Soil Water Availability Research Articles

Analisis Kesesuaian Lahan Tanaman Padi di Nagari Panampuang Kecamatan Ampek Angkek Kabupaten Agam Berbasis Sistem Informasi Geografi (SG)

This study aims to analyze land suitability for rice cultivation in Nagari Panampuang using Geographic Information Systems (GIS) and the matching method. This method compares land characteristics, such as soil texture, slope, water availability, and climate, with the growth requirements of rice plants. The data used include topographic maps, land use maps, and climate and soil data. The analysis results show that most areas in Nagari Panampuang have varying levels of land suitability for rice cultivation, with some locations recommended for further development. Map overlays indicate that S1 land (Highly Suitable) covers 226 hectares in Jorong Kubu, Surau Labuah, Surau Lauik, and Lurah, with highly supportive conditions. S2 land (Moderately Suitable), covering 17 hectares in Surau Labuah, has minor constraints, while S3 land (Marginally Suitable), covering 116 hectares in Bonjo, Lundang, and Sungai Baringin, has significant limitations. S1 land has the greatest potential, while S2 and S3 lands require more effective management.

Assessing the Impact of Ramularia Leaf Spot on Barley: Prospects for Fungicide Protection Strategies and Weather‐Based Prediction Models in Argentina

ABSTRACTRamularia leaf spot (RLS), caused by the fungus Ramularia collo‐cygni (Rcc), has become a threat to barley production in Argentina and the world, causing grain yield and quality losses. Characteristics of the pathogen such as a long latency period, high evolutionary potential, numerous transposonic regions and the ability to infect alternative hosts facilitate Rcc adaption to environmental changes and/or control measures such as fungicides. RLS is considered a sporadic disease in Argentina and its occurrence is highly dependent on weather conditions. The objectives of this work were to quantify the impact of RLS on grain yield and its commercial quality, to establish an optimal protection period (PP) for barley with fungicides, and to describe the association between environmental variables and levels of RLS with the purpose of designing prediction models and more efficient protection strategies. Based on the results from field trials (n = 8), we estimated grain yield losses up to 16%, and these occurred due to reduced grain weight (8.7%) and size (20%). We also determined that the PP begins from the third detectable node (GS33) to first visible awns (GS49) and concluded that the flag leaf fully emerged stage (GS39) was the most efficient fungicide spraying time. Four possible forecast models were proposed based on the daily average temperature accumulated from early tillering (GS21) to GS39 stage, in combination with the number of days of soil water availability, number of days with water excess and duration of leaf wetness or accumulated rainfall from tillering to GS39 (n = 10).

Biochemical and enzymatic alterations of watermelon associated with irrigation management and inoculation with Rhizobacteria

Water stress has caused major losses in the agricultural productivity of crops, inducing the search for alternatives for sustainable cultivation. In this context, the objective of this study was to evaluate the tolerance of watermelon under water stress, inoculated with bacterial strains of the genus Bacillus spp., regarding the biochemical and enzymatic variables in the flowering stage. A randomized block design was adopted in a split-plot 4x4 factorial scheme, with plots consisting of four levels of soil water availability (40%, 60%, 80% and 100% of field capacity - FC) and subplots consisting of four inoculations (Negative Control (NC); XX6.9 bacteria; P6.2 bacteria; MIX – co-inoculation of XX6.9 and P6.2 bacteria), with five replicates. XX6.9 bacteria and NC were the treatments most affected by severe water stress, since at the soil water availability (SWA) level of 40% FC they showed high contents of the oxidative marker (MDA) and proline. Although the inoculation with XX6.9 bacteria promoted a higher content of osmoregulators such as proteins, total soluble sugars and reducing sugars, it was not enough to attenuate the effects of water deficit. On the other hand, treatments with P6.2 bacteria and MIX of bacteria showed reduced levels of MDA at the SWA level of 40% FC, accompanied by high enzymatic activity of POD and CAT, which may contribute to the tolerance of the watermelon crop to water stress.

