Semi-arid Tropics Research Articles

Bi-cropping of castor bean and nutri-millets optimizes system productivity, energy efficiency, and carbon footprint in rainfed alfisols of semi-arid tropics

Intercropping enhances diversity, productivity, resilience, and soil health. To achieve these benefits of the intercropping system, drilling patterns and species mixture play a key role. Therefore, to optimize the productivity, profitability, energetics, and carbon footprint of the castor-based millet intercropping system, a field experiment was conducted for two consecutive kharif seasons (2020 − 2021 and 2021 − 2022) at the University of Agricultural Sciences, Bangalore, Karnataka (India). The results revealed that all the crops under monoculture outperformed their intercropping system for seed and stalk/stover yield. Among the different cropping systems, castor + finger millet (2:4) showed highest castor equivalent yield (CEY; 1911 kg ha−1) due to excellent land utilization efficiency (LUE; 106%), land equivalent ratio (LER; 1.13), land equivalent co-efficient (LEC; 0.32) compared to other cropping systems. Castor + finger millet (2:4) was even found superior in terms of monetary returns. Finger millet monoculture showed the highest energy consumption (10,770 MJ ha−1), energy output (96,507 MJ ha−1), and also net energy gain (85,737 MJ ha−1) compared to other cropping systems. However, it was comparable with castor + finger millet (2:4) despite its modest energy consumption (10,530 MJ ha−1). Castor monoculture showed the highest carbon (C) emission (2045 kg CO2-eq. ha−1) and also C output (1760 kg CE ha−1). While, net C gain (1210 kg CE ha−1), C efficiency (3.39 kg kg−1 CE), and C stability index (2.39) were highest in the castor + finger millet intercropping system. Consequently, the adoption of a castor + finger millet (2:4) intercropping system will be a viable alternative for achieving enhanced system productivity, and energy efficiency with lower C-footprints under semi-arid regions.

Effect of weed management practices on growth dynamics and productivity of rainfed pearl millet under conservation agriculture

An experiment was conducted on rainfed pearl millet at ICAR- IARI, New Delhi, during the kharif season of 2019, in a split-plot design with three replications. Three tillage practices, viz. Conventional tillage (CT), Zero tillage and Zero tillage + Residue@ 3t/ha (ZT+R) were evaluated in the main plot and seven weed management treatments, viz. weedy check, hand weeding (HW) at 30 and 50 days after sowing (DAS), atrazine @ 0.75 kg/ha(PE) fb 2,4-D @0.75kg/ha (PoE), atrazine @ 0.75 kg/ha PE, atrazine @ 0.75 kg/ha PE fb tembotrione @ 0.05kg/ha PoE, atrazine @ 0.75kg/ha PE fb tembotrione @ 0.075kg/ha PoE, atrazine @0.75 kg/ha PE fb tembotrione @ 0.10 kg/ha PoE. ZT+R 3t/ha resulted in enhanced growth attributes, and higher NPK uptake which led to increased grain yield. Among weed control treatments, hand weeding (HW) twice at 30 and 50 DAS along with the integration of pre-emergence application of atrazine 0.75kg/ha fb 2,4-D 0.75kg/ha PoE and tembotrione, 0.075 kg/ha or 0.1 kg/ha PoE resulted in better growth attributes which significantly resulted in higher grain yield under rainfed conditions of semi-arid tropics.

Modeling the influence of small reservoirs on hydrological drought propagation in space and time

To increase drought preparedness in semi-arid regions across the world many small and medium reservoirs have been built in recent decades. Together these reservoirs form a Dense Reservoir Network (DRN) and its presence generates numerous challenges for water management. Most of the reservoirs that constitute the network are unmonitored and unregistered, posing questions on their cumulative effects on strategic reservoirs and water distribution at watershed scale. Their influence on hydrological drought propagation is thus largely unexplored. The objective of this study is then to assess DRN effects on droughts both in time and space. A modeling-analytical framework is proposed to achieve this goal. A mesoscale semi-distributed hydrological model was utilized to simulate both a network of large strategic reservoirs and a DRN in a large-scale tropical semiarid watershed. To investigate the effects in time and space generated by the network’s presence, the differences between multiple network scenarios were analyzed. Results show that the presence of the DRN accelerates the transition from meteorological to hydrological drought phases by 20% on average and slows down the recharge in strategic reservoirs by 25%, leading to a 12% increase of periods in hydrological drought conditions in a highly strategic basin and 26% without strategic reservoirs. This is because the DRN increases the hydrological dysconnectivity at catchment scale, reducing inflow to strategic reservoirs. In space, the DRN shifts upstream the basin’s water storage capacity by 8%, but when both large and small reservoirs are present the stored volume distribution behavior is not straightforward. The findings confirm the need to consider the effect of small reservoirs when developing and implementing drought management policies and reservoir-management approaches at regional scale.

