Nitrogen-deficient Soils Research Articles

Influence of indole acetic acid and trehalose, with and without zinc oxide nanoparticles coated urea on tomato growth in nitrogen deficient soils

Nitrogen deficiency in low organic matter soils significantly reduces crop yield and plant health. The effects of foliar applications of indole acetic acid (IAA), trehalose (TA), and nanoparticles-coated urea (NPCU) on the growth and physiological attributes of tomatoes in nitrogen-deficient soil are not well documented in the literature. This study aims to explore the influence of IAA, TA, and NPCU on tomato plants in nitrogen-deficient soil. Treatments included control, 2mM IAA, 0.1% TA, and 2mM IAA + 0.1% TA, applied with and without NPCU. Results showed that 2mM IAA + 0.1% TA with NPCU significantly improved shoot length (~ 30%), root length (~ 63%), plant fresh (~ 48%) and dry weight (~ 48%), number of leaves (~ 38%), and leaf area (~ 58%) compared to control (NPCU only). Additionally, significant improvements in chlorophyll content, total protein, and total soluble sugar, along with a decrease in antioxidant activity (POD, SOD, CAT, and APX), validated the effectiveness of 2mM IAA + 0.1% TA with NPCU. The combined application of 2mM IAA + 0.1% TA with NPCU can be recommended as an effective strategy to enhance tomato growth and yield in nitrogen-deficient soils. This approach can be integrated into current agricultural practices to improve crop resilience and productivity, especially in regions with poor soil fertility. To confirm the efficacy of 2mM IAA + 0.1% TA with NPCU in various crops and climatic conditions, additional field studies are required.

Quantifying chlorophyll content index for efficient nitrogen management in rice (Oryza sativa L.)

Applying nitrogen fertilizer strategically enhances rice productivity in nitrogen-deficient soils. Splitting fertilizer doses across growth stages optimizes nutrient use efficiency. Monitoring chlorophyll levels correlates closely with leaf nitrogen content, crucial for assessing crop health. Non-destructive chlorophyll content meter techniques, such as the Chlorophyll Content Index (CCI), allow for precise nitrogen management adjustments in the field. However, its critical value may differ depending on crops and varieties. Hence, to find out the critical CCI value for rice cv. ADT 43, observational trials were conducted at the Experimental Farm of Annamalai University during two seasons Kuruvai (June-Oct 2023) and Navarai (Dec-March 2024). The pooled data of the present study indicated that the average LNC (maximum tillering, panicle initiation and booting stages) has a linear relationship (R2=0.8545) with the yield of rice crop. The corresponding higher yield ( greater than 7t/ha) coincided with LNC of 3.1%. Likewise, the average CCI has a linear relationship (R2=0.9031) with the LNC of rice plants. The corresponding LNC ( greater than 7t/ha) was matched with the CCI value of 29. This CCI value of 29 is considered as the critical CCI value. CCI can be used as a decision-support tool for N-fertilization of short duration rice crop, and when CCI reduced below this critical value the farmers can fertilise the field with adequate N.

Molecular Diversity and Combining Ability in Newly Developed Maize Inbred Lines under Low-Nitrogen Conditions.

Nitrogen is an essential element for maize growth, but excessive application can lead to various environmental and ecological issues, including water pollution, air pollution, greenhouse gas emissions, and biodiversity loss. Hence, developing maize hybrids resilient to low-N conditions is vital for sustainable agriculture, particularly in nitrogen-deficient soils. Combining ability and genetic relationships among parental lines is crucial for breeding superior hybrids under diverse nitrogen levels. This study aimed to assess the genetic diversity of maize inbred lines using simple sequence repeat (SSR) markers and evaluate their combining ability to identify superior hybrids under low-N and recommended conditions. Local and exotic inbred lines were genotyped using SSR markers, revealing substantial genetic variation with high gene diversity (He = 0.60), moderate polymorphism information content (PIC = 0.54), and an average of 3.64 alleles per locus. Twenty-one F1 hybrids were generated through a diallel mating design using these diverse lines. These hybrids and a high yielding commercial check (SC-131) were field-tested under low-N and recommended N conditions. Significant variations (p < 0.01) were observed among nitrogen levels, hybrids, and their interaction for all recorded traits. Additive genetic variances predominated over non-additive genetic variances for grain yield and most traits. Inbred IL3 emerged as an effective combiner for developing early maturing genotypes with lower ear placement. Additionally, inbreds IL1, IL2, and IL3 showed promise as superior combiners for enhancing grain yield and related traits under both low-N and recommended conditions. Notably, hybrids IL1×IL4, IL2×IL5, IL2×IL6, and IL5×IL7 exhibited specific combining abilities for increasing grain yield and associated traits under low-N stress conditions. Furthermore, strong positive associations were identified between grain yield and specific traits like plant height, ear length, number of rows per ear, and number of kernels per row. Due to their straightforward measurability, these relationships underscore the potential of using these traits as proxies for indirect selection in early breeding generations, particularly under low-N stress. This research contributes to breeding nitrogen-efficient maize hybrids and advances our understanding of the genetic foundations for tolerance to nitrogen limitations.