Enhancing the water use efficiency model predictions for Platycladus orientalis and Quercus variabilis: Integrating the dynamics of carbon dioxide concentration and soil water availability.

Water use efficiency (WUE) is a tracer for plants on the trade-off exchange of water and carbon dioxide between terrestrial ecosystems and the atmosphere; therefore, a dynamic investigation of WUE and its driving factors will be of great significance to optimize water and carbon fitness and predict the plants' response to climate change. In our study, a modified water use efficiency model was proposed to improve the quantification of carbon and water processes by adding a photosynthesis-gs simulation dependent on CO2 concentration and soil moisture to the photosynthetic transpiration model (noted as SMPTSB model). Actual measured water use efficiencies were respectively obtained by the gas exchange measurements (WUEge) and the δ13CWSC that defined as the carbon-heavy isotope of the water-soluble compound in leaves (WUEwsc) of three-year tree saplings of Platycladus orientalis (L.) Franco and Quercus variabilis Blume, which were cultured in an orthogonal treatment consisting of four ambient CO2 concentrations ([CO2]) and five soil volumetric water contents (SWC). Direct comparisons of the modeled and measured stomatal conductance and WUE further indicated that the modified WUE model makes carbon assimilation, stomatal conductance and WUE more sensitive to [CO2] and soil moisture. From this, the enhancement of WUE in P. orientalis and Q. variabilis saplings is expected to occur when the ambient CO2 concentration increases to 600ppm - 700ppm and the appropriate SWC reaches 60% to 80% of the field capacity for potted soil. In general, the water use efficiency model that accounts for the synergistic effects of environmental CO2 concentration and soil moisture can accurately identify the corresponding thresholds for the optimal efficiency of carbon and water use of vegetation, which is expected to provide a theoretical basis for predicting the corresponding forest management practices to address future climate change.

Drought-Induced Weakening of Temperature Control on Ecosystem Carbon Uptake Across Northern Lands.

Rapid warming in northern lands has led to increased ecosystem carbon uptake. It remains unclear, however, whether and how the beneficial effects of warming on carbon uptake will continue with climate change. Moreover, the role played by water stress in temperature control on ecosystem carbon uptake remains highly uncertain. Here, we systematically explored the trend in the temperature control on gross primary production (measured by "SGPP-TAS") across northern lands (> 15°N) using a standardized multiple regression approach by controlling other covarying factors. We estimated SGPP-TAS using three types of GPP datasets: four satellite-derived GPP datasets, FLUXNET tower observed GPP datasets, and GPP outputs from nine CMIP6 models. Our analysis revealed a significant positive-to-negative transition around the year 2000 in the trend of SGPP-TAS. This transition was primarily driven by synchronized changes in soil water content over time and space. The SGPP-TAS trend transition covered about 32% of northern lands, especially in grasslands and coniferous forests where leaf water mediation and structural overshoot accelerated the drought-induced transition, respectively. In the future, widespread negative SGPP-TAS trends are projected in northern lands corresponding with decreasing soil water availability. These findings highlight the shrinking temperature control on northern land carbon uptake in a warmer and drier climate.

Deficit irrigation differentially modulates rhizosphere microbial community and metabolites of two potato genotypes differing in drought tolerance.