Improving grain quality and nitrogen use efficiency of cereal-based cropping systems on vertisols in semi-arid tropics

ContextSemi-arid tropics is facing serious issues of malnutrition in population owing to poor quality of food grain production. Malnutrition is directly linked to lower grain protein and zinc yield due to inappropriate land and water, and nutrient management practices, which also resulted into reduced nitrogen use efficiency (NUE) in cereals. ObjectiveThe objectives of the study were to evaluate the effect of land and water and nutrient management on grain protein and zinc yield, and NUE of cereal-based cropping systems on vertisols soils in semi-arid tropics. MethodsThe study was carried out at Hyderabad in India during 2014–15 and 2015–16 and involved three cropping systems (two rotation systems: sorghum-chickpea and maize-groundnut; and one intercropping: pearl millet + pigeonpea), two land and water management i.e. flatbed and broad bed furrows and four nutrient management-N1: Control (no fertilizer), N2: 100% recommended application of macronutrient (nitrogen, phosphorus and potassium) through chemical fertilizer, N3: N2 + 100% recommended application of secondary nutrient (sulphur) and micronutrient (zinc and boron) through chemical fertilizer, and N4 (integrated nutrient): 50% of N2 + 50% nitrogen in cereals or phosphorus in legumes through organic fertilizer as vermicompost. ResultsIn sorghum-chickpea rotation system, the treatment interaction broad bed furrows with 100% recommended application of macronutrient, secondary nutrient and micronutrient recorded significantly higher grain zinc yield in both the years, while grain protein yield was significantly higher in second year. The grain protein and zinc yield in sorghum-chickpea rotation system, and agronomic nitrogen use efficiency in pearl millet+pigeonpea intercropping system was significantly higher in broad bed furrows than flatbed. The agronomic NUE of broad bed furrows was higher by 61% in 2014–15 and 65% in 2015–16 over flatbed. Among the nutrient management treatments, grain protein and zinc yield, and agronomic NUE were significantly higher in combined application of macronutrient, secondary nutrient, and micronutrients through chemical fertilizer i.e. N3 followed by N4, N2 and N1. ConclusionThe broad bed furrows and application of macronutrient, secondary nutrient and micronutrient could be an effective integrated land and water and nutrient management approach to improve grain quality and agronomic nitrogen use efficiency of cereal-based cropping systems in semi-arid tropics. ImplicationsThis study contributed to develop integrated land and water and nutrient management as an innovative agronomic management practice for cereal-based cropping systems, which needs to scale-up through Government agricultural policies to overcome the issue of malnutrition in population living in semi-arid tropics.

Can natural undisturbed revegetation restores soil organic carbon to levels under native climax vegetation under tropical semiarid climate?

AbstractLand‐use change has driven soil carbon stock losses in ecosystems worldwide. Implementing agricultural crops and exploiting forest resources trigger the breakdown of soil aggregates, thus exposing organic matter to microbial decomposition and enhancing carbon dioxide emissions, especially in biomes more susceptible to climate extremes as in the tropical semiarid regions. This study was based on the hypothesis that the undisturbed soil from the dry forest (Caatinga biome under natural revegetation in Brazilian semiarid) would have an improvement in the mass of macroaggregates and recover more than 50% of the soil C stock within 10 years. Thus, a field experiment was conducted to investigate soils from the Caatinga biome under native vegetation, “cowpea cropping” for over 30 years, and soil under natural revegetation for over 10 years, after conventional soil cultivation of maize and cowpea, to determine soil and soil‐aggregates carbon stocks and to estimate the recovery rate of these stocks. The proportional mass of aggregates of different sizes and the total stock of particulate organic carbon (POC) were also quantified. The results showed that soil under preserved native vegetation of dry forest Caatinga biome had higher total soil C stock (50.9 Mg ha−1) than that under cowpea cropping (23.2 Mg ha−1) and natural revegetation (45.1 Mg ha−1). The proportional mass of large macroaggregates was higher in soil under native vegetation for all depths. However, soil under cowpea cropping had lower C stocks in macroaggregates, and recovered roughly 63% of the original C stocks, while revegetation recovered 78% of the stock in 10 years. Although the conventional management system for cowpea monoculture aggravated losses in soil carbon stock by more than 50% of the original C stocks, dry forest under natural revegetation recovered 79% of this stock and almost 100% of POC stock in 10 years (~12 Mg ha−1). Furthermore, soil under undisturbed Caatinga dry forest achieved C stock levels equivalent to that of the global average range for semiarid tropical environments. The high recovery rate of C stock in forest soil under natural revegetation indicates the resilience potential of organisms responsible for structural protection of aggregates and the encapsulated soil organic matter content.

