Residual Soil Moisture Research Articles

Drainage estimation across mountainous regions from large-scale soil moisture observations

Drainage is a crucial soil hydrological process that governs the partitioning of rainfall into runoff, groundwater recharge, soil water storage and evapotranspiration. Despite its significance, the drainage process is poorly understood due to the difficulty in direct measurements and insufficient understanding of its underlying physical mechanisms. To address these challenges, we present an innovative, physically-based, data-driven approach, SM2D (Soil Moisture to Drainage), to estimate drainage. SM2D was applied and examined using soil moisture data from a large-scale observation network over mountainous areas during 2014–2020. The soil moisture threshold governing drainage initiation proves to be significantly lower than the commonly employed field capacity metric in hydrological models. This threshold is influenced by factors such as mean soil moisture, bulk density, residual soil moisture, soil organic carbon, and parameters n and α of soil retention curve. Notably, field capacity has minimal impact on this threshold. Additionally, our analysis reveals that the drainage process is more influenced by the Soil Water Storage Increment (SWSI) than by mean soil moisture (MSM) that has traditionally been recognized as a key factor in drainage control. In comparison to commonly used exponential equations and those in models such as the Soil & Water Assessment Tool (SWAT), SM2D demonstrates superior performance in estimating drainage. The exponential equation derived from the SWSI outperforms those derived from other soil moisture metrics, including the commonly utilized MSM, challenging prevailing norms in drainage equations. SM2D holds the potential to generate extensive drainage datasets from satellite or large-scale soil moisture observations, advancing large-scale hydrological studies.

Quantifying Residual Soil Moisture through Empirical Orthogonal Functions Analysis to Support Legume-Based Cropping Systems

AbstractThis study investigates spatiotemporal variability of residual soil moisture during the OND (October-November-December) season in Ethiopia and its implications for crop productivity. Employing advanced statistical techniques, we analyze spatial and temporal distribution of soil moisture across Ethiopia from 1981 to 2020, focusing on selected crops including legumes: chickpea, field peas, common bean, soybean and alfalfa, to assess the potential of residual moisture to support post-rainy season cropping. Results indicate pronounced east-west moisture gradients, with eastern regions of Ethiopia exhibiting lower moisture levels (< 60 kg.m-2) compared to western regions (> 150 kg.m-2). The central highlands, which are pivotal for agricultural activities, demonstrate significant variability in moisture (standard deviations > 25 kg.m-2), with implications on agricultural sustainability. The northern and southeastern tips of the country are particularly vulnerable to prolonged drought, where climate change and frequent dry spells exacerbate moisture deficits, consequently impacting crop productivity. Despite these challenges, promising opportunities for future crop production emerge in the southeastern region, which is characterized by increasing moisture trend over time ($$\:\tau\:=0.59$$). Findings further indicate that residual moisture adequately meets and supports crop water requirements in the western, central, and southwestern Ethiopia. In these regions, residual moisture supports more than 90% of cropland water requirements of various crops during the initial and late-season growth stages, whereas water requirement coverage drops to less than 20% during the mid-season growth stage. Therefore, by utilizing residual soil moisture alongside supplemental irrigation, Ethiopian farmers can meet crop water needs for double cropping and enhance resilience to climate variability.

Modeling the response of crop emergence to sowing depth and soil water deficit in direct-seeded rice

Abstract Background and aims Dry direct seeding of rice in the tropics often suffers from poor crop establishment owing to soil water deficit. A potential solution is sowing deeply to utilize residual soil moisture farther below the surface. We evaluated rice emergence under various sowing depths and soil moisture conditions and tested a model framework of it as a simultaneous function of sowing depth and soil moisture. Methods We combined data from three field experiments and one growth chamber experiment to collect emergence data for four rice cultivars (Dontokoi, Dular, Rc222 and Rc420). We independently parameterized the relationships between emergence and sowing depth or soil water tension using logistic functions. We expressed the final emergence as the product of the two functions. Results Emergence responses to sowing depth and soil moisture fitted the cultivar-specific logistic functions well. For Dular, a cultivar that tolerates deep sowing, emergence was greatest when sown at 4 to 5 cm below the surface under soil water deficit, versus 1 to 2 cm under wet conditions, and our combined model successfully reproduced this result. Conclusion Our emergence model framework supports adjustment of sowing depth to account for available soil water, making the model a powerful new tool for drought adaptation in direct-seeded rice.