Beneficial interactions between plant root exudates and the rhizosphere microbial community can alleviate the adverse effects of environmental stress on crop yields, but these interactions remain poorly understood in potato growing in drying soil. We investigated the responses of rhizosphere soil microorganisms and metabolites, and biochemical and physiological responses of two potato genotypes with contrasting drought tolerance (drought tolerant 'C93' and drought sensitive 'Favorita'), to two different irrigation treatments imposing contrasting soil water availability in the field. Deficit irrigation altered rhizosphere soil bacterial communities and metabolites of C93 more than Favorita. While the abundance of Nitrosospira and Nitrobacter belonging to the Proteobacteria increased in C93, in Favorita the Streptomyces and Nocardioides belonging to the Actinobacteria increased. These microbial changes were significantly correlated with rhizosphere organic acid concentrations, with 3-phenyllactic acid increasing in C93, and citric acid increasing in Favorita. Although deficit irrigation restricted shoot growth of C93 at the tuber initiation stage (unlike Favorita), its specific root length was 41% greater than Favorita irrespective of irrigation treatment. Deficit irrigation significantly increased foliar chlorophyll and proline accumulation of both genotypes, with the latter 28% higher in Favorita. Independent of irrigation treatment, yield of the more vigorous C93 (producing 22 and 89% more shoot biomass under deficit and full irrigation respectively) was 84% higher than Favorita. It was concluded that different potato genotypes selectively recruit beneficial microorganisms by secreting different organic acids to alleviate the adverse effects of deficit irrigation.

Intensity of Fall-Armyworm (Spodoptera litura Fabricius) pest attacks on Cayenne Pepper (Capsicum frutescens) plants in karst land

Agriculture is an important sector in global food needs. One of the plants that has high economic value in Indonesia is cayenne pepper (Capsicum frutescens). However, the productivity of cayenne pepper is often threatened by pest attacks, one of which is the fall-armyworm (Spodoptera litura), which can cause significant damage to plants. In karst areas such as Ponjong village, Gunung Kidul, Yogyakarta, pest management challenges become more complex due to unique environmental conditions. Karst has calcareous soil and limited water availability, which affects interactions between plants and pests. This research aims to understand the intensity of fall-armyworm attacks on cayenne pepper in karst areas and the environmental factors that influence these attacks. Using survey and field observation methods, this research found that the intensity of pest attacks varied in each plot, with an average percentage of plants attacked at 15.71%. High temperature, humidity and karst soil characteristics create an environment conducive to the development of fall armyworms. Therefore, an effective and sustainable control strategy is needed to support cayenne pepper productivity in karst areas.

Responses of field-grown maize to different soil types, water regimes, and contrasting vapor pressure deficit

Abstract. Drought is a serious constraint on crop growth and production of important staple crops such as maize. Improved understanding of the responses of crops to drought can be incorporated into cropping system models to support crop breeding, varietal selection, and management decisions for minimizing negative impacts. We investigate the impacts of different soil types (stony and silty) and water regimes (irrigated and rainfed) on hydraulic linkages between soil and plant, as well as root : shoot growth characteristics. Our analysis is based on a comprehensive dataset measured along the soil–plant–atmosphere pathway at field scale in two growing seasons (2017 and 2018) with contrasting climatic conditions (low and high vapor pressure deficit). Roots were observed mostly in the topsoil (10–20 cm) of the stony soil, while more roots were found in the subsoil (60–80 cm) of the silty soil. The difference in root length was pronounced at silking and harvest between the soil types. Total root length was 2.5–6 times higher in the silty soil than in the stony soil with the same water treatment. At silking time, the ratios of root length to shoot biomass in the rainfed plot of the silty soil (F2P2) were 3 times higher than those in the irrigated silty soil (F2P3), while the ratio was similar for two water treatments in the stony soil. With the same water treatment, the ratios of root length to shoot biomass of silty soil were higher than for stony soil. The seasonally observed minimum leaf water potential (ψleaf) varied from around −1.5 MPa in the rainfed plot in 2017 to around −2.5 MPa in the same plot of the stony soil in 2018. In the rainfed plot, the minimum ψleaf in the stony soil was lower than in the silty soil from −2 to −1.5 MPa in 2017, respectively, while these were from −2.5 to −2 MPa in 2018, respectively. Leaf water potential, water potential gradients from soil to plant roots, plant hydraulic conductance (Ksoil_plant), stomatal conductance, transpiration, and photosynthesis were considerably modulated by the soil water content and the conductivity of the rhizosphere. When the stony soil and silt soil are compared, the higher “stress” due to the lower water availability in the stony soil resulted in fewer roots with a higher root tissue conductance in the soil with more stress. When comparing the rainfed with the irrigated plot in the silty soil, the higher stress in the rainfed soil resulted in more roots with a lower root tissue conductance in the treatment with more stress. This illustrates that the “response” to stress can be completely opposite depending on conditions or treatments that lead to the differences in stress that are compared. To respond to water deficit, maize had higher water uptake rate per unit root length and higher root segment conductance in the stony soil than in the silty soil, while the crop reduced transpired water via reduced aboveground plant size. Future improvements in soil–crop models in simulating gas exchange and crop growth should further emphasize the role of soil textures on stomatal function, dynamic root growth, and plant hydraulic system together with aboveground leaf area adjustments.