Palygorskite in Indian tropical soils: a clay mineral of pedogenic, geogenic, or climate-induced origin – a mechanistic review

Abstract Most clay minerals are characterized by a platy morphology. By contrast, palygorskite has a fibrous morphology and is structurally distinct from the typical 1:1 and 2:1 layer structures. Diverse opinions exist on the origin of palygorskite in soils. Many authors suggest that palygorskite forms after smectite. Others favor its authigenesis during pedogenic processes or its inheritance from the parent material. This review provides a critical synthesis on the origin of palygorskite in the semi-arid-tropical (SAT) Vertisols and arid calcic soils of the Thar Desert of India. It also highlights the specific genetic pathway for the presence of palygorskite in the soils. The ubiquitous association of smectite with palygorskite is inadequate to explain the formation at the expense of smectite, because at pH 8.2 and above the smectite structure is subjected to dissolution to create soluble Si and Al, and the recrystallization of the soluble Si and Al to form palygorskite may not be possible in the Vertisols of the Indian SAT environment. Thus, mildly to moderate alkaline pedochemcial environments of the SAT Vertisols do not favor authigenic precipitation of the palygorskite in such soils. This review shows that the presence of palygorskite in the SAT Vertisols is due to its inheritance from the exhumed inter-trappean beds, infra-trappean beds, and bole beds. This view on the genesis of the palygorskite is also justified by its presence in weakly developed calcic soils of the Thar Desert as detrital flux from the adjoining marine sedimentary rocks.

Traços funcionais dos Nematoda são uma boa ferramenta para visualizar uma sucessão ecológica em substratos artificiais em um reservatório do semiárido brasileiro?

Abstract Aim The Brazilian tropical semiarid is a biome with small freshwater ecosystems, often intermittent, acting as a mosaic in constant transformation between dry and rainy seasons. Meiobenthic communities play crucial roles in these environments, and understanding their colonization and succession processes is essential to comprehend how these organisms’ structure in a defaunated habitat. In addition to the traditional taxonomic approach, functional traits provide valuable insights into the dynamics of these processes. In this study, we tested the following hypotheses: i) although meiofauna consists of microscopic organisms with limited active dispersion, they quickly colonize new substrates, increasing in abundance, richness, and diversity; ii) functional traits of freshwater Nematoda are a good tool for view an early succession on hard artificial substrate in a lentic reservoir. Methods We placed 27 ceramic plates in a reservoir in the Brazilian semiarid and randomly sampled three replicates each week over nine weeks. Weekly differences in community abundance, richness, and diversity were tested with one-way ANOVA and pairwise PERMANOVA. Results Nematoda predominated in the first week, with Rotifera taking over from the second week of the experiment. No differences were observed in the Nematode taxonomic structure over the weeks. There was an increase in the functional complexity of the Nematoda community over time, as indicated by the maturity index and trophic structure. Colonizers/persistents emerged quickly in the first week. Deposit feeders dominated, but an increase in trophic diversity was observed with the growing presence of chewers over the weeks. Conclusions This study highlights that the functional traits of Nematoda represent a robust tool for assessing ecological succession in freshwater lentic environments in the tropical semiarid.

