Conditions Of Semi-arid Region Research Articles

Combining silicon, organic matter, and Trichoderma harzianum to mitigate salt stress in forage sorghum

Salt stress is a major abiotic factor limiting plant growth worldwide, particularly in arid and semiarid regions where excessive groundwater use in irrigation leads to high salt concentrations. To address this issue, this study investigated the efficacy of silicon, either alone or in combination with Trichoderma harzianum and organic matter, in mitigating salt stress in forage sorghum. The experiment took place in a saline Fluvisol in Parnamirim, a semiarid region of Pernambuco, Brazil, and followed a randomized block design with five treatments and four replicates: sorghum (control); sorghum + Si; sorghum + Si + OM (organic matter); sorghum + Si + T (T. harzianum); and sorghum + Si + T + OM. Sorghum plants were assessed over three cycles (initial cut and two regrowths) from June 2021 to April 2022. The combined treatments of Si + OM, Si + T, and Si + T + OM increased plant growth by 42.17, 35.49, and 27.51%, respectively, compared to the control. Similarly, these treatments led to biomass accumulation gains of 39.42, 40.44, and 31.77% in sorghum plants relative to the control. Silicon alone did not yield significant growth or biomass accumulation improvements. The application of silicon in conjunction with T. harzianum and/or organic matter shows promise in enhancing forage sorghum growth under saline stress conditions in semiarid regions.

Metagenomic and genomic analysis of heavy metal-tolerant and -resistant bacteria in resource islands in a semi-arid zone of the Colombian Caribbean

Bacteria from resource islands can adapt to different extreme conditions in semi-arid regions. We aimed to determine the potential resistance and tolerance to heavy metals from the bacterial community under the canopy of three resource islands in a semi-arid zone of the Colombian Caribbean. Total DNA was extracted from soil and through a metagenomics approach, we identified genes related to heavy metal tolerance and resistance under the influence of drought and humidity conditions, as well as the presence or absence of vegetation. We characterized the genomes of bacterial isolates cultivated in the presence of four heavy metals. The abundances of genes related to heavy metal resistance and tolerance were favored by soil moisture and the presence of vegetation. We observed a high abundance of resistance genes (60.4%) for Cu, Zn, and Ni, while 39.6% represented tolerance. These genes positively correlated with clay and silt content, and negatively correlated with sand content. Resistance and tolerance were associated with detoxification mechanisms involving oxidoreductase enzymes, metalloproteases, and hydrolases, as well as transmembrane proteins involved in metal transport such as efflux pumps and ion transmembrane transporters. The Bacillus velezensis C3-3 and Cytobacillus gottheilii T106 isolates showed resistance to 5 mM of Cd, Co, Mn, and Ni through detoxification genes associated with ABC pumps, metal transport proteins, ion antiporter proteins, and import systems, among others. Overall, these findings highlight the potential of bacteria from resource islands in bioremediation processes of soils contaminated with heavy metals.

Effect of Pashu chocolate supplementation on production and reproductive performance of milch buffalo under field conditions of semi arid region

Pashu chocolate is the brand name of the urea molasses mineral block formulated by KVK, Panchmahal by using of urea, molasses, wheat bran, area specific mineral mixture, black salt, etc. for augment milk production and reproductive performance of dairy animals. A study was conducted to find out the efficacy of Pashu chocolate supplementation on productive and reproductive performance of milking buffalo and feed economics at farmers field in semi-arid zone, during the year 2018 to 2019. Twenty, lactating Mehsana breed of buffalo were randomly selected and distributed equally in to two groups ten each in a completely randomized design i.e., T1 (Control) and T2 (Pashu chocolate supplementations). In the feeding schedule of the present study T1 animals were given 5 to 6 kg dry roughage (sorghum/pearl millet) with green fodder (20 kg Napier-lucerne) added to 2.5 kg concentrate feed/ day, whereas an ad lib lick of UMMB (Pashu chocolate) was offered in the T2 Group in addition to the feeding schedule of T1 Group. An increase of 24.56% in milk i.e., from 6.23±0.40 to 7.76±0.54 L per day was recorded after comparing the outcomes of the two treatments. This significant (P˂0.05) increase in milk production indicates a positive impact of Pashu chocolate on the performance of milch buffaloes. Supplementation of Pashu chocolate as an ad lib lick reduced the postpartum estrus period and service period from 79.7±7.43 and 132.00±13.34 days to 54.3±4.41 and 81.60±7.54 days, respectively. Hence, the findings in the present study indicate beneficial effects of Pashu chocolate on productive and reproductive traits of buffaloes in semi-arid climatic conditions.