Unveiling Genotypic Response of Chickpea to Moisture Stress Based on Morpho‐Physiological Parameters in the Eastern Indo‐Gangetic Plains

ABSTRACTIn the eastern Indo‐Gangetic plains, chickpea is grown postrice cultivation mostly under rainfed condition with residual soil moisture which adversely affects branching as well as pod and seed development, ultimately resulting in substantial yield losses. The current study analysed the moisture stress response of 12 chickpea genotypes with control for different morpho‐physiological traits in two sets of field experiments carried out during the year 2017–18 and 2018–19. The current study observed varying response of chickpea genotypes under moisture stress condition with average yield reduction from 11.79% to 24.77%. Mean yield of genotypes under stress condition showed a strong positive association with yield index (1.00**) and stress tolerance index (0.915**). The biplot principal component analysis revealed maximum potential of three chickpea genotypes (DBGC 1, Pusa 256 and DBGC 2) for grain yield and biological yield under moisture stress condition. The correlation analysis showed a significant association of yield with physiological parameters such as photosynthetic rate (0.363**), stomatal conductance (0.364**) and transpiration rate (0.292*). The three higher yielding genotypes relatively maintained biological yield, yield plant−1, 100 seed weight and photosynthesis rate and showed reduced rates of stomatal conductance and transpiration under moisture stress condition. The study found variable genotypic response to moisture stress and showed that yield index as well as stress tolerance index was more effective to identify superior genotypes for moisture stress condition. The superior genotypes identified in the present study may be considered for rainfed areas of eastern Indo‐Gangetic plains and can be used in future chickpea breeding programs for drought tolerance.

Preliminary Experiences in Determining the Soil–Water Characteristic Curve of a Sandy Soil Using Physical Slope Modeling

Relating soil moisture content to soil suction, the soil–water characteristic curve (SWCC) represents an essential feature in unsaturated soil mechanics that enables estimation of different unsaturated soil property functions and modeling of the macro-scale soil behavior. However, depending on the soil and processes under consideration, proper hydraulic characterization of a soil through direct laboratory measurements can be difficult, time-consuming, and involve many uncertainties. In the case of uniformly graded sands, there is a highly nonlinear and steep shape of the SWCC, with only a few kPa of soil suction separating saturated and residual soil moisture conditions, which makes measurements for determinations of SWCC especially challenging. This study encompasses an investigation of the sandy type of soil’s behavior and presents some preliminary results and experiences on the determination of SWCC through the use of physical slope model tests. The 30 cm deep slope, inclined at 35 degrees and instrumented with soil moisture and pore water pressure sensors, was exposed to series of rainfall intensities, ranging from 37 up to 300 mm/h. The results indicated that the data on hydraulic response in monitored points are not only useful for the determination of SWCC, but that the approach is useful for investigation of hydraulic hysteresis phenomena, as well as its effects on soil moisture and pore water pressure conditions, which also affects the stability conditions of a slope. In particular, the best-fit parameters of the van Genuchten model suggested air entry values of 1.6 and 1.1 kPa for the drying and the wetting curves of the SWCC, respectively, with the two branches shifted by about 1 kPa of soil suction.

Water use and yield response of rainfed safflower (Carthamus tinctorius L.) in Vertisols with varying soil depths

AbstractSafflower (Carthamus tinctorius L.) is an edible oilseed crop mainly cultivated in marginal lands. This study evaluates safflower crop water requirements to understand its feasibility to cultivate under rainfed ecosystem through a field experiment undertaken at the International Crops Research Institute for the Semiarid Tropics research farm, India. Eight improved and stress‐tolerant safflower cultivars (five spiny and three non‐spiny) were evaluated in Vertisols at three soil depths, that is, shallow: <0.60 m, medium: 0.60–1.20 m, and deep:1.20–1.80 m, over 3 years (2009–2012). Wet, normal, and deficit rainfall years were experienced during 2009/2010, 2010/2011, and 2011/2012, respectively. Soil moisture, crop yield, and growth parameters were measured, and field‐scale hydrology was captured through a calibrated one‐dimensional water balance model. Safflower responded to available residual soil moisture which varied with soil depth and rainfall received in different years. Total crop water use was 300–320 mm during the postrainy season, of which about 70% was extracted in deep Vertisols and 55% in medium Vertisols through residual soil moisture. In addition, 30% of water requirement was met through postrainy season rainfall. Safflower grown in shallow Vertisols could only meet 40% of crop water requirement. Spiny cultivar NARI‐H‐15 grown in deep soil recorded a maximum yield of 1890 kg ha−1 in the wet year. Seed yield from spiny cultivars grown in deep and medium soils was nearly similar (1500–1600 kg ha−1) during wet and normal years; a significant reduction in yield (>50%) occurred in shallow soils and also during a rainfall deficit year. Spiny cultivars produced 10%–50% higher seed yield compared to non‐spiny cultivars. Growing safflower in medium and deep Vertisols provides opportunities for crop intensification.