Sugar Content in Arbutus unedo L. Fruit and Its Relationship with Climatic and Edaphic Characteristics.

This research was carried out as part of a program for the conservation and improvement of the strawberry tree. Accessions' prospecting was conducted in different Portuguese provenances. Accessions (204) were identified, and mature fruits were collected in autumn. The sugar contents in the fruit pulp (glucose, fructose, maltose, sucrose) were analyzed by HPLC and the correlation between the average sugar content, climatic classification (Thornthwaite Method and Xerothermic Index), and edaphic characteristics was investigated. The predominant sugar was fructose, which ranged from 7.89 ± 0.55% to 17.01 ± 1.46% (f.w.), respectively, under an Attenuated Thermomediterranean climate at limestone-derived soil and an Accentuated Mesomediterranean climate at schist-derived soil. The lowest sugar contents, linked to a reduction in photosynthesis, were found: (1) in the north, despite soil water availability, due to the low temperature, high precipitation and short photoperiod, particularly during the fruit maturation (autumn); (2) in the south, due to the excessive number of dry days, linked to low soil water availability during the active growth period, particularly at limestone zones prone to water retention. The relationship found between the total sugar content and climate classification by the Xerothermic Index allows to enhance fruit production, advise on the establishment of new orchards and restore natural areas.

Advanced growing-season precipitation peak promotes soil nitrogen mineralization in a semi-arid grassland

Soil nitrogen (N) mineralization is a key process of global N cycling and profoundly regulates plant productivity and soil nutrient pools in the terrestrial biosphere. However, its response to seasonal precipitation redistribution remains largely unexplored. As part of a nine-year (2013–2021) field experiment that simulated advanced and/or delayed growing-season precipitation peaks in a semi-arid grassland on the Mongolian Plateau, this study was conducted for two years (2020–2021) in situ to examine the effects of changing precipitation distributions in the growing seasons on soil mineralization processes. The results showed that advanced precipitation peak (AP) increased soil ammonification (Ramm), nitrification (Rnit), and net mineralization rates (Rmin) by 45.8 %, 26.0 %, and 84.4 %, respectively (all p < 0.001), whereas delayed precipitation peak (DP) enhanced Ramm by 55.7 % (p < 0.001) only, but did not change Rnit or Rmin. The elevated soil N mineralization under the AP treatment could be primarily attributed to the increased soil water availability and microbial biomass N in the early growing season, both of which play essential roles in meditating biological processes in the soil. In addition, the large consumption of soil inorganic N in the early and middle growing seasons may lead to an enhancement of ammonification in September. These observations suggest that advanced rather than delayed growing-season precipitation peak has a stronger influence on soil N dynamics in the growing seasons. Moreover, our findings highlight the positive contributions of altered N transformations to soil respiration and net ecosystem productivity under the AP treatment and imply the crucial roles of intra-annual redistribution of precipitation in regulating ecosystem nutrient and carbon cycling in semi-arid regions.