Unsaturated transport of Escherichia coli through disturbed soil column: effect of natural zeolite and cow manure addition

Organic and inorganic amendments are routinely applied to ameliorate soil conditions in semi-arid regions. This study aimed to examine the unsaturated transport of nalidixic acid-resistance Escherichia coli (E. coli NAR) in soil amended by cow manure (CM) and natural zeolite (NZ). Two levels of NZ (5 and 15% w/w) were added to a loam soil containing 5% w/w CM and incubated for 60 days. Then, the soil mixtures were poured into cylinders (3.6 × 15 cm) and a pulse (0.1 pore volume) of bacteria suspension (106 Cell mL−1) was added on top of the soil columns and leaching experiments were conducted at a steady-state, unsaturated flow condition and filtration coefficient (λf ), relative adsorption index (SR ), maximum depth of bacteria transport (Zmax ), average (Cav ) and cumulative cell density (Ccum ) were calculated. CM and NZ application significantly increased the peak density, Z max , C av , and C cum of E. coli NAR. The Cav , and Ccum of E. coli NAR in both 5 and 15% NZ containing mixtures were about 1 and 2-fold higher compared to the control. CM and NZ addition to soil decreased the filtration coefficient (λf ) and relative adsorption index (SR ) compared to the control. According to our results, we should conclude that the presence of NZ and CM, separately or together, can significantly increase the risk of groundwater contamination and it should be used with prudence.

Response of Wheat Crop to Potassium Fertilization Under Rain-fed Conditions in Semi-arid Regions

Wheat is regarded as one of the major field crops that is mainly grown under rain-fed conditions in Jordan. However, wheat productivity is relatively lower than the world average. This is primarily due to the prevailing drought conditions as a result of poor distribution and low amounts of rainfall. Research studies showed that K can markedly improve wheat yield and quality under water deficit conditions. The objective of the current study was to investigate the effect of soil-applied mineral potassium (K) fertilizer on the yield and growth parameters of two local durum wheat varieties under rain-fed conditions in Jordan. And to determine the rate of K needed to obtain the optimum wheat yield. Two field trials were conducted under rain-fed conditions in two locations in Jordan. Two local durum wheat varieties were grown during two successive growing seasons. Five different rates of K were applied at sowing time. A randomized complete block design with four replications was followed. The results showed that soil K application exhibited a significant effect on wheat crop grain and biological yields of both varieties at the two locations. However, an increasing trend in plant height, harvest index, and thousand-grain weight with increasing K application rate was noticed. Potassium application to soil can alleviate the adverse effects of drought stress on the wheat crop by improving growth and yield attributes.

Nutrients in ‘Gigante’ forage cactus pear under different saline water irrigation depths and planting densities

ABSTRACT Climate variability tends to increase the occurrence of extreme drought conditions in semi-arid regions, thereby compromising crop yield, including that of drought-tolerant plants such as forage cactus pear. Irrigation of cactus with saline water has enabled good results, and its combination with changes in planting densities may promote changes in the production response of this crop. A field experiment spanning two crop cycles was carried out to evaluate nutrient concentrations in ‘Gigante’ forage cactus pear (Opuntia ficus-indica Mill) under different saline water irrigation depths and planting densities. A randomized block design was used with treatments arranged in split-split plots. Two irrigation intervals (7 and 14 days) were assigned to plots, four planting densities (20,000; 40,000; 60,000 and 80,000 plants ha-1) to subplots, and four irrigation depths of saline water of electrical conductivity 2.91 dS m-1 (0, 11, 22 and 33% of reference evapotranspiration) to sub-subplots. The irrigation depths were applied only in the period of the year without rain. Intermediate planting densities (43,002 and 54,687 plants ha-1) promote lower P, Ca and Fe concentrations in cladode tissues of forage cactus pear. Irrigating ‘Gigante’ cactus forage with saline water up to 33% ETo increases the concentrations of N, P, Ca, Mg, B, Cu, Mn and Zn in cladode tissues. Irrigation levels between 16 and 25% of ETo with saline water resulted in the highest concentrations of K, S and Na.