Effect of Sowing Dates and Seed Priming on Agrometeorological Indices and Soil Moisture Regimes of Chickpea in North Central Plateau Zone NCPZ of Odisha

Background: field experiment entitled “Effect of sowing dates and seed priming on agrometeorological indices and soil moisture regimes of Chickpea in NCPZ of Odisha” was conducted at RRTTS, Keonjhar, Odisha, during the Rabi season for two consecutive years i.e., 2021-22 and 2022-23. Method: The field experiment was laid out in factorial RBD design with three replications and two factors. There were 3 dates of sowing in Factor A (D1-25 November, D2-5 December, D3- 15 December) and 5 moisture conservation practices in Factor B (M1- Control, M2- Seed priming with water for 8 hours, M3- Osmopriming (Seed priming with CaCl2 solution @0.5% for 8 hours), M4- Straw mulch@ 5t/ha and M5- Straw mulch@ 5t/ha +Seed priming with CaCl2 solution @0.5% for 8 hours). Seed priming controls the hydration of seeds that helps in the pre germinative metabolic activity of the seeds. So even if the soil has less moisture that will not affect the uniform and proper germination of the seeds. All together there were 15 treatment combinations. The test crop variety taken was JAKI-9218. Among the three dates of sowing, D2 (5th Dec) sowing recorded the tallest plants (41.47 cm). but were recorded in D1 (25 Nov) sowing. Early sowing on 25th November recorded the maximum number of primary and secondary branches and required a greater number of days to 50% flowering (41.8 days) and days to physiological maturity (101.1 days). Results: Among the moisture conservation practices, M5 (Straw mulch@ 5 t/ha+Seed priming with CaCl2 solution @ 0.5% for 8 hours) recorded the tallest plants, maximum number of primary and secondary branches, maximum number of days taken to 50% flowering (40.7 days) and days taken to physiological maturity (100.1 days), maximum number of pods per plant (44) and number of seeds per pod (3.62), grain yield (1812 kg/ha) and straw yield (218 kg/ha). This treatment recorded the minimum consumptive use of water (203.5 mm) and rate of moisture use (1.36 mm/day) but the moisture use efficiency was maximum (12.34 kg/ha-mm). Treatment M5 recorded the maximum growing degree days (2182°C day), heliothermal unit (15077°C day hrs), photothermal unit (22595°C day hrs) and heat use efficiency (0.94 kg/ha/°C) to reach maturity. Chickpea when combined with suitable date of sowing and moisture conservation practices for proper utilization of carry-over residual soil moisture in the rice fallows gives higher yield.

Influence of Weed Management on Weed Dynamics and Nutrient Assimilation by Weeds in Dill (Anethum graveolens L.)

Dill (Anethum graveolens L.) is a minor aromatic seed spice crop grown on residual soil moisture. Since it’s a long duration crop (140-150 days), weed menace is a major problem in it, keeping this in view, a research experiment was conducted during rabi 2020-21 & 2021-22 at MPUAT, Udaipur. The experiment consisted of thirteen treatments that were applied to dill in a three replication randomized block design (RBD). Among the herbicidal weed management treatments, post-emergence (15 DAS) application of oxadiargyl 75 g ha-1 PE fb HW at 40 DAS resulted in the lowest weed density and dry matter of grassy and broadleaved weeds with maximum weed control efficiency at harvest during both experimental years. Further, this treatment recorded lower nutrient uptake by weeds.