Variáveis ambientais como preditoras da assembleia de peixes em sistemas aquáticos semiáridos

Abstract Aim To understand the distribution of fish species and their use of habitat, a range of environmental variables were evaluated as predictors of fish assemblage composition and richness in tropical semiarid aquatic systems. Methods We surveyed the species composition of fish assemblages in semiarid aquatic systems and established their degree of association with the structure of the aquatic habitat. Sites consisted of stream reaches with surface water flow, isolated temporary pools, and man-made reservoirs. Fish sampling was conducted on four occasions during the wet (April and June 2006) and dry seasons (September and December 2006). The correlation between richness and abundance with the habitat structure was evaluated using stepwise multiple regression. Patterns of variation in fish assemblage composition across sites were evaluated using Nonmetric Multidimensional Scaling, and the Indicator Species Analysis was used to determine which species were significant indicators of sites. To establish multivariate correlations and test the hypothesis of local fish composition being associated with the environmental variables we used a Canonical Correspondence Analysis. Results Morphometric variables, stream reach width, stream length and elevation explained 75.6% of the variation in fish richness. Macrophyte cover and overhanging vegetation added to the predictive power of the model equation, where the final model explained 86.9% of the variation in fish richness. Canonical Correspondence Analysis showed a significant relationship between fish composition data and site morphology (altitude, bank slope and littoral depth). Among the water quality, habitat composition and substrate variables, temperature, sand, and gravel showed higher correlation with the CCA axes. Conclusions These results indicated that fish communities assume different structures and compositions across different habitat types following the environmental heterogeneity in dryland aquatic systems.

Ajwain (Trachyspermum ammi L. Sprague) based intercropping for higher system productivity of semiarid tropics of Northern Karnataka

Ajwain (Trachyspermum ammi L. Sprague) based intercropping for higher system productivity of semiarid tropics of Northern Karnataka

Seasonal occurrence of major defoliators of castor in Tamil Nadu

Castor is a non-edible oil bearing crop adapted to dry lands of tropics and semi-arid tropics. The seasonal occurrence of major defoliators viz., semilooper, Spodoptera and hairy caterpillars in castor was recorded continuously for last ten years (2012-2022) at Tapioca and Castor Research Station, Yethapur. The results revealed that Spodoptera litura was the major defoliator with a mean population of 4.3 larva/plant /year followed by semilooper and hairy caterpillar with 1.74 larva/plant/year and 1.44 larva/plant/year respectively. The maximum population of defoliators was recorded every year during 43rd to 49th standard weeks (October, November).

Comparative assessment of farmers’ perceptions on climate change: Experiences from semi-arid tropics of India

The present study was conducted to assess farmers' perceptions of the effects of climate change on their livelihoods. The aim was to compare these perceptions regarding climate trends, related effects, and adaptation options among rural communities in three Semi-Arid Tropical (SAT) villages located in Maharashtra and Andhra Pradesh, representing different agro-ecological regions. This study employed both quantitative and qualitative research methods to elicit farmers' perceptions, including farm household surveys, focus group discussions, and key informant interviews. The results of the study indicate that farm households are aware of climate change and are particularly concerned about changes in rainfall patterns and increased frequency of drought events, both in inter-seasonal and intra-seasonal distribution. Among the studied villages, Dokur experienced the most severe impacts from these changes. Furthermore, farmers perceive that natural resources such as land, water, and biodiversity have been affected due to the variations in the climate. In response to these challenges, farmers have adopted a set of adaptation options, including changes in crop selection, land management, water usage, socio-economic strategies, and collective actions. However, the study found discouraging trends in the adoption of these adaptation options, primarily due to a range of barriers that hinder their ability to adapt efficiently to climate change. This study underscores the critical need for region-specific strategic research and development programs aimed at enhancing the biophysical and socioeconomic conditions of these rural areas. Such efforts would enable these communities to improve their adaptive capacity and livelihood resilience in the face of climate-related risks and impacts. Future policies and programs should prioritize the upliftment of these fragile SAT communities, with the goal of enhancing their resilience to climate change and improving their overall quality of life.

Anti-nutrient composition of starch isolated from red and white sorghum cultivars subjected to different steeping times.