Effect of tillage and weed control measures on the yield and economic efficiency of maize under rainfed conditions of semi-arid region

Effect of tillage and weed control measures on the yield and economic efficiency of maize under rainfed conditions of semi-arid region

Adaptability to local conditions and phylogenetic differentiation of microsymbionts of TGx soybean genotypes in the semi-arid environments of Ghana and South Africa

The study of the nitrogen fixation and phylogenetic diversity of nodule microsymbionts of grain legumes in many parts of the globe is often carried out in order to identify legume-rhizobia combinations for agricultural sustainability. Several reports have therefore found that rhizobial species diversity is shaped by edapho-climatic conditions that characterize different geographic locations, suggesting that rhizobial communities often possess traits that aid their adaptation to their habitat. In this study, the soybean-nodulating rhizobia from semi-arid savannahs of Ghana and South Africa were evaluated. The authenticated rhizobial isolates were highly diverse based on their colony characteristics, as well as their BOX-PCR profiles and gene sequences. In the 16S rRNA phylogeny, the isolates were placed in the different clades Bradyrhizobium iriomotense and Bradyrhizobium jicamae together with two superclades Bradyrhizobium japonicum and Bradyrhizobium elkanii. The multilocus (atpD, glnII, gyrB, recA) phylogenetic analyses indicated the dominance of Bradyrhizobium diazoefficiens and putative new Bradyrhizobium species in the semi-arid Ghanaian region. The phylogenetic analyses based on the symbiotic genes (nifH and nodC) clustered the test isolates into different symbiovars (sv. glycinearum, sv. retame and sv. sojae). Principal component analysis (PCA) showed that soil factors played a significant role in favoring the occurrence of soybean-nodulating microsymbionts in the tested local conditions. The results suggested that isolates had marked local adaptation to the prevailing conditions in semi-arid regions but further studies are needed to confirm new Bradyrhizobium species.

Growth and vase life of gladiolus plants cultivated under different conditions in the semi-arid region of Brazil

Abstract Cultivation conditions are determining factors that affect the quality of cut flowers. The objective of this study was to evaluate the vegetative growth, flowering and vase life of commercial gladiolus cultivars under different shading conditions in the Brazilian semi-arid region. Two cultivars of gladiolus (Jester and Rose Friendship) were grown under two conditions: full sun and 70% shade. Biometrics were evaluated 60 days after planting and the growth rate of the crop was evaluated at 15-30, 30-45 and 45-60 days for the variables: number of tillers, stem diameter, number of leaves and plant height. After 45 days, the fresh weight, dry weight and total relative water content of the area and root parts of the plants were evaluated. After the harvest, the stems were kept at a temperature of 22±3 °C and relative humidity (RH) of 60%. Visual assessment, pH of the solution, variation in the volume of water and loss of fresh mass were measured every two days. Cultivation with 70% shading resulted in greater accumulation of biomass in the aerial part of gladiolus plants, greater neck diameter and height. The Rose Friendship cultivar underwent a greater translocation of dry matter to the aerial part of the plants, resulting in greater height. On the other hand, the gladiolus stems from cultivation under full sun conditions resulted in longer vase life, 10 days under conservation conditions at 22±3 °C and RH 60%.

English

Crop yields are declined due to low soil fertility, insufficient soil water availability and poorly managed cropping systems in Limpopo province of South Africa. Phosphorus (P) is a major essential nutrient element required by crops for enhanced growth and development. Interactions between different rates of P fertilization and strip intercropping system have not been studied in detail under rainfed conditions in semi-arid region of Limpopo province. Therefore, this study was conducted to assess the performance of four cowpea varieties at four levels (0, 15, 30, 45 kg P ha-1) of P fertilization in a cowpea-maize intercropping system in a split-split plot design during two seasons. Significant interactions were obtained between variety and phosphorus application as well as variety and cropping system for 90% physiological maturity, root mass and grain yield in both seasons. P levels significantly influenced and enhanced grain yield, land equivalent ratio, profit and benefit cost ratio achieved. PAN311 and TVu13464 matured earlier across P levels and they were selected promising cowpea varieties based on their early maturity and high yield. Land equivalent ratio values were greater than 1.0, which indicated performance and advantage of an intercropping system over monocropping system in land utilisation. The optimum P level for cowpea-maize strip intercropping was at 30 kg P ha-1 based on yield and financial return. The results showed that P application enhanced the productivity of the cowpea varieties in cowpea-maize strip intercropping in the semi-arid environment of Limpopo province. © 2021 Friends Science Publishers

Impact of Biological Fertilizer Arbuscular Mycorrhizal Fungi and Conventional Fertilizers Mobilization on Growth, Yield, Nutrients Uptake, Quercetin and Allin Contents in Allium Crops Cultivation Under Field Conditions in Semi-Arid Region of India

