperative for sustainable crop production under irrigation in semi-arid regions with increasingly variable rainfall. Water use efficiencies achieved by farmers often differ widely, even within regions with homogenous agro-ecological conditions. To better understand the drivers of this variability and derive management recommendations, detailed measurements of water and associated nutrient dynamics were conducted on 20 potato farms in two regions of South Africa. Crop characteristics and typical growing conditions in South Africa make potato cultivation sensitive to water and nutrient losses. Water and nutrient inputs and losses through drainage and plant uptake were measured in potato and the follow-up crop, along with yield and weather variables. Seasonal mean irrigation and evapotranspiration were lower in winter crops (240 mm irrigation, 236 mm evapotranspiration) than in summer crops (598 mm irrigation, 608 mm evapotranspiration). Seasonal field water balances were often close to zero, indicating that estimations of evapotranspiration and drainage were representative for the greater field. Lysimeter observations however appeared more representative in sandy unstructured soils than in heavier structured soils. Rainfall during cropping reduced demand for irrigation and increased water use efficiency based on irrigation water, but caused substantial drainage. Leaching of N and K was considerable (on average 30 kg N, 55 kg K ha−1, much higher in some fields), while P leaching was negligible, with the exception of one field (51 kg P ha−1). Variation in water and nutrients use efficiencies was the result of management decisions and environmental factors, such as rainfall and soil type. Without substantial rainfall, application of irrigation scheduling tools can keep drainage and nutrient losses to a minimum, as was observed on almost half the fields, even on sandy soils with a low water holding capacity. Potato yields greatly varied among farmers (9.1–24.7 t dry matter tuber ha−1). Efficient farmers included those who used water sparsely and had minimal drainage, but also farmers who used inputs judiciously and obtained excellent productivity. The role of follow-up crops as users of surplus nutrients and water left behind by the potato crop was not always evident.

Setting Irrigation Thresholds for Building a Platform Aimed at the Improved Management of Citrus Orchards in Coastal Syria

Citrus is one of the most valuable crops in Syria, with the largest production areas being in the coastal provinces of Tartus and Latakia, where this study was performed. A companion paper reported on the basal crop coefficients derived from the field water balance and on the performance assessment of various irrigation methods used in a citrus orchard located in the same region. That study evidenced the need for the improved management of irrigation water, mainly reducing water applications and increasing productivity, thus leading to the current research. The main objectives consisted of (i) providing a set of reliable basal (Kcb) and average (Kc) crop coefficients to be used in practice in the citrus orchards of the Syrian coastal area, while accounting for the diversity of characteristics observed; (ii) to estimate the seasonal consumptive use of typical orchards under different climate-demand and deficit-irrigation scenarios; and (iii) to assess possible water savings and related yield reductions. The previously calibrated water balance model SIMDualKc was used for these purposes. The computed Kcb values for the mid-season and average demand for water ranged from 0.52, when the plant density was low, to 0.84, when plant density was very high. The corresponding Kc values, which further reflected the impact of drip irrigation on controlling soil evaporation, were 0.72 and 0.97, respectively. Overall, the consumptive use of water was estimated to range from 867 to 1573 mm. The assessed water-saving scenarios consisted of adopting increased management-allowed depletion (MAD) thresholds relative to the p depletion fraction for no stress: MAD = 1.05, 1.10, 1.20, and 1.30 p. For trees under a very high climatic demand, water savings ranged from 12 to 34%, but the yield losses induced by the water deficits ranged from 8 to 48%. Although the selection of optimal strategies should be based upon economic terms, these may only be used when the Syrian economy recovers from civil war and the current crisis. The present results show the feasibility of adopting such MAD thresholds for building an irrigation management platform. The data provided by the current study are valuable because they can be efficiently used to support of the irrigation management of Syrian citrus production systems.