Sorghum (Sorghum bicolor) is a staple food that provides a major source of calories to large segments of the population living in semi-arid tropics of Africa and Asia. Steeping is an age-long process among all the available food processing techniques known to improve nutritional qualities, palatability and consumer appeal of sorghum. The effects of steeping periods on the anti-nutrient composition of starches from two varieties of sorghum (red and white) were investigated. Sorghum grains steeped for 6, 12, 18 and 24 h with water were processed into starch and sample from unsteeped sorghum served as control. The starch samples were analysed for anti-nutrients components using standard analytical procedure. Anti-nutrients investigated varied with cultivars and increased steeping time. Hydrogen cyanide observed was in the range of (1.34 to 1.86 mg/kg), tannin (1.30 to 4.82 mg/g), saponin (6.10 to 13.05 mg/g), oxalate (0.43 to 0.90 mg/g), phytate (2.15 to 9.06 mg/g), cardiac glycoside (9.30 to 13.35 mg/g), terpenoid (13.50 to 18.99 mg/g) and alkaloid (34.10 to 50.31%). The objective is to determine the anti-nutrients composition of starch from red and white sorghum. There was no significant difference between starches from the two cultivars of sorghum (red and white) in most of the parameters investigated. However, the red cultivar recorded higher values in some of the anti-nutrients investigated. The anti-nutrient levels significantly reduce with increase in steeping time thereby improving the bioavailability of mineral and other nutrients present in sorghum. Mixture of two varieties (red and white) could find applications in food formulations.

Nutritional, phytochemical, and safety profiling of Senegalia seeds, promising wild legumes in the arid and semi-arid tropics

This study presents the chemical composition of seven representative Senegalia (new Acacia s.l. segregate genus) seed species and discusses their food potential and safety. As shown, most of the analyzed seed species demonstrate unique chemical compositions, i.e., very low starch (<0.63 g/100 g dm (i.e., detection limit)) and glucose (1–2 g/100 g dm), high neutral detergent fibers (16–20 g/100 g dm), moderate protein (sum of amino acids) (10–20 g/100 g dm) and nucleic acid polymers (5.3–8.9 g/100 g dm), variable lipid (6–12 g/100 g dm), ash (3.3–4.9 g/100 g dm), phenolic compounds (741–1618 mg GAE/100 g dm), tannins (266–1230 mg TAE/100 g dm) and phytate (299–746 mg PAE/100 g dm) contents, and a relatively balanced amino acid composition. In addition, the seeds have revealed variable contents of trypsin inhibitors (18–45 TIU/mg dm), lectin-related proteins, unidentified non-protein amino acids, hemolytic activities, and cyanogenic glycosides (3.5–11.9 mg cyanide/100 g dm), contrasting their nutritional values and food safety. Despite the considerable effort to comprehensively and accurately determine the chemical composition of the seeds, a large mass fraction (37–44 g/100 g dm) remained unresolved, illustrating the challenge in unconventional food matrices analysis. Nevertheless, distinct compositional profiles between the seed species of the different Senegalia infrageneric sections (i.e., Senegalia section Senegalia and Senegalia section Monacanthea) were uncovered, inviting further investigation on the influence of the infrageneric segregation on the seed compositional properties and food safety.

Exploiting Indian landraces to develop biofortified grain sorghum with high protein and minerals.

Sorghum (Sorghum bicolor L. Moench) is the staple cereal and is the primary source of protein for millions of people in Asia and sub-Saharan Africa. Sorghum grain value has been increasing in tropical countries including India owing to its gluten-free nature, anti-oxidant properties and low glycemic index. However, the nutrient composition of modern cultivars is declining thus necessitating genetic biofortification of sorghum to combat malnutrition and improve nutritional balance in the human diet. Keeping this in view, efforts were made to utilize valuable alleles, associated with nutrient composition, that might have been left behind in the varietal development in sorghum. The study aimed to determine the genetic improvement for nine nutritional and quality parameters (crude protein, in vitro protein digestibility (IVPD), total iron (Fe), total zinc (Zn), bioavailable Fe (%), bioavailable Zn (%), total phenolics, tannins and antioxidant activity) in the grains of 19 sorghum genotypes (high yield, drought and grain mold tolerant) developed from 11 superior India's landraces. After selection and advancement made from 2017 to 2022 through single seed descent method, the improvement in the nine nutritional and quality parameters was assessed. Significant variation was observed for all the nine parameters among the landraces and the genotypes. Sorghum genotypes PYPS 2 and PYPS 13 recorded the highest crude protein (13.21 and 12.80% respectively) and IVPD (18.68 and 19.56% respectively). Majority of the sorghum genotypes recorded high Fe (14.21-28.41 mg/100 g) and Zn (4.81-8.16 mg/100 g). High phenolics and antioxidant activity were recorded in sorghum genotypes PYPS 18 (85.65 mg/g gallic acid equivalents) and PYPS 19 (89.78%) respectively. Selections through SSD method revealed highest improvement in genotype PYPS 10 for crude protein (32.25%), total phenolics (18.48%) and antioxidant activity (15.43%). High improvements in genotypes PYPS 12 (23.50%), PYPS 3 (26.79%), PYPS 15 (21.18%) were recorded for total Fe, available Fe and high tannins, respectively. The study demonstrated that landraces could be effectively utilized as a potential, low-cost and eco-friendly approach in sorghum genetic biofortification to improved sorghum productivity and nutritional supply in semi-arid tropics.