Exploitation of the phenotypic diversity of safflower (Carthamus tinctorius L.) for deficit soil moisture stress tolerance

Safflower is an annual oilseed crop grown throughout the semi-arid regions under residual soil moisture. Under the present climatic scenarios, scarcity of water is frequent which is limiting crop yields. A series of field experiments were carried out during post rainy season of 2020-21 and 2021-22 to evaluate the genotype responses to terminal deficit soil moisture stress (DS). The phenotypic data generated in both the seasons revealed that, the huge genotypic difference among the genotypes were conferring tolerance to DS. The PCA analysis revealed that certain morpho-physiological traits viz., plant height, SPAD chlorophyll meter reading, relative water content, and days to 50% flowering accounted for maximum variation under deficit and residual soil moisture conditions.

Enhancement of safflower productivity through improved production technology

Experiment was conducted at Research farm of AICRP on Safflower Research scheme, VNMKV, parbhani. Experiment was conducted in un-replicated manner on 2000 sq. m area of improved technology and farmers’ practice each. Experiment on production potential of and economic effect of improved technologies comprising high yielding PBNS-12 during rabi 2021-22 under residual soil moisture conditions. The additional yield under improved technologies over local practice recorded 1540 kg/ha. In comparison to local practice, there was an increase of 32%. The improved technology with high yielding varieties also resulted in higher benefit cost: ratio of 2.58 with addition returns i.e. Rs. 20736/- over farmer practice.

Sustainable Cropping System Intensification in Arid Region of India: Fallow Replacement with Limited Duration Sorghum–Legume Intercropping Followed by Eruca sativa Mill. Grown on Conserved Soil Moisture

A field experiment was conducted to explore the possibilities of sustainable crop intensification in the fallow–Eruca sativa Mill. system in arid ecology by replacing fallow with short-duration sorghum–legume intercropping. The experiment was laid out in a split-plot design with two planting systems (bed and conventional) in main plots and a factorial combination of crop duration (50 and 60 days) and cropping systems (sole sorghum, sorghum + cowpea, sorghum + Sesbania in 2:2 ratio) in sub-plots. In the succeeding Eruca sativa crop, residuals and two gypsum levels (0 and 250 kg ha−1) were tested. Bed planting practiced during both seasons did not improve the system productivity to significant levels. Extending the duration of fallow replacement crops from 50 to 60 days significantly increased their forage yield, overall system productivity by 25–34%, and system net returns by 15.9–21.5%. Amongst the intercropping systems, the sorghum + Sesbania system added 10–13 tonnes ha−1Sesbania biomass to the soil, resulting in higher soil organic carbon, available nitrogen, dehydrogenase activity, and residual soil moisture, which increased the yield of the succeeding Eruca sativa crop by 8.8–15% compared to the residual of sole sorghum. However, it could not compensate for the yield loss due to the utilization of 50% of the area for growing the green manure crop. The sorghum + cowpea intercropping–Eruca sativa system was found to be the optimum combination with a system productivity of 1.27–1.87 Mg ha−1Eruca sativa seed equivalent. The productivity of Eruca sativa further improved by 9.5–23.7% due to the soil application of gypsum @ 250 kg ha−1. When averaged over treatments, fallow replacement during the rainy season reduced the available soil moisture at the sowing of Eruca sativa by 8.3–22.8% and subsequently its yield by 16.5–30.4% compared to the fallow–Eruca sativa system. However, with this production penalty, an additional rainy-season fodder crop was successfully grown, which improved the system productivity by 57.7–82.8%, net returns by 31.2–57.3%, and rainfall use efficiency from 0.21 to 36 USD/mm−1 ha−1. Hence, it may be concluded that short-duration fodder crops may be taken as fallow replacement crops for higher system productivity and rainfall use efficiency.

Soil moisture observations and machine learning reveal preferential flow mechanisms in the Qilian Mountains

The complexity of the spatial distribution and temporal occurrence of preferential flow (PF) makes it challenging to understand the mechanisms of PF. This study aims to identify the spatial and temporal patterns of PF occurrence using machine learning (Classification and Regression Trees and Random Forests) in the Qilian Mountains, Northwest China. Our results show that detected PF events transport much more rainfall down to the subsoil than non-PF events. Different vegetation types exhibit variations in the main soil layers where PF occurs, which is closely related to the distribution of roots. The PF proportion varies significantly both vertically and horizontally. Based on the Random Forests, we found that the spatial distribution of the PF proportion is mainly controlled by the saturated hydraulic conductivity and residual soil moisture, which cannot be identified by conventional correlation analysis methods. With these soil properties, the spatial distribution of the PF proportion can be estimated with reasonable performance. Using the Classification and Regression Trees method, we identified the temporal occurrence pattern of the PF for different vegetation types and all observation stations. Results indicate that the dominant factors controlling the temporal occurrence of the PF varied for different vegetation types. The thresholds at which these factors initiate the PF also varied. Finally, we found that the PF occurs particularly under wet conditions (except for hydrophobic soils), under denser vegetation, and under conditions of high rainfall amount and intensity, regardless of vegetation type. Our study confirms that both site factors (e.g., soil properties and vegetation) and temporal factors (e.g., initial soil moisture and rainfall characteristics) control the occurrence of the PF in mountainous regions such as the Qilian Mountains and that the Classification and Regression Trees has great potential to study the temporal occurrence of the PF.