OsCIPK2 mediated rice root microorganisms and metabolites to improve plant nitrogen uptake

Crop roots are colonized by large numbers of microorganisms, collectively known as the root-microbiome, which modulate plant growth, development and contribute to elemental nutrient uptake. In conditions of nitrogen limitation, the over-expressed Calcineurin B-like interacting protein kinase 2 (OsCIPK2) gene with root-specific promoter (RC) has been shown to enhance growth and nitrogen uptake in rice. Analysis of root-associated bacteria through high-throughput sequencing revealed that OsCIPK2 has a significant impact on the diversity of the root microbial community under low nitrogen stress. The quantification of nifH gene expression demonstrated a significant enhancement in nitrogen-fixing capabilities in the roots of RC transgenetic rice. Synthetic microbial communities (SynCom) consisting of six nitrogen-fixing bacterial strains were observed to be enriched in the roots of RC, leading to a substantial improvement in rice growth and nitrogen uptake in nitrogen-deficient soils. Forty and twenty-three metabolites exhibiting differential abundance were identified in the roots and rhizosphere soils of RC transgenic rice compared to wild-type (WT) rice. These findings suggest that OSCIPK2 plays a role in restructuring the microbial community in the roots through the regulation of metabolite synthesis and secretion. Further experiments involving the exogenous addition of citric acid revealed that an optimal concentration of this compound facilitated the growth of nitrogen-fixing bacteria and substantially augmented their population in the soil, highlighting the importance of citric acid in promoting nitrogen fixation under conditions of low nitrogen availability. These findings suggest that OsCIPK2 plays a role in enhancing nitrogen uptake by rice plants from the soil by influencing the assembly of root microbial communities, thereby offering valuable insights for enhancing nitrogen utilization in rice cultivation.

The Importance of Lentils: An Overview

The legume family includes approximately 19,300 species across three large subfamilies, of which Papilionoideae stands out with 13,800 species. Lentils were one of the first crops to be domesticated by humans, approximately 11,000 BP. They are diploid legumes that belong to the Papilionoidea subfamily and are of agricultural importance because of their resistance to drought and the fact that they grow in soil with a pH range of 5.5–9; therefore, they are cultivated in various types of soil, and so they have an important role in sustainable food and feed systems in many countries. In addition to their agricultural importance, lentils are a rich source of protein, carbohydrates, fiber, vitamins, and minerals. They are key to human nutrition since they are an alternative to animal proteins, decreasing meat consumption. Another characteristic of legumes, including lentils, is their ability to form nodules, which gives them a growth advantage in nitrogen-deficient soils because they enable the plant to fix atmospheric nitrogen, thus contributing nitrogen to the soil and facilitating the nutrition of other plants during intercropping. Lentils have also been applied for protection against various human diseases, as well as for phytoremediation, and they also have been applied as environmental bioindicators to identify cytotoxicity. This review addresses the importance of lentils in agriculture and human health.

Potential of a novel endophytic diazotrophic Serratia sp. Wed4 for pyrene biodegradation

Endophytic diazotrophic Serratia sp. Wed4 with high nitrogenase activity (1260.9 ± 8.3 nmol C2H4 mL−1h−1) was isolated from Glycine max Linn growing in PAH contaminated soil for improving PAH removal and crop growth. Strain Wed4 biodegraded 37.0% of pyrene within 14 d via phthalate pathway in vitro and could biodegraded other PAHs with 2–5 rings effectively. Its capabilities on promoting crop growth included indole acetic acid (IAA) production (30.8 ± 3.3 μg mL−1), iron carrier production (A/Ar = 0.841 ± 0.002), inorganic phosphate dissolution (D/d = 1.184 ± 0.032) and organic phosphate dissolution (D/d = 1.154 ± 0.025). Strain Wed4 successfully colonized in barley tissues (>104 CFU g−1 FW), significantly promoted barley growth and nitrogen nutrition, reduced pyrene residues especially in shoots. Under sufficient nitrogen condition, strain Wed4 significantly promoted the dry weight of barley by 18.9%–33.9%, and decreased the pyrene residues by 46.4% in shoots and by 32.1% in roots. Meanwhile, under the deficient nitrogen condition, strain Wed4 significantly promoted the dry weight of barley by 40.1%–63.3% and decreased the pyrene residues by 39.0% in shoots and by 28.0% in roots. The pyrene contents were significantly negatively correlated with the total nitrogen contents in barley tissues, suggesting that nitrogen fixation of strain Wed4 also stimulated the pyrene removal. Based on its performance, Serratia sp. Wed4 provided a great potential to increasing crop yield and reducing PAH pollution in nitrogen deficient soils.