Field experiment was conducted at farmer field Lasalgaon in the state of Maharashtra, India to determine the influence of arbuscular mycorrhizal fungi (AMF) to reduce the doses of chemical fertilizer used in major allium crops (red onion, white onion and garlic) during winter cultivation. AMF inoc-ulated and uninoculated onion and garlic seedlings/cloves were grown with recommended dose of fertilizer (100% RDF) and Mycorrhiza +75% RDF. AMF inoculated onion and garlic plant showed significant increase in plant growth parameters like plant height, total biomass, neck thickness, bulb diameters and bulb weight. AMF + 75% RDF treatments resulted into greater plant morphological characters, highest yield, height, TSS, quercetin and allin contents and AMF root colonization as compared to uninoculated control (100% RDF). The results reveal that AMF contribute to growth and development of onion and garlic plant under field conditions. In the present study, it can be concluded that AMF could reduce the amount of chemical fertilizers to enhancing overall performance of onion and garlic and provide a sustainable and environmentally safer option for cultivation.

Melatonin improves the seed filling rate and endogenous hormonal mechanism in grains of summer maize.

The unpredictable precipitation and water deficit conditions in semiarid regions significantly reduce the yield of summer maize. The exogenous application of plant growth regulators can be used as a strategy to enhance plant stress tolerance and improve the growth and yield of maize under semiarid conditions. Here, we studied the protective role of melatonin application on maize yield using grain filling rate and hormonal crosstalk in maize grains. In the first field experiment, seeds were soaked with melatonin at a concentration of 0 (SM0 ), 25 (SM1 ), 50 (SM2 ), and 75 μM (SM3 ) μM. In contrast, in the second experiment, melatonin was applied on the foliage at the ninth leaf stage at a concentration of 0 (FM0 ), 25 (FM1 ), 50 (FM2 ), and 75 (FM3 ) μM. Our findings showed that melatonin treatments as seed soaking significantly increased single seed weight, seed filling rate in superior, medium and inferior seeds by regulating the hormone levels compared to foliar application. Application of melatonin significantly increased the zeatin+zeatin riboside (Z+ZR), indole-3-acetic acid (IAA), and gibberellic acid (GA) contents. However, it significantly inhibited the contents of abscisic acid (ABA) during the seed filling period. The content of Z+ZR, IAA, and GA was positively correlated with the maximum seed filling rate, seed weight, and mean filling rate in middle, superior and lower seeds, while the ABA was negatively correlated. The ABA content in inferior seeds was positively correlated with the maximum and mean seed filling rate. In semiarid regions, melatonin treatment of SM2 and FM2 significantly increased the dry matter per plant, 100-grain weight, seed filling rate, IAA, Z+ZR, GA contents, ear characteristics, and maize yield.

Evaluation of Sweet Sorghum Bagasse as an Alternative Feed Resource for Livestock in Semi Arid Regions

Production of good quality fodder is of a great importance for the economical livestock. The objective of this proposal is to evaluate the potential of sweet sorghum bagasse as an alternative feed resource for livestock. The research was conducted at Akcakale/Sanlıurfa from June to November in 2016 and 2017 according to randomized complete block design with four replications. Harvest was performed between milk and soft dough stages. After the leaves and panicle of the plant were stripped, sap-extracted plants (bagasse) were ensiled and silage quality attributes were also determined. There were statistically significant differences in sweet sorghum genotypes in terms of bagasse yield and all examined feed quality characteristics. Depending on two-year averages; bagasse yield, dry matter (DM) yield, crude protein (CP) ratio, acid detergent ligin (ADL), neutral and detergent fiber (NDF), and acid detergent fiber (ADF) were ranged from 51.9-86.7 t ha-1, 12.1-21.7 t ha-1, 35.39-45.61 g kg DM, 40.58-78.88 g kg DM, 473.0-653.0 g kg DM, and 273.3-431.6 respectively.It is concluded that the silages of sweet sorghum bagasse which were grown the 2nd production conditions in semiarid region can be considered as roughage.

Delineating multivariate divergence, heritability, trait association and identification of superior omega-3-fatty acid specific genotypes in linseed (Linum usitatissimum L.)