Rice-Fallow Targeting for Cropping Intensification through Geospatial Technologies in the Rice Belt of Northeast India

Rice-fallow areas have significant potential to sustainably increase agricultural intensification to address growing global food demands while simultaneously increasing farmers’ income by harnessing the residual soil moisture in rainfed ecologies. Assam is the largest rice-growing belt in northeast India during kharif; however, for the next rabi season, an average of 58% of the rice areas remain uncultivated and are described as rice-fallow (Kharif, rabi and zaid are the crop seasons in the study area. The kharif season refers to the monsoon/rainy season and corresponds to the major crop season in the region extending from June to October. The rabi season refers to the winter season extending from November to April, and the zaid season is the summer crop season from April to June). Unutilized rice-fallow areas with optimum soil moisture for a second crop were identified over three consecutive years using multiple satellite data (optical and radar) for the state of Assam and an average accuracy of 92.6%. The reasons governing the existence of rice-fallow areas were analyzed, and an average of 0.88 million ha of suitable rice-fallow areas, based on soil moisture availability, were identified. Targeted interventions were carried out in selected locations to demonstrate the potential of sustainable cropping intensification. Maize, with best management practices, and a yield between 5.5 and 6 t/ha, was demonstrated as a successful second crop during the rabi season in selected areas with optimum residual soil moisture after the kharif paddy harvest. This study highlights the significance of geospatial technology to effectively identify and target suitable rice-fallow areas for cropping intensification and to enhance productivity and profitability.

GWAS for Early-Establishment QTLs and Their Linkage to Major Phenology-Affecting Genes (Vrn, Ppd, and Eps) in Bread Wheat.

Farmers in northern and central Indian regions prefer to plant wheat early in the season to take advantage of the remaining soil moisture. By planting crops before the start of the season, it is possible to extend the time frame for spring wheat. The early-wheat-establishment experiment began in the 2017 growing season at the Borlaug Institute for South Asia (BISA) in Ludhiana, India, and, after three years of intensive study, numerous agronomic, physiological, and yield data points were gathered. This study aimed to identify wheat lines suitable for early establishment through an analysis of the agro-morphological traits and the genetic mapping of associated genes or quantitative trait loci (QTLs). Advancing the planting schedule by two-three weeks proved to be advantageous in terms of providing a longer duration for crop growth and reducing the need for irrigation. This is attributed to the presence of residual soil moisture resulting from the monsoon season. Early sowing facilitated the selection of genotypes able to withstand early elevated temperatures and a prolonged phenological period. The ideotype, which includes increased photo-growing degree days for booting and heading, as well as a longer grain-filling period, is better suited to early planting than timely planting. Senescence was delayed in combination with a slower rate of canopy temperature rise, which was an excellent trait for early-adapted ideotypes. Thus, a novel approach to wheat breeding would include a screening of genotypes for early planting and an ideotype design with consistent and appropriate features. A genome-wide association study (GWAS) revealed multiple QTLs linked to early adaptation in terms of the yield and its contributing traits. Among them, 44 novel QTLs were also found along with known loci. Furthermore, the study discovered that the phenology regulatory genes, such as Vrn and Ppd, are in the same genomic region, thereby contributing to early adaptation.

The Metabolic Profile of Young, Watered Chickpea Plants Can Be Used as a Biomarker to Predict Seed Number under Terminal Drought.