Diversity, Ecology and Phytogeography of Bryophytes across Temperate Forest Communities-Insight from Mt. Papuk (Croatia, SE Europe).

It has been widely documented that the complex structure of forest ecosystems supports considerable bryophyte species and functional diversity. In this study, we assessed the diversity, distribution and ecological and phytogeographical features of bryophytes across a gradient of temperate forest types on Mt. Papuk. This is the largest and highest mountain in the lowland, Pannonian part of Croatia, with high geological diversity and various temperate forests covering 95% of the mountain. According to the predominant tree species (oak vs. beech), geological bedrock (calcareous vs. siliceous) and soil reaction (alkaline vs. acidic), 21 study plots were classified into four distinct forest types. In all, 184 bryophyte species (35 liverworts and 149 mosses) were recorded. Although the forest types investigated did not differ significantly with respect to species richness, each was characterized by a considerable number of diagnostic bryophyte species. According to our results, one of the main ecological factors determining the variability of the forest bryophyte composition was geological bedrock and the associated soil reaction. Basiphilous forests developed on carbonate bedrock harbored more thermophilous and nitrophilous bryophytes and were characterized by southern-temperate and Mediterranean-Atlantic biogeographic elements. In contrast, acidophilous forests growing on silicate bedrock were characterized by wide-boreal and boreo-arctic-montane elements, i.e., bryophytes indicating cooler habitats and nitrogen-deficient soils. Based on the results, we hypothesized that the main latitudinal biogeographic distinction between southern and northern biogeographic elements is driven more by geological substrate than by the main tree species in forest communities. The present study confirmed previous findings that bryophytes are good and specific habitat indicators and show associations with different forest types, which can help to understand the complexity, ecological microconditions and biogeographic characteristics of forest communities.

DIVERSITY OF PITCHER PLANTS (NEPENTHES SPP.) IN RIAU ARCHIPELAGO PROVINCE, INDONESIA

Nepenthes spp. is a unique carnivorous plant with the modified leaf lamina as a pitcher to trap insects. Nepenthes usually produce lower traps near the base of the plant, and upper pitchers form a loop in the tendril, allowing it to wrap around the nearby plant. Pitcher plants, being insectivorous plants, can grow in nitrogen-deficient soils. In the Riau Archipelago Province, the intense land conversion to establish ecotourism in national parks disturbed the pitcher plant habitat, even though the pitcher plants have great potential as ornamental plants. Therefore, for in situ conservation, the existing endemic flora may benefit tourist attractions to support local ecotourism efforts. Based on the above discussion, the presented study aimed to characterize the pitcher plants’ diversity and analyze the relationship among its species using morphological markers in the islands of Bintan, Karimun, and Lingga, Indonesia. Based on the collection and identified pitcher plants, the study discovered that the genus Nepenthes comprises 25 accessions belonging to six different species, i.e., N. gracilis, N. × trichocarpa, N. reinwardtiana, N. ampullaria, N. rafflesiana, and N. × hookeriana. The cluster analysis grouped two main clusters that have a similarity coefficient of 31%–97% based on morphological characteristics among Bintan, Karimun, and Lingga accessions. However, the cluster constructions were more on the traits’ similarity than locality based. For principal component analysis (PCA), 19 morphological traits can benefit as diagnostic features to distinguish the pitcher groups. The study revealed that pitcher plants have diverse phenotypic plasticity in the Riau Archipelago, which is experiencing land conversion for tourism activities. The pitcher plants diversity has the genetic potential for ornamental plants development and is a biological wealth that requires conservation for research, tourism activities, and future generations.

A new bacterial endosymbiotic relationship in Kluyveromyces marxianus isolated from the mezcal fermentation process

In Mexico, agave has a significant cultural and economic impact via its use as a raw material for producing fermented drinks. The agave plant grows in arid and nitrogen-deficient soil where it associates with fungi and bacteria to meet nutrient demands, particularly under extreme conditions of fungal growth; this community of microorganisms is called the microbiome. In the microbiome, aromatic volatile synthesis activates the defense response, resistance to abiotic stress, and plant growth. These aromatic volatiles also impact the organoleptic characteristics of fermented beverages and are produced by microorganisms during agave fermentation. This research presents the behavior of K. marxianus cultivated in the presence of extreme and deficient nitrogen concentrations. In addition, a new biological relationship between K. marxianus ITD0090 from mezcal fermentation and Bacillus tequilensis ITD-UANL-01 is reported, confirmed by fluorescence microscopy and intracellular recovery. Our results also reveal that B. tequilensis ITD-UANL-01 is a nitrogen-fixing bacterium that provides assimilable nitrogen to K. marxianus under nitrogen starvation conditions. This phenomenon allows for 144 h of viability without nitrogen. Furthermore, this is the first report of an endosymbiont of K. marxianus ITD0090 in fermentation.