Responses of soil water supply during the wheat growing season to agricultural management practice in Northern China: A meta-analysis

Context or problemAchieving efficient use of water resources is crucial for ensuring food security in the face of the problems posed by water scarcity and the growing demand for food. Wheat is one of the major crops in the north of China, improving the soil water supply (ΔSWS) through effective agricultural management practices during the wheat growing season is a key strategy to reduce water crises. Objective or research questionThere is much uncertainty regarding the effects of different agricultural management practices (eg. fertilizer practice, mulching practice, irrigation practice, soil amendment or straw returning and tillage practice) on ΔSWS for wheat production. MethodsThis meta-analysis was based on 2523 comparisons in 274 publications from 1999 to 2021 to evaluate the effects of agricultural management practices on ΔSWS during the wheat-growing season in Northern China. ResultsIrrigation and soil amendment practices reduced ΔSWS by 76.95 % and 50.63 %, whereas the wheat yield increased by 21.22 % and 8.86 %, respectively. Fertilizer, tillage, and mulching practices increased ΔSWS by 70.41 %, 32.83 %, 24.6 % and improved wheat yield by 31.1 %, 9.41 %, and 16.26 %, respectively. The effects of different drivers on soil water availability under different agricultural management practices were quantified using linear regression analysis. Irrigation management increased ΔSWS capacity under higher mean annual precipitation, and lower seasonal precipitation, seasonal average temperature, soil pH, seasonal relative humidity, irrigation amounts. Fertilizer practice significantly increased ΔSWS capacity at higher seasonal wind speeds and irrigation amounts. Tillage practice had the best effect on enhancing ΔSWS capacity below 5 °C and lower relative humidity. When the N application less than 210 kg/hm2, seasonal wind speed > 1.31 m/s, seasonal sunshine duration > 900 h, higher seasonal relative humidity and seasonal average temperature conditions, mulching was the best practice to improve ΔSWS capacity. ConclusionsAppropriate agricultural management practices combined with key factors can maximize improve ΔSWS capacity. Implications or significanceThe results provide a reference for fully exploiting ΔSWS capacity using appropriate agricultural management practices under different environment conditions, thereby improving water use efficiency for wheat production in Northern China.

A Decline in Stomatal Conductance Is the Primary Reason for Low Photosynthesis in Veteran Pedunculate Oak Trees

Veteran trees are important elements in forests, as well as urban and suburban areas, and represent part of our cultural heritage. However, increasing age also brings a reduction in vitality. Information on tree physiological vitality can be gained by examining ecophysiological traits, such as photosynthesis, stomatal conductance, and leaf water potential. Here, we assess the effects of age on the photosynthesis and water status of 600-year-old pedunculate oak trees (Quercus robur L.) by comparing them with neighbouring 25-year-old trees. While gas exchange measurements indicated lowered photosynthesis in old trees, their maximum rates of Rubisco carboxylation and electron transport were similar to younger trees, suggesting that biochemical limitations to photosynthesis are not the reason behind their reduced vitality. Moreover, there was no difference in light-adapted and dark-adapted chlorophyll fluorescence between old and young trees. In contrast, stomatal conductance (under unlimited soil water availability) was lower, indicating increased stomatal limitations to photosynthesis in veteran trees. On the other hand, high water potential during mild summer drought conditions indicated better access to soil water in old trees, while stomatal conductance in old trees was higher than in young trees at night. A reduced ability to open and close stomata may be one of the reasons for the observed decline in veteran tree vitality, with a lowered ability to regulate stomatal conductance resulting in reduced carbon gain and unnecessarily high water loss.

A field study integrating plant physiology-soil response for quantifying wilting and plant survival time in a polymer-amended soil