Prediction of Rubber Yield Based on Soil Water Content

Fluctuation of monthly rainfall resulted in fluctuation of monthly rubber yield. This study was aimed to determine a model to predict rubber yield based on soil water content. This study was conducted at Indonesian Rubber Research Institute, South Sumatera in May 2022. The plant materials used in this study were rubber clones PB 260 that were planted in 2001 in two blocks of rubber field. The soil texture in these two blocks was clay loam with good drainage conditions. The average of monthly soil water content and rubber yield data for 11 years from the first block was used to determine the model. Whereas the average of monthly soil water content and rubber yield data for 12 years from the second block was used to validate the model. The soil water content was generated by field water balance calculation. The regression and correlation analysis showed that the highest correlation and the most suitable model to predict rubber yield based on soil water content was the power model with formula Y = 0.0668X2.1423 (coefficient of determination (R2) = 0.80). Where, Y = rubber yield (kg/month) and X = soil water content (%). Furthermore, the validation of the model showed that the goodness of match (GOM), Pearson correlation coefficient (R), coefficient of determination (R2), and root mean square error (RMSE) were 0.94, 0.95, 0.90. and 10.3 respectively. These values showed that the model was accurate and strong enough to predict rubber yield based on soil water content.

A VBA-Based Field Water Balance Model for Efficient Irrigation Water Management of Corn (Zea mays L.)

A field water balance model for efficient irrigation water management of corn was developed using Excel VBA. The model consists of five sub-components or modules, namely, (1) a plant subcomponent, (2) an effective rainfall subcomponent, (3) an evapotranspiration subcomponent, (4) a soil water dynamics subcomponent for the modeling of water flow into and within the soil layers, and (5) an irrigation subcomponent for the estimation of the required amount and timing of irrigation. The model was calibrated and validated using observed data from field experiments and the results showed a reasonably good agreement between the observed and simulated soil moisture values (MAE = 5.76 mm to 12.00 mm, RMSE = 6.83 mm to 13.12 mm, NRMSE = 0.102 to 0.196, and NSE = 0.37 to 0.90). The simulations emphasized that a significant amount of water savings can be achieved when rainfall is properly accounted for in managing water in the field, and that the frequency of rainfall occurrences is as important as the magnitude of rainfall received by the crops. The wide-ranging user-friendliness and simplicity of the model developed in this study can pave the way to eliminating the barriers which cause farmers to resist advancements in their farming practices as the model can easily be used not only by researchers and scientists but also by farmers, especially those with basic knowledge of spreadsheets.

DRIP-IRRIGATED SWEET CORN WATER USE DEPENDING ON THE DEPTH OF PLOWING, MINERAL FERTILIZATION RATES AND CROPS DENSITY

The effect of plowing depth (20-22; 28-30 cm), mineral fertilization rates (N-P: 0-0, 60-60, 120-120 kg ha-1), and crops density (35,000, 50,000, 65,000, 80,000 plants ha-1) on the yield, and water use efficiency (WUE) of drip-irrigated sweet corn were studied. The field experiment was conducted in the semi-arid climatic conditions of the South of Ukraine (Kherson oblast) at the dark-chestnut middle-loamy soil. The trials were conducted using split-plot design in four replications. Irrigation scheduling and rates were set by the field water balance method considering the amounts of available soil moisture and precipitation. Manual harvesting of the crop ears was conducted at R3 phenological stage. WUE was calculated as the ratio of the ears’ yield to the gross water use of the crop. Statistical evaluation was performed by analysis of variance (ANOVA) and regression analysis at the probability level of 95%. The studied factors and their interaction had a significant effect on sweet corn productivity and WUE. The best crop productivity along with the best WUE was provided by plowing on 20-22 cm, fertilization rates of 120-120 kg ha<sup<-1</sup<, and crops density of 65,000 plants ha<sup<-1</sup<.

A review of crop water productivity in the Mediterranean basin under a changing climate: Wheat and barley as test cases

AbstractThe ever‐increasing water demands in the agricultural sector of the Mediterranean basin region (MBR) under climate change warrants that crop water productivity (WP) is a pertinent topic for discussion. Considering this need, this study aims to synthesize the body of knowledge on WP focusing on the MBR. The study is based on two test cases: (1) wheat, because it is a basic staple food in high dietary demand in the region and (2) barley, because it is a climate‐resilient alternative that is extensively cultivated in severe water‐ and salinity‐stress conditions. These staple crops are strategically important for regional food security in the MBR, which covers southern Europe, North Africa and western Asia. The study tries to investigate the plausible reasons for yield and WP gaps in the region. Our meta‐analysis revealed that wheat and barley are very different in their spatial distributions, productions and stress resiliencies in the MBR. Under the large gamut of biophysical and socio‐economic constraints that affect crop production, it is observed that the northern and southern parts of the MBR have large capacity differences (institutional, infrastructural and technical) in cereal production. It is noted that the role of soil‐water management in improving WP is vital and plays a critical role in closing yield gaps across the MBR. Moreover, the scaling of stress‐tolerant varieties along with a package of agronomic practices can enhance WP, and thereby we can make the region adaptive to climate change, especially in terms of water stress. The literature revealed that the MBR, especially the southern parts encompassing North Africa and western Asia, critically lacks comprehensive experimental/observational evidence on the dynamics of field water balance. This knowledge is key to enhancing WP assessments using modelling approaches. The paper concludes that the MBR does have water‐saving potential; it simply needs planned adaptation measures to enhance WP at the local and regional scales with effective benchmark studies in future.