Chickpea is the second-most-cultivated legume globally, with India and Australia being the two largest producers. In both of these locations, the crop is sown on residual summer soil moisture and left to grow on progressively depleting water content, finally maturing under terminal drought conditions. The metabolic profile of plants is commonly, correlatively associated with performance or stress responses, e.g., the accumulation of osmoprotective metabolites during cold stress. In animals and humans, metabolites are also prognostically used to predict the likelihood of an event (usually a disease) before it occurs, e.g., blood cholesterol and heart disease. We sought to discover metabolic biomarkers in chickpea that could be used to predict grain yield traits under terminal drought, from the leaf tissue of young, watered, healthy plants. The metabolic profile (GC-MS and enzyme assays) of field-grown chickpea leaves was analysed over two growing seasons, and then predictive modelling was applied to associate the most strongly correlated metabolites with the final seed number plant-1. Pinitol (negatively), sucrose (negatively) and GABA (positively) were significantly correlated with seed number in both years of study. The feature selection algorithm of the model selected a larger range of metabolites including carbohydrates, sugar alcohols and GABA. The correlation between the predicted seed number and actual seed number was R2 adj = 0.62, demonstrating that the metabolic profile could be used to predict a complex trait with a high degree of accuracy. A previously unknown association between D-pinitol and hundred-kernel weight was also discovered and may provide a single metabolic marker with which to predict large seeded chickpea varieties from new crosses. The use of metabolic biomarkers could be used by breeders to identify superior-performing genotypes before maturity is reached.

Effects of row spacing on different lentil varieties under strip tillage seeding system

Lentil is an important legume crop grown by three or four time tillage operations with post sowing irrigation after monsoon rice harvest. Strip tillage is a climate smart tillage technology where residual soil moisture can be utilized for plant growth and development. This study was conducted at Regional Agricultural Research Station, Ishurdi, Bangladesh in two consecutive years of 2020 and 2021 to find out the optimum row spacing for specific lentil variety under strip tillage seeding system. Four row spacing (S1= 20 cm, S2= 25 cm, S3= 30 cm, S4= 40 cm) and three varieties of lentil (V1= BARI Masur-8, V2= BARI Masur-7, V3= BARI Masur-6) were assigned in a factorial Randomize Complete Block Design with three replications. The trend of lentil seed yield was recorded as BARI Masur-8 > BARI Masur-7 > BARI Masur-6 and seed yield decreased with increasing row spacing for all varieties. The results showed that 25 cm row spacing for BARI Masur-8, 20 cm row spacing for BARI Masur-6 and BARI Masur- 7 were found suitable row spacing at strip tillage seeding systems. Among the lentil varieties, BARI Masur-8 showed better performance than others due to higher yield attributes and seed yield. Bangladesh J. Agri. 2022, 47(2): 97-106

Circulation and Soil Moisture Contributions to Heatwaves in the United States

Abstract Extreme heat events are a threat to human health, productivity, and food supply, so understanding their drivers is critical to adaptation and resilience. Anticyclonic circulation and certain quasi-stationary Rossby wave patterns are well known to coincide with heatwaves, and soil moisture deficits amplify extreme heat in some regions. However, the relative roles of these two factors in causing heatwaves is still unclear. Here we use constructed circulation analogs to estimate the contribution of atmospheric circulation to heatwaves in the United States in the Community Earth System Model version 1 (CESM1) preindustrial control simulations. After accounting for the component of the heatwaves explained by circulation, we explore the relationship between the residual temperature anomalies and soil moisture. We find that circulation explains over 85% of heatwave temperature anomalies in the eastern and western United States but only 75%–85% in the central United States. In this region, there is a significant negative correlation between soil moisture the week before the heatwave and the strength of the heatwave that explains additional variance. Further, for the hottest central U.S. heatwaves, positive temperature anomalies and negative soil moisture anomalies are evident over a month before heatwave onset. These results provide evidence that positive land–atmosphere feedbacks may be amplifying heatwaves in the central United States and demonstrate the geographic heterogeneity in the relative importance of the land and atmosphere for heatwave development. Analysis of future circulation and soil moisture in the CESM1 Large Ensemble indicates that, over parts of the United States, both may be trending toward greater heatwave likelihood.