Water deficiency caused by climate change is a global challenge for food security. Viable sustainable alternatives for enhancing water storage in the soil is a necessity for arid and drought prone regions. Water-absorbing polymer (WAP) is capable of improving the water storage in soil pores, and its efficacy can be ascertained by evaluating the resilience of plants towards wilting. The main objective of this study was field demonstration on the usefulness of fly ash-based WAP (FA-WAP) in prolonging wilting and plant survival time of beans (Phaseolus vulgaris) and radish (Raphanus sativus) in a silt loam. This was achieved by following a novel methodology for determining plant permanent wilting point (PWP) by integrating both soil response (suction) and plant response (stomatal conductance and photosynthetic yield), as against the common practice of considering a reference negative water potential (or soil suction) value of 1500 kPa. Using the proposed methodology, the PWP was 1300 kPa and 1150 kPa for beans and radish, respectively. The measured soil water retention curves (SWRC) demonstrated higher water availability in the WAP-amended soil compared to the control soil for both plant species, thereby prolonging plant survival time. The presence of WAP positively influenced the plant biochemical parameters (such as H2O2, MDA, proline, CHL A+B) under water deficit conditions. The WAP amendment resulted in 2.3 and 1.4 times crop yield for beans and radish, respectively, compared to the unamended soil. The use of FA-WAP has a high potential to reduce the irrigation water demand without compromising the yield of two vegetable species considered in this study.

Living on leftovers: biomass management in annual grasslands may shift functional group dominance

Livestock grazing in North American rangelands has the capacity both to promote and control the spread of undesirable plant species. Within California annual grasslands, desirable forage peaks in spring and supports considerable livestock grazing. However, spring grazing appears to promote the invasion and spread of two late-season and unpalatable non-native annual grasses, Aegilops triuncialis and Elymus caput-medusae. We tested the hypothesis that grazing reduces the leaf area and water use of early-spring annuals, thus increasing residual soil water availability for the late-season species. We used grazing-exclosure experiments to examine the interactive effects of simulated grazing (i.e., clipping) and competition on soil moisture availability, and on physiological, phenological, and demographic responses. When compared to unclipped controls, spring clipping significantly increased late-season volumetric soil moisture by 13–24% in the top 7 cm of soil, and 8–11% in the top 20 cm of soil (p < 0.05, all sites), which supported significantly higher rates of stomatal conductance (73–100% increase) in both late-season invading species (p < 0.01, all sites). Flowering was significantly delayed in clipped plots for both invader species suggesting these species experienced a longer growing period (p < 0.0001 in all cases). In competition plots, the effects of clipping on the demographic response depended on neighborhood composition. When invaders were grown together, no significant effect of clipping on survival or reproduction was detected in either invader. However, when growing in mixtures with early-spring forage annuals or native species, clipping increased survival and reproductive output in late-season invader species by 3-fold. We suggest that strategies for arresting or reversing the dominance of these late-season invasive annuals must recognize the influence of current biomass management strategies on late-season resource availability.

Modeling tree responses to soil water variability guides irrigation to account for soil winter reserves

AbstractHigh‐yield almond (Prunus amygdalus) production requires irrigation to support soil water availability throughout the summer. We aimed to develop tools that project almond trees’ water requirements and then integrate them into irrigation management. We postulated that deficit irrigation would limit root allocation and reduce irrigation efficiency. Thus, we monitored soil water availability (soil water content and potential evapotranspiration) and tree physiology (transpiration and trunk circumference) under 600, 900, or 1250 mm summer irrigations. A soil‐tree model was trained to predict trees’ transpiration as the soil dried between irrigation events. The model included an empirical function for tree transpiration at variable soil water potentials (50% loss by −1 MPa). Field records corroborated the soil‐tree model projections that 600 mm irrigation reduces soil water potential to −1 MPa and limits transpiration after winter soil water reserves deplete. Trees at deficit irrigation did grow deep roots to extract soil winter reserves, thus disputing our original notion. A 900 mm irrigation matched transpiration and maintained soil at −0.6 MPa. The 1250 mm irrigation exceeded transpiration and narrowed trees’ water uptake to the upper 50 cm. The reciprocity between soil water and transpiration dictates that predetermined irrigation would limit or exceed transpiration. The soil‐tree model could project transpiration responses to soil water variability, thereby supporting irrigation by trees’ transpiration. The model uses soil water dynamics, rather than insular water potential measures, to account for spatial discrepancies between water application and uptake depths. Hence, the soil‐tree model lays a computational framework for precision irrigation by automated sensory.