Assessing Groundnut (Arachis hypogaea L.) Genotype Yields and Yield Traits with Different Planting Geometries on Broad Bed and Furrows

A field study on “Assessing Groundnut (Arachis hypogaea L.) genotype yields and yield traits with different planting geometries on broad bed and furrows” was conducted during rabi season of 2022 in the experimental field at International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Hyderabad, Telangana. The experiment was laid out in factorial randomised block design with three replications. Total 16 treatment combinations consisted of four planting geometries (P1) 30 × 10 cm, (P2) 15:15 × 10 cm, (P3) 20:20 × 10 cm, (P4) 25:25 × 10 cm and four varieties (V1) Girnar 4, (V2) Girnar 5, (V3) Avtar, (V4) K6. The important findings emerged from this investigation found that groundnut sown at the spacing of (P4) 25:25 × 10 cm recorded significantly higher number of pods plant-1 (33.0), kernels pod-1 (2.0), test weight (38.7 g), shelling percentage (67.1%), pod yield (1792 kg ha-1) followed by (P3) 20:20 × 10 cm, (P4) 30 × 10 cm and (P2) 15:15 × 10 cm. The genotype V2 (Girnar 5) performed best in yield and yield contributing characteristics than other genotypes and it was on par with V1 (Girnar 4). Hence, our results concluded that (P4) 25:25 × 10 cm spacing, performing best with (V2) Girnar 5 and (V1) Girnar 4 varieties.

Local climate variability associated to sustainable agriculture at rain shadow areas of mount Rinjani and Tambora in West Nusa Tanggara

Climate is driven by solar energy received on the earth surface and local factor, such as mountains. The solar energy affects climate variables namely, temperature, atmospheric pressure, relative humidity, wind and rain. In addition, mountains perform rain shadow areas and affect variability of local climate. A descriptive research was conducted to study variability of those variables associated to direct normal solar irradiation (DNI), and its possible impact on sustainable agriculture at rain shadow areas of Mt. Rinjani in Lombok and Tambora in Sumbawa, West Nusa Tenggara. The results show that the DNI was relative similar at both sides of the Mt. Rinjani which was 13.15±2.6 MJ m−2day−1 on average. While at Mt. Tambora, the DNI at rain shadow area (southern part) was higher than northern part which were 15.6±2.07 MJ.m−2.day−1 and 13.6±3.2 MJ m−2.day−1 respectively. The DNI was relatively high in low lands and it successively decreased through medium and high lands. ETo, air and soil surface temperature were relatively high at rain shadow areas. In conclusion, the intensity of DNI was not significantly affected by aspect factor of incoming light relative to the Mt Rinjani and Mt. Tambora. The mountains had affected the variability of local climate and performed rain shadow areas to the north from Mt Rinjani and to the south from Mt. Tambora, where there had established typical dry land agriculture of semi arid tropics.

Hybrid Pigeonpea (ICPH 2740) Nodular Activity and Biological Nitrogen Fixation as Influenced by Agronomic Practices