Assessing the energy and water balance dynamics of rain-fed rooibos tea crops (Aspalathus linearis) under changing Mediterranean climatic conditions

Rooibos (Aspalathus linearis), a herbal tea crop and a member of the plant family Fabaceae, grows in a narrow ecological range under Mediterranean conditions in South Africa's fynbos biome. There is growing uncertainty on the sustainability of rooibos production under rain-fed conditions in a region which is expected to get warmer and drier in future. No accurate quantitative information currently exists on how the water use, growth and yield of this crop is affected by environmental factors, especially climate and soils. This paucity of data reduces the ability of farmers to develop effective strategies to cope and adapt to the negative effects of climate variability and change. The aim of this study was to investigate the seasonal changes in the energy and water balance of rooibos fields and to establish how this relates to crop yield. An open path eddy covariance system was used to quantify the actual evapotranspiration (ETa) and energy balance components over two growing seasons while sap flow was monitored using stem heat balance sap flow gauges. These data were used to develop and test a simple ETa and yield model which was applied to estimate changes in crop water use and yield under the predicted future climatic conditions. More than 36% of the annual total ETa (∼ 338 mm) was consumed during the first three months of the growing season (September to November) driven by residual soil moisture from the winter rains. Crop transpiration accounted for only 16% of ETa early in the growing season rising to almost 100% during the summer dry months. Daily peak transpiration at maximum canopy cover barely reached 1.0 mm suggesting that this crop uses very little water. Six climate change models were used to simulate crop water use and yield for the far future under the RCP 8.5 emission scenario. All the models predicted increases in both the annual ETa and yield by between 8% and 16% in the period 1961–2099. This study reveals that implementing water conservation and weed management practices early in the growing season can save substantial amounts of soil moisture which can sustain rooibos production under low rainfall conditions.

Evaluation of weed management practice in rice fallow blackgram to manage Vicia sativa in farmers fields in Visakhapatnam district of North Coastal Zone of Andhra Pradesh

Blackgram is major predominant crop during Rabi in Visakhapatnam district of Andhra Pradesh, cultivated in an area of 7,000 ha, out of total cropped area of 75,273 ha with productivity of 300 kg/ha. Farmers grow crop by adopting traditional method of cultivation in rice fallow situation, before harvesting of paddy fields blackgram seed broadcasted and crop is grown with residual soil moisture and nutrients. Among these factors, occurrence of weeds including re-growth of rice stubbles is one of the important factors during early stages as the weeds compete for scarce soil moisture and nutrients. Since, the black gram is sown under zero till condition, weed growth is severe and effectively competes with the crop. To manage the weeds and to increase the yield of rice fallow blackgram, post emergence chemical weed management with sodium acifluorfen 16.5% and Clodinafop-propargyl 8% EC with dosage of 1000 ml/ha ensured effective control of both dicot and monocot weeds in black gram introduced by DAATT Centre, Visakhapatnam district of ANGRAU, in collaboration with KVK, Kondempudi and Department of Agriculture. Chemical weed management method is boon to farmers by controlling the weeds helps in increasing the availability of residual moisture and nutrient to blackgram crops than normal method. Organized an On-Farm Demonstrations (OFDs) in 6 locations randomly covering entire district in Rabi,2018-19 and Rabi, 2019-20. Grain yield increase was achieved to a tune of 31.34% in chemical weed management method (714 kg ha-1) over normal method of cultivation (544 kg ha-1). The increase in grain yield could be attributed to reduction in weeds, helped in more availability of nutrients and moisture which intern increase in yield attributes and yield.

Juvenile heat stress tolerance in Triticum durum-Aegilops tauschii derived synthetics: a way forward for wheat improvement.

Exponentially increasing population and everchanging climatic conditions are two major concerns for global food security. Early sowing in the second fortnight of October is an emerging trend with farmers in Indo Gangetic Plains to avoid yield losses from terminal heat stress. This also benefits the use of residual soil moisture of rice crop, conserving about one irrigation. But most of the available wheat cultivars are not well adapted to early-season sowing. Two in-house developed SHWs, syn14128 and syn14170, were screened for juvenile heat stress. Seedling length, biochemical parameters, and expression of amylase gene immediately after heat shock (HS) of 45°C for 12h and 20h, and 24h indicated significantly lower malondialdehyde, hydrogen peroxide, and higher free radical scavenging activities. Syn14170 reported higher total soluble sugar (TSS) under both HS periods, while syn14128 had a sustainable TSS content and amylase activity under HS as well as the recovery period. Both the SHWs had lower oxidative damage along with high free radical scavenging under heat stress. The higher expression of amy4 along with sustainable TSS after heat stress in syn14128 indicated it as a potential source of juvenile heat stress tolerance. Variable response of SHWs to different biochemical parameters under heat stress opens future perspectives to explore the enzymatic pathways underlying these responses.