Productivity and adaptive properties of different origin potato varieties in the Russia’s Far East south

The paper presents the results of a study on the productivity of potato genotypes of different origin depending on the water availability in soil, including the hydrothermal coefficient of Selyaninov (HTC). The group of mid-season varieties was noted to have the highest productivity (710 g/plant). Waterlogging occurred during the growing period of plants (HTC ≥ 2.5), especially at the stage of tuber formation, negatively affecting productivity. High productivity was observed in the years with relatively favorable weather conditions (2019, 2021, and 2022) when the index of environmental conditions (I) was positive and ranged within +201.63 – +221.35. The average productivity of all the specimens was 950 g/plant. Very low productivity (420–670 g/plant) was observed in 2015–2018, 2020, and 2023 due to waterlogging (I = -99.52 – -269.81). Among the studied specimens, we identified the following varieties that were characterized by not only high productivity (above 900 g/plant) but also high responsiveness to changes in the environmental conditions and stability (average bi = 1.49; S2d·103 = 0.42): early-maturing varieties – Antonina, Bastion, Kolymskii, Krepysh, Matushka, Meteor, Pamyati Kulakova, Udacha, Vitesse, Red Lady, and Red Scarlett; medium-early varieties – Arktika, Briz, Zoya, Kamchatka, Lileya, Charodei, and Gala; mid-season varieties – Ocharovanie, Utro, and Favorit; medium-late and late varieties – Kazachok and Pobeda. The research allowed us to identify potato specimens with high productivity (1040-1480 g/plant), marketability (83.2–92.8%), plasticity (bi = 1.20–1.85), stability (S2d = 0,15–5,77), homeostasis (Hom = 9.51–40.62) and breeding value (Sc = 532.79–852.14) under the conditions of the south of the Russian Far East: early maturing varieties – Bastion, Kolymskii, Krepysh, and Pamyati Kulakova; medium-early varieties – Arktika and Zoya; mid-season variety Alyaska; medium-late and late varieties – Vetraz’ and Pobeda.

Sugarcane bagasse derived biochar potential to improve soil structure and water availability in texturally different soils

Low organic matter content is one of the main constraints in arid and semiarid regions. This constraint and its negative influences on soils and plant growth may be alleviated by biochar (BC). Furthermore, improving soil physical and hydraulic attributes by application of biochar has received increased attention. Therefore, in the present study, the effects of sugarcane bagasse-derived biochar on the structural stability, water availability, and pore-size distribution (PSD) of three texturally different calcareous soils collected from different agro-climatologically regions were examined during a long-term experiment. Low and high-temperature biochars, produced in a muffle furnace by the traditional slow pyrolysis method at 300 °C (BC300) and 600 °C (BC600) were evaluated. Pots (15 kg) were filled with three different silty-clay Inceptisols (SCInc), silty-clay-loam Alfisols (SCLAlf), and loam Aridisols (LArid) soils mixed with 0 (control), 1, 2, and 3 w/w% of BC300 and BC600 during 540 days of incubation. The high energy moisture characteristic (HEMC) data was modeled using a modified van Genuchten function to quantify aggregate stability through stability ratio (SR) and structural stability index (SSI). The plant available water (PAW), least limiting water range (LLWR), and integral water capacity (IWC) were calculated with two matric suctions (h) of 330 cm for field capacity (FC) and 15,000 cm for permanent wilting point (PWP). Then the integral energy (EI) values were calculated (EIIWC). Results indicated that the incorporation of 3 w/w% biochar significantly (p < 0.01) increased SR (35 to 100%) and SSI (21 to 28%) indices in all three soils. Biochar significantly increased modal suction (MS) in LArid soils (5 to 158%); whereas, decreased MS of the other soils (3 to 43%). MS, SR, and SSI of BC300 and BC600-treated soils were not significantly different. PAW, LLWR, and IWC significantly decreased in the SCInc (18 to 61%, 8 to 44%, and 6 to 35%) and SCLAlf (8 to 44%, 18 to 35%, and 20 to 47%) soils and increased in LArid (4 to 54%, 3 to 61%, and 24 to 111%) soil with increasing biochar doses. There were no changes in EIIWC in biochar-treated LArid soil where PAW, LLWR, and IWC increased. Biochar increased EIIWC across the studied soil from 1% to 3.38 folds, thereby increasing the gradient of water potential to absorb the available water. Soil and soil-biochar mixtures exhibited heterogeneous and multimodal pore-size distribution (PSD). Biochar promoted the PSD peaks related to water-transmitting pores in SCInc and SCLAlf soils while decreased in LArid soil. In conclusion, results indicated that among the applied levels of biochar, the application of 3 w/w% biochar is suggested as a suitable way to improve soil physical behavior and structural stability.