Plastic film mulching affects field water balance components, grain yield, and water productivity of rainfed maize in the Loess Plateau, China: A synthetic analysis of multi-site observations

Plastic film mulching (PM) has been widely practiced for rainfed maize (Zea mays L.) in the Loess Plateau, China. However, controversy remains regarding its impacts on field water balance components. There is also scant quantitative information on water-limited potential grain yield (GYw) and water productivity (WPw). A meta-analysis and boundary line analysis were conducted using 1421 paired observations extracted from 83 peer-reviewed publications to (1) assess PM-induced changes in soil water storage at planting (SWSP), evapotranspiration (ET), and soil water storage at harvest (SWSH), and (2) quantify GYw and WPw in PM fields. PM significantly increased SWSP by 4.0% on average due to an 83.2% average increase in precipitation storage during the fallow season. Overall, ET showed a significant positive response to PM (+2.9%), resulting in 56.4% more soil water depletion than no-mulching (NM) fields over the growing season. However, SWSH significantly increased by an average 1.8% after applying PM, indicating that increased storage of fallow season precipitation replenished increased depletion of growing season soil water. Averaged across all samples, PM had significant positive effects on GY (+56.1%) and WP (+47.5%), which were attributed to higher transpiration, ratio of transpiration to ET, and harvest index from the perspective of effective crop water use. Based on GY and WP boundary lines, GYw and WPw under NM were estimated to be 10,728 kg ha-1 and 26.8 kg ha-1 mm-1 on average, respectively, and the respective averages under PM were 13,702 kg ha-1 and 34.8 kg ha-1 mm-1. The GY and WP gaps (i.e., differences between actual and potential values) averaged around 3300 kg ha-1 and 7.0 kg ha-1 mm-1, respectively, in NM and PM fields. In the GY versus ET and WP versus ET scatter plots, the vertical distances between the measured data points on a specific field and the corresponding boundary line indicated field-specific gaps for GY and WP. This study increases our understanding of the effect sizes of PM on field water balance components and the benchmarks of GY and WP for rainfed maize in the Chinese Loess Plateau and other regions with similar conditions worldwide.

Assessing soil water balance to optimize irrigation schedules of flood-irrigated maize fields with different cultivation histories in the arid region

Water availability is the most critical restriction for sustainable crop plantation in the arid region; consequently, it is essential to quantify the soil water balance and optimize the irrigation schedules in the farmland. However, the effects of cultivation history on crop field water balance and optimized irrigation design were rarely studied. In this study, three typical maize (Zea mays L.) fields with different cultivation histories (i.e., old oasis maize field, OF; new maize field developed from a wetland, NFW; new maize field developed from the desert, NFD) in arid regions of Northwest China were selected, which had major differences in soil textures and GWLs. Based on one growth season (i.e., from April 30th to September 30th) in situ field monitoring (e.g., soil water content, maize growth index, meteorological data) and numerical model (HYDRUS-1D) simulation, the water balance and root water uptake deficit in these fields were quantified, and optimized irrigation schedules were proposed. During the maize growth period under the current irrigation schedule, the highest percolation was observed in OF (364 mm), followed by NFD (231 mm) and NFW (−52 mm). The soil water in NFW was obviously recharged by the capillary rise from groundwater, while the OF and NFD were not. Also, the most severe water deficit was identified in NFD, followed by NFW and OF. Compared with the current irrigation schedule, the irrigation was reduced by 65%, 45%, and 13% under the optimized irrigation amount in NFW, OF, and NFD, respectively. Furthermore, it was reduced by 84%, 61%, and 23% under both irrigation time and amount optimized in NFW, OF, and NFD, respectively. Under either optimized irrigation, the water deficit was relieved, deep percolation was reduced during the maize growth period, and less soil water was stored after maize was harvested. Especially under irrigation time and amount optimizing, the least irrigation times (4) and amount (90 mm) were applied in NFW among three fields, ascribing to a large amount of water recharge from shallow groundwater by capillary rise. Due to the soil texture differences, fewer irrigation times (6) with considerable single irrigation amount (30–70 mm) was recommended for OF with loamy soil, whereas more irrigation times (12) with less single irrigation (25–50 mm) were appropriated for NFD with sandy soil. It concluded that the effects of soil texture and GWL should be well considered for optimizing irrigation schedules.