Present investigation was undertaken to evaluate 50 linseed genotypes for three consecutive years for seed yield, oil content and agro-morphological traits using multivariate approach. Higher range, large value of Shannon-weaver diversity index for both traits and genotypes and large differences in mean values for most of the characters showed that a wide and significant variation existed among the genotypes and traits. Pooled analysis of variance revealed highly significant differences (p<0.001) among the genotypes for all the characters studied. The magnitude of the phenotypic coefficient of variation was somewhat higher than the genotypic coefficient of variation, indicating that the environment had little impact on the expression of these traits. Cluster analysis for yield and agro-morphological traits using unweighted pair group method of arithmetic averages (UPGMA) grouped the genotypes into nine clusters with varied number. Clustering of linseed genotypes from different geographical locations or source/origin into same cluster has confirmed that they are genetically related, and possibly from the same progenitor. The principal component analysis (PCA) revealed that most of the variation (76.41%) was accounted by first four PCA and indicated role of traits that contributed significantly towards a wide variation among the genotypes. The positive associations of seed yield per plant and oil content with component trait implies that improving one or more component traits could result in genetic enhancement of seed yield and oil content in linseed. The significant negative association of seed yield per plant and oil content with days to flowering and days to maturity has great advantages in breeding short duration linseed cultivars for hot and water stress climatic conditions of semi-arid regions. Trait specific genotypes namely, Shival, Sharda, IC54970, Mukta, IC56363, T-397, IC53281 and RLC-92 were identified for the development of short duration and dwarf cultivars with higher omega-3-fatty acid content.

Economics of producing quality seedlings of important agroforestry species with different growing media under shade-net conditions in semi-arid region of Rajasthan

A field experiment was conducted during June, 2019 to March, 2020 at the Instructional farm Fruit Science at the College of Horticulture and Forestry, Jhalawar, Agriculture University Kota (Rajasthan). The experiment was comprised of eighteen treatments of four growing medium viz.; soil, sand, FYM and Vermicompost in different ratio. The study aimed to find out best growing medium for following three species viz. Ardu (Ailanthus excelsa), Bael (Aegle marmelos) and Neem (Azadirachta indica). Seedlings were raised in the polybags of size 6” x 10” under green shed net (50% light intensity) nursery conditions. Highest Benefit cost ratio of 2.23, 2.97 and 2.23 was observed in T0 with lowest cost of cultivation as used only soil as growing medium for Ardu, Bael and Neem respectively whereas revenue remained constant for Bael Rs.20 per seedling and for Ardu and Neem Rs. 15 only in all the treatments. The results obtained from this study can be used to produce quality planting material of Ardu, Bael and Neem in shortest possible time and lowest quality input.

Sesame Seed Yield and Growth Traits Response to Different Row Spacing in Semi-Arid Regions

Plant density is one of the most important factors influencing the physiological, morphological characteristics, and yield of sesame. Sesame is an important oilseed and cash crop production in Sudan. The effects of different rows spacing on the growth attributes, yield and yield compound on three sesame seeds varieties were investigated at rainfall conditions in semi-arid regions. Two field experiments were conducted in 2014-2015 and 2015-2016. Three varieties were planted at four rows spacing [5(control), 10, 20 and 30cm]. The experiment was laid out in RCBD in split plots with three replications. There were significant differences between row spacing, varieties and interaction between row spacing and varieties for all parameters except the 1000 seeds weight. Moreover, Abo Nama has recorded the highest plants, number of branches and number of capsules per plant, while the abo Radom recorded the highest number of seeds per capsule and seed yield, and abo sofa had the highest weight of 1000 seeds. Planted varieties at the 5 cm between rows can increase the seed yield (210.18 kg/h). The interaction between Abo Radom and control recorded the high seed yield by 265.30 kg per h-1. This study suggests that the appropriate rows spacing can actively increase the yield of the sesame plant.

An Overview of Managed Aquifer Recharge in Brazil

In order to face the severe climate conditions in semiarid regions, many managed aquifer recharge (MAR) and rainwater storage systems have been implemented by local communities. Governmental programs have helped to propagate the concept of MAR. Based on a systematic review, popular initiatives, current legislation, and research lines and programs were compiled and analyzed. Although the MAR global inventory points to the prevalence of in-channel modifications among ninety MAR sites, the Barraginhas Project alone has been responsible for the construction of more than 500,000 infiltration ponds up to 2013. In urban areas, aquifer recharge initiatives mostly aim to reduce runoff peak flows. In some cases these initiatives have been stimulated by urban drainage public policies. Compared to countries such as the USA and Australia, Brazil is still at an early stage in MAR initiatives and needs to overcome technical, legal, and socio-cultural challenges to adopt MAR approaches, in order to help in facing water security challenges in a future climate change scenario. This article aims to provide an overview of the state of the art concerning technological, scientific, and legal issues around MAR in Brazil and the respective challenges for the adoption of this approach at a national level.