Background: To explore the impact of agronomic practices on nodulation, nitrogenase activity and biological nitrogen fixation in hybrid pigeonpea, a field investigation was under taken at BW5 block ICRISAT development center (IDC), International Crops Research Institute for Semi-Arid Tropics (ICRISAT), Patancheru, Hyderabad, during kharif, 2021 and 2022. Methods: The seedlings were raised in portrays in advance to onset of monsoon during last week of May (28th May in 2021 kharif and 30th May in 2022 kharif) in both the years by filling portrays with cocopeat and vermicompost in 1:1 ratio. Transplanting of 24 days and 25 days old seedlings were done on 20th June in 2021 kharif and 23th June in 2022 kharif, respectively, on the same day of dibbling in the main field at 100 cm × 100 cm ,120 cm × 120 cm square geometry and 150 cm × 60 cm. Nutrient management treatments were imposed one week after sowing. Result: Among the planting methods higher nodule number and nitrogenase activity with transplanting compared to dibbling. 120 cm × 120 cm found higher nodule number plant-1 and nitrogenase activity but biological nitrogen fixation was higher with 100 cm × 100 cm ha-1 basis. With respect on nutrient management practices, control performed well in terms of higher nitrogenase activity and biological nitrogen fixation and on par with integrated approach of 100% soil test based NPK + vermicompost + PSB + seed treatment with Rhizobium. So, with transplanting method of establishment, 100 ´ 100 cm square plant geometry and 100% soil test based NPK + vermicompost + PSB + seed treatment with Rhizobium was recommended agronomic practices for hybrid pigeonpea.

Genetic analysis of tolerance to transient waterlogging stress in pigeonpea (Cajanus cajan L. Millspaugh)

Pigeonpea (Cajanus cajan L. Millspaugh) is mainly grown in the rainfed ecosystem during the monsoon season on deep vertisols, and it often faces transient waterlogging problems due to continuous and heavy downpours during early monsoon seasons. Thus, waterlogging has become a significant issue in most of the pigeonpea growing areas of the semi-arid tropics due to heavy rain during the initial crop growth stage, which causes 30 to 40% economic yield loss in India and around the world. Only a few sources of waterlogging tolerant genotypes are available in pigeonpea but are not in the required duration. Hence, the present investigation was carried out to identify waterlogging tolerant pigeonpea genotypes in different durations suitable for different agroecologies of India and to find ideal selection indices as appropriate strategies to identify waterlogging tolerant genotypes. In this study, 162 genotypes were screened under in vitro conditions for 2, 4, 6, and 8 days by submerging seeds. Of these, 33 genotypes could survive for eight days. Further, following a standard screening protocol; these 33 pigeonpea genotypes were screened under pot culture for two years (2020 and 2021). Based on different morpho-physiological parameters and waterlogging tolerant coefficient, genotypes ICP-10397, ICP-7507, ICP-7869, ICP-7148, ICP-4903 ICP-16309, ICP-7375, ICP-6815, ICP-7507, and ICP-6128 were identified as tolerant to transient waterlogging. In addition, this study reports the existence of substantial genetic variation for waterlogging tolerant traits in pigeonpea. Stress indices, such as stress tolerance index) (STI), mean relative performance (MRP) and relative efficiency index (REI) were identified as the ideal selection index. Therefore, identified genotypes are further validated and can be deployed in waterlogging tolerance pigeonpea breeding programs

Rhizosphere engineering for semiarid tropics: prospects and bottlenecks

Rhizosphere engineering for semiarid tropics: prospects and bottlenecks

Performance of dual-purpose sorghum (Sorghum bicolor) under different sowing windows and crop geometry

India is one of the most vulnerable countries to climate change and its impact on agricultural production and livestock. Sorghum (Sorghum bicolor) is an important food crop of India cultivated in tropical and subtropical climates, especially the semiarid tropics; varying environmental attributes significantly affect its duration and yield. Therefore, the present research aimed to evaluate the potential of dual-purpose sorghum under varying sowing windows and crop geometry. The experiment was conducted in Eastern block farm of Tamil Nadu Agricultural University during the summer season- 2022. The experiment was laid out in strip plot design with three different dates of sowing in the main plot, i.e., D1 - First fortnight of February, D2 - First fortnight of March and D3 - First fortnight of April and six different crop geometries in the subplot viz., 45 x 15 cm (S1),45 x 10 cm(S2), 45 x 5 cm (S3), 30 x 15 cm (S4),30 x 10 cm (S5) and 30 x 5 cm (S6) and replicated thrice.The results revealed that sowing during the first fortnight (I FN) of April with a spacing of 45x 15 cm resulted in maximum grain yield(2585 kg/ha) and for fodder yield, April I FN sowing with a crop geometry of 30x 5 cm resulted in maximum green biomass (43.6 t/ha) as well as dry matter production. So, spacing of 30x 5 cm helps in better utilization of resources along with maximum fodder yield.