Controlled drainage under two climate change scenarios in a flat high-latitude field

Abstract This simulation study focused on the hydrological effects of climate change and controlled drainage operated with subsurface drains and an open collector ditch in an agricultural field. The objective was to understand the potential of controlled drainage and open ditch schemes for managing groundwater levels and field water balance in climate conditions projected to take place in Finland during the 21st century with representative concentration pathways 8.5 and 2.6. A methodological aim was to find ways to condense hourly hydrological results to understand future changes in field hydrology. During the historical reference interval (1970–2005), controlled drainage caused 17–36 cm higher mean groundwater levels and decreased the mean annual drain discharge by 11–23% compared to conventional subsurface drainage. Controlled drainage was projected to increase groundwater levels by additional 1–4 cm in the future compared to its effect on drainage during the reference interval. The effect on annual drain discharge did not change significantly. The open collector ditch lowered groundwater tables and diminished the effect of controlled drainage on groundwater levels in the vicinity of the ditch. Controlled drainage was shown to remain an effective method for countering early summer drought and reducing drain discharge.

Seasonal effects of controlled drainage on field water balance and groundwater levels

Abstract Adaptive water management solutions such as controlled drainage have raised interest in Nordic areas due to climate variability. It is not fully known how controlled drainage affects seasonal field water balance or can help in preventing water scarcity during dry growing seasons (GSs). The objective was to simulate the effects of controlled drainage on field hydrology using a well-tested, process-based hydrological model. The FLUSH model was calibrated and validated to an experimental field. The model performance with non-local input data was moderate but acceptable for running the controlled drainage scenarios to test the response of the water management method to meteorological forcing. Simulation results showed that controlled drainage reduced drain discharge while increasing surface layer runoff and shallow groundwater outflow. Groundwater depths from the scenario simulations demonstrated that controlled drainage could keep the depth closer to the soil surface, but the effect diminished during the dry conditions. Controlled drainage can be used to change the water flow pathways but has a secondary effect compared with the primary meteorological drivers. The field data set and FLUSH formed a novel computational platform to study the impacts of different water management options on the whole water balance and spatial variability of groundwater depths.

Analysis of crop water requirements and irrigation demands for rice: Implications for increasing effective rainfall

Determining the irrigation demands of rice in a humid region is essential for water conservation through improving rainfall utilization in southern China. In this paper, six representative rice areas in southern China were selected, and the daily reference evapotranspiration (ETo) of the representative stations during 1953–2017 was calculated using the Penman-Monteith method. The daily crop evapotranspiration (ETc) was computed using the single crop coefficient method, and the irrigation scheduling under flood irrigation (FI) was obtained by establishing a field water balance model. The characteristics and trends of the irrigation demand of early, middle and late rice, as well as the irrigation changes under a “double-to-single” cropping pattern, were also analyzed with advanced statistical tests. The results indicated that most of the abundant rainfall was concentrated in the growth period of early rice in southern China. Early rice required less water (135.0 mm) and even no irrigation in some wet years, while middle and late rice required more irrigation water (288.1 mm and 265.2 mm, respectively). The key reasons for the differences in irrigation demand among the three rice types are the amount and distribution characteristics of rainfall during the rice growth period. In addition, the irrigation demands of rice showed a downward trend as a response to a decrease in ETc and the increase in rainfall in the past 60 years, where rainfall was the dominant factor. With this increasing trend of rainfall and its better and efficient utilization in the future, rice irrigation demands may be further reduced or completely stopped. Under the “double-to-single” cropping pattern, irrigation demand decreased by 16% on average, and the irrigation frequency, as well as the drainage volume burden, were simultaneously reduced.