Microbial Community Investigation of Wild Brambles with Root Nodulation from a Calcareous Nitrogen-Deficient Soil

This study examines culturable diazotrophs and non-culturable bacteria found in the rhizospheres and root pseudonodules of wild blackberry plants (Rubus ulmifolius) that dwell on an unmanaged calcareous nitrogen-deficient soil. The DNA was extracted from the nodules and rhizospheres, and 16S rRNA gene metabarcoding was carried out. The metagenome functions were predicted with bioinformatic approaches. The soil samples were analyzed for the physico-chemical properties. The culturable diazotrophs were isolated and evaluated for the biochemical and plant growth-promoting properties. The soil was classified as nutrient-depleted calcareous soil. The microbial communities of the nodules and rhizospheres showed marked differences. The Pseudomonadota was the nodules’ dominant phyla (90%), while the Actinobacteriota was the most abundant (63%) in the rhizospheres. Stenotrophomonas was the dominant genus (55%) in the nodules, while the Streptomyces genus was widely present (39%) in the rhizospheres. The differences among the nodule and rhizosphere microbial communities were also highlighted by the metagenome function predictions. The gene copies (KOs) revealed the most interesting findings. Similar KOs involved in the nitrogen fixation were found to be similar in terms of the nodules and rhizospheres. However, the nitrate reduction was higher in the rhizosphere, while the denitrification was more prominent in the nodules. Nine diazotrophs were isolated from the nodules and rhizospheres. The plant growth promoting traits’ characterization has shown the interesting potential of the isolates in improving the acquisition of nutrients in plants, promoting their growth, and tolerating stress. Based on interesting biochemical and plant growth-promoting traits, the isolate N2A was further characterized and identified as Pantoea agglomerans.

Reduction of methoxypyrazines with ‘vegetable-like’ odors in grapes by foliar nitrogen application

The influences of foliar nitrogen fertilizers on methoxypyrazines and the correlation between methoxypyrazines and amino acids in Cabernet Sauvignon were studied in nitrogen-deficient soil. Foliar urea and phenylalanine fertilizers (U and P, respectively), and CK were applied three times during veraison. Field trials in 2018 and 2019 revealed that nitrogen fertilizers could effectively increase leucine, valine and isoleucine in grapes and P was more effective than U in 2018. P significantly decreased methoxypyrazines in grapes and wines, thanks to effectively lower expression of VvOMT1, VvOMT2, VvOMT3 and VvOMT4 than other treatments, while U resulted in the highest content of methoxypyrazines among all treatments, due to the higher genes expression. A correlation analysis found that there was little correlation between the methoxypyrazines composition and their amino acid precursors in grapes. Our findings reveal that foliar phenylalanine fertilizer had the highest potential to weaken vegetable-like odors in wines from a nitrogen-deficient vineyard.

​Diversity of Non-heterocystous Cyanobacteria in Paddy Field Soil

Paddy field soil is a natural habitat for many Cyanobacteria. Generally Heterocystous form dominate the nitrogen deficient soil. Non-heterocystous forms are also known to fix nitrogen. The diversity and the distribution of these forms vary. 20 Soil samples were serial diluted in BG-11 devoid of nitrogen supplement. Later the colonies were streaked to obtain axenic culture. The soil pH was also determined to study the effect on the diversity. The relative abundance of the BGA species was determined .Diversity of non-heterocystous form in the paddy field was found to be dominated by filamentous BGA, Lynbgya by 21%, Oscillatoria and Phormidium by 17% and colonial form Chrococcus sp by 12.5% Followed by Myxosarcina sp., 8%, while Aphanocapsa sp., Chlorogloea sp., Crinaluim sp., Gleocapsa sp, Plectonema sp. and Schizothrix sp., were 4%. A majority of the non-heterocystous BGA were found in the soil which had a pH ranging between 8.2-8.6. Diversity study of non-heterocystous BGA can help in understanding the distribution and further aid in the study of nitrogen fixation in these forms.

Nitrogen-fixing Are polyploidy and host peptide-governed symbiont differentiation universal characteristics of endosymbiosis in the Rhizobium-legume symbiosis?

Legumes may have a symbiotic relationship with nitrogen-fixing bacteria, they can grow in nitrogen-deficient soils. There is a lot of interest in applying what we've learned about this symbiosis to non-symbiotic plants. An international study group has progressed in their understanding of this complicated biological process. Microbes play a crucial role in all creatures, including plants, whether they are useful or detrimental. Plant viability depends on the ability to monitor the bacteria in the environment.

Morphometric analysis and characterization of the nutritional quality in African yam