Water Use Efficiency Characteristics and Their Contributions to Yield in Diverse Sugarcane Genotypes with Varying Drought Resistance Levels Under Different Field Irrigation Conditions

Drought is the major abiotic constraint affecting sugarcane productivity and quality worldwide. This obstacle may be alleviated through sugarcane genotypes demonstrating good water use efficiency (WUE) performance. This study aims to investigate the WUE characteristics of various sugarcane genotypes under different soil water availability levels. Plant and ratoon field experiments were conducted using a split-plot randomized complete block design with three replications. The main plots were assigned three types of irrigation: (1) rainfed conditions (RF), (2) field capacity conditions (FC), and (3) half-available water (½ AW). The subplots consisted of six sugarcane genotypes with varying levels of drought resistance, i.e., KK3, UT13, Kps01-12, KKU99-03, KKU99-02, and UT12. Data on yield, stalk numbers, stalk diameter, height, and WUE were collected throughout the crop cycle for both plant and ratoon crops. For the plant crop, the net photosynthesis rate, transpiration rate, stomatal conductance, and leaf area index (LAI) were recorded during the crop period. In both plant and ratoon crops, the WUE in the RF treatment was lower than in the FC and ½ AW treatments during the drought stress period 4 months after planting (MAP). In the recovery phase, the WUE in the ½ AW treatment fell between the FC and RF treatments. The RF treatment exhibited the lowest WUE compared to the other two water regime treatments at the maturity stage. The drought-resistant genotypes KK3 and UT13 maintained high WUE values throughout both the drought and recovery periods and exhibited outstanding LAIs at 4 and 6 MAP. A significant relationship existed between WUE and LAI during these periods. Moreover, WUE was positively correlated with cane yields and yield components, such as stalk weight, shoot diameter, and height, during recovery and tiller number and height during ripening. Therefore, WUE and LAI are efficient parameters for supporting and maintaining growth and yield during water deficit and recovery phases under rainfed conditions.

Point of Limited Availability of Water in Soil and Its Determination

Point of Limited Availability of Water in Soil and Its Determination

Do Cover Crops Influence In Situ Soil Water Potential After Termination?

Soil water movement is energy-dependent and is influenced by various management practices. It can be understood by measuring the soil water potential (SWP); however, the influence of cover crops (CCs) on SWP is not currently well understood. The objective of this study was to assess the effects of CCs on SWP before and after termination in order to understand their effects on soil water availability for the subsequent cash crop. The experimental design was a completely randomized design with two levels of CCs (CCs vs. no cover crop [NC]) with three replicates. The SWP sensors were buried at 0–10, 10–20, and 20–30 cm depths before CCs were planted. Additionally, soil samples were collected at the aforementioned depths just before CC termination for soil organic carbon (SOC), bulk density (BD), and saturated hydraulic conductivity (Ksat) analysis. Results showed that CCs increased SOC and Ksat, and significantly lowered BD compared with NC management. Before termination, CC plots had significantly lower SWP values compared with NC management, suggesting that the transpirational needs of the CCs can lead to lower water content. After termination, CC management also resulted in lower SWP, suggesting that CCs can increase water-use efficiency by improving soil health parameters. However, effective planning is required for CC implementation, especially in semiarid and arid regions.