Canal delivery and irrigation scheduling optimization based on crop water demand

Conventionally, canal water is distributed empirically regardless of soil water status at the time in irrigation districts of China, and the mismatch between the timing of water delivery and crop water demand often leads to the reduction in total production and irrigation water efficiency. In the study, an optimization model with minimizing both the difference between the time of water delivery and water demand, and fluctuation of discharge of the main canal as objectives was developefd for a two-stage canal system. The genetic algorithm was used to solve the problem. The irrigation time to meet the water demand in the optimization model was determined using a field water balance model for the command area of secondary canals. The optimization model was applied to the Xixun irrigation district located at Zhangye, Gansu Province, Northwest China. The performance of the model was evaluated by comparing crop water consumption and water productivity (WP) between optimized with conventional scheduling. The results showed that the optimized scheduling could achieve greater total production, less water loss, higher water use efficiency (WUE) and irrigation water productivity (IWP) under both full and reduced capacity conditions. Specifically, the optimized scheduling led to 20% greater total production, 33% less water loss, and more than 20% larger IWP than the conventional scheduling under both conditions. The optimization model could be a valuable tool in improving WP over the command area by adjusting water delivery and irrigation scheduling for irrigation districts.

Numerical Modeling Applied to Leachate Generation using Hydrus – Case Study: Seropédica, Rio de Janeiro, Brazil

ABSTRACT Improper design and management of the cover layer of a sanitary landfill has been proven to produce harmful environmental impacts on the environment. One alternative at hand is to develop scenarios based on simulation of physical and computational models to represent the expected field water balance of a landfill coverage layer. This paper investigates the design of a sanitary landfill final cover in the municipality of Seropédica, which is located at the state of Rio de Janeiro - Brazil. More specifically, the compact soil coverage, which is widely used for landfill final cover of municipal solid waste, is evaluated in contrast to vegetation cover by grass, vegetation cover by brachiaria and capillary barrier. To accomplish such task, hydrometeorological forcing conditions, namely daily rainfall and temperature, were retrieved from the Anchieta weather station, which is situated nearby the study area. The Hydrus 1D and 2/3 D computational codes were employed to develop a set of scenarios to follow the contamination plume evolution within the landfill along the time frame of 20 years with some degree of reliability. It should be noted that the performed evaluation indicates the possibility to control the leachate release and consequently to avoid contaminating the environment, notably to prevent soil and water resources pollution. Vegetation cover by grass and brachiaria showed important control mechanisms with respect to the movement of the contaminant plume. In addition, it should be noticed that the best results for the landfill final cover were achieved for the capillary barrier, while poor performance results were obtained for the commonly employed compact soil.

Assessment of grey water footprint in paddy rice cultivation: Effects of field water management policies

Excessive use of fertilizers and manure has detrimentally affected surface and ground water resources due to high rates of nitrogen (N) deposition. Reducing the nitrogen-related grey water footprint (GWF) is crucial, otherwise it may lead to severe food production-related water pollution and a reduction in freshwater absorption capacity. This study explored the feasibility of farmland water management policies (WMPs) for GWF regulation in paddy rice fields. Four WMPs—frequent shallow irrigation (FSI), wet and shallow irrigation (WSI), controlled irrigation (CI), and rain-catching and controlled irrigation (RCCI)—were analyzed based on daily field water balance and nitrogen transportation in Nanjing, China. The results showed that GWF varied among the four WMPs. During 2015–2017, the GWF values under FSI, WSI, CI, and RCCI policies were 303.6, 366.4, 369.5, and 218.3 mm, respectively. The GWF under RCCI was the smallest for all the years, that under CI was the highest in the wet year (2016), and that under FSI was the highest in the dry year (2017). GWF increased with an increase in total field water inflow and precipitation. Additionally, changes in the irrigation and drainage methods could regulate and decrease GWF. Pollutant leaching risk increased with rising precipitation, which could be mitigated by reducing drainage in the early stages of growth. In East China, RCCI was observed to be the best policy for managing field water in paddy production with regard to GWF reduction. The findings of this study can aid in agricultural water resource management.