Water Balance and Soil Moisture Deficit of Different Vegetation Units under Semiarid Conditions in the Andes of Southern Ecuador

Water availability in semiarid regions is endangered, which is not only due to changing climate conditions, but also to anthropogenic land use changes. The present study analyzed the annual and monthly water balance (WBc) and the soil moisture deficit (Ds) for different vegetation units under semiarid conditions in the Andes of southern Ecuador, based on limited meteorological station data and field measurements (soil samples). To calculate crop evapotranspiration (ETc) the Blaney–Criddle method was applied, and the specific crop factor (Kc) included, because only temperature (T) and precipitation (P) data were available. By means of the soil samples the water retention capacity (RC) of the different soil types present in the study area were estimated, which, in combination with WBc, provided reliable results respective to water surpluses or deficits for the different vegetation units. The results indicated highest Ds for cultivated areas, particularly for corn and sugarcane plantations, where annual deficits up to −1377.5 mm ha−1 and monthly deficits up to −181.1 mm ha−1 were calculated. Natural vegetation cover (scrubland, forest and paramo), especially at higher elevations, did not show any deficit throughout the year (annual surpluses up to 1279.6 mm ha−1; monthly surpluses up to 280.1 mm ha−1). Hence, it could be concluded that the prevailing climate conditions in semiarid regions cannot provide the necessary water for agricultural practices, for which reason irrigation is required. The necessary water can be supplied by areas coved by natural vegetation, but these areas are endangered due to population growth and the associated land use changes.

Short-Term Effects of Tillage Intensity and Fertilization on Sunflower Yield, Achene Quality, and Soil Physicochemical Properties under Semi-Arid Conditions

Inappropriate soil management practices and specific climatic conditions in semi-arid region cause loss of soil organic matter (SOM), decline soil fertility, and trigger soil erosion processes and desertification. A two-year field study was carried out to investigate the effects of tillage intensity and fertilizer regime treatments on the productivity of sunflower (Helianthus annus L.) and soil physicochemical properties in the semi-arid highland region in northwest Iran (37°31′ north (N), 46°53′ east (E)). Five fertilizer treatments were included under conventional (CT) or reduced tillage systems (RT): F1, no fertilizer application; F2, 20 t∙ha−1 farmyard manure (FYM); F3, 40 t∙ha−1 FYM; F4: 20 t∙ha−1 FYM + 50% of the recommended dose of nitrogen–phosphorus–potassium (NPK) chemical fertilizer; F5: full dose of the recommended chemical NPK fertilizer. Results showed that utilization of FYM decreased bulk density (BD); its effects were more evident under the highest SOM content for the F2 and F3 treatments, whereas application of mineral fertilizer had no significant effect upon SOM content, and elevated levels of FYM preserved higher organic carbon contents in topsoil. The highest N, P, and K contents of the soil were obtained with FYM plus inorganic fertilizer application in the RT system. Hydraulic conductivity and soil moisture content were significantly improved by RT and FYM application. The highest root growth was observed for F3 and F4 under the RT system. The effect of fertilizer and tillage treatments was more pronounced during the second year. Traits related to growth and seed quality such as achene oil content, leaf area, and harvest index were enhanced by chemical fertilization in the CT system. The highest achene yield and oil percentage were recorded for plants grown with F3 and F4. The best option for enhancing sunflower productivity and quality in semi-arid, high-altitude environments is the application of organic fertilizers amended with reduced amounts of chemical fertilizers.

Environmental correlates of seed weight of tropical semi-arid woody species

The survival and distribution of plant species in the extreme environmental conditions of semi-arid regions is strongly dependent on traits associated with drought resistance. Seed weight may be particularly important, since larger seeds are predicted to promote survival in harsh environments, especially those of low soil moisture. Here, we test this hypothesis using data on the seed weight of 277 woody plant species in the semi-arid Caatinga biome of northeast Brazil. We used Structural Equation Models (SEM) to test for associations between seed weight and biophysical conditions, including temperature, precipitation, climatic seasonality, soil-vegetation interaction and soil compaction. Species occurrence data were geographically biased due to large areas of the biome that remain under-collected. The strongest statistical association was between seed weight and soil compaction, with mean temperature of the driest quarter and aridity directly influencing soil compaction (and indirectly influencing seed weight). We conclude that the larger seeds of woody species in the Caatinga are primarily an adaptation to compacted soil, uneven distribution of rainfall and high temperatures, intrinsic conditions of the Caatinga biome.