Comparison of Fenugreek Crop Evapotranspiration Measured by a Micro-lysimeter, Field Water Balance Method and Automatic Closed Canopy Chamber

The attempt was to design and develop an automatic closed canopy chamber (ACCC) having dimension of 1.2 m×1.2 m× 1.2 m for crop evapotranspiration measurement by using transparent acrylic sheet of 4 mm thickness. Between two small fans a temperature and relative humidity sensor was used to measure vapor density. The intermediate circuit was developed for making automation system in ACCC. The arduino based coding was developed as per desired logic operation. The top lead of chamber was automatically closed for 2 minutes when inside and outside temperature and relative humidity of ambient air were similar. During measurement mode of ACCC, the two fans were started automatically. After measurement mode, fans were automatically stopped and top lead was opened. The ACCC was calibrated by evaporating mass of water from water filled tray which was placed inside the automatic closed canopy chamber. The validation of the developed ACCC were made using micro-lysimeters (MLS) having size of 0.2 m × 0.2 m × 0.2 m by growing shallow rooted crop like fenugreek. The depth of irrigation was computed based on soil moisture content before irrigation and field capacity. The field testing of ACCC was made by placing chamber in plots of fenugreek crop. The irrigation was applied by drip irrigation as per crop water consumption. The sensor sensed and recorded the instantaneous temperature and relative humidity at 1 second interval for 24 hours. Two sample t-tests were done to compare the data pair of crop evapotranspiration obtained by the MLS inside the ACCC with that of outside the ACCC to ascertain whether there is any effect of the change in micro-climate for a short period of 2 minute on the crop growth physiological processes. Also, the data pair of crop evapotranspiration measured by the MLs, ACCC using the sensor data of temperature-relative humidity were compared and statistically analyzed through t-test. Similarly, the data pair of ETC measured by the FWB (Field Water Balance Method) and ACCC using the sensor data of temperature-relative humidity were also compared and statistically analyzed through t-test. The calibration factor of the ACCC was found as 1.666. The results revealed that there was no significant difference in the crop evapotranspiration measured by the MLs inside and outside ACCC. Also in case of validation and field testing of ACCC, there were no significant difference between the ETC measured by the ACCC, MLs and FWB at 95 percent confidence level. This implies that there are no effects of the change in micro-climate for a short period of 2 minutes in the chamber, on the plant physiological processes. The ETc rate of fenugreek increases as sun rises and reaches the peak after one to two hour from mid-day and then continuously decreases with time. During validation and field testing of ACCC, the fenugreek crop coefficients varied from 0.72 to 1.04 and 0.69 to 1.02 respectively. The developed ACCC is portable as well as more comfortable and cost effective compared to the lysimeter for the measurement of the actual crop evapotranspiration and the crop coefficient.

Elevated temperature and low nitrogen partially offset the yield, evapotranspiration, and water use efficiency of winter wheat under carbon dioxide enrichment

Atmospheric carbon dioxide (CO2) concentration, temperature and nitrogen (N) are the key regulators of productivity and water use of plants under the changing climate. However, field scale studies on the interactive effect of the three above critical inputs are limited. Hence, this field study was conducted with three climate treatments (ambient (AC), elevated CO2 (eC, ~550 µmol mol−1) and co-elevation of both CO2 and temperature (eCeT, ~550 µmol mol−1 and temperature ~2 °C above ambient)) and four N treatments (0%, 50%, 100% and 150% of recommended N dose of 120 kg N ha−1). The experiment was carried out in open top field chambers to study the effects of climate and N application on grain yield, evapotranspiration (ET) and water use efficiency (WUE) in wheat crop. Crop ET was estimated by field water balance method and WUE by taking the ratio of grain yield to crop ET. Elevation of CO2 showed 9% yield gain over ambient (averaged across N levels), whereas, co-elevation of temperature reduced the yield gain to 4%. Further, N application significantly altered the level of CO2 response. Under CO2 enriched environment, the yield gain was 15% with N100 as compared to 2% and 4% under N0 and N50, respectively, indicating CO2 enrichment benefits in grain yield was N dependent. The three years’ pooled data showed significant effect of climate, N and their interaction on profile water storage, evapotranspiration and WUE. Elevation of CO2 alone or with co-elevation of temperature resulted in significant decline in crop ET by 4–11 mm and significant increase in profile soil moisture and WUE. The WUE improved significantly, by 12% under eC and by 4% under eCeT, respectively, with the increase, more attributed to gain in grain yield. Quantitative derivation from the three years’ field experimentation could establish that under elevated CO2 scenario (550 µmol mol−1), an additional 1 °C rise in temperature would result in enhanced crop ET by 5 mm and yield loss of about 4%. This study thus revealed that limited N and increased temperature would potentially restrict the CO2 mediated benefits in wheat yield and water use under the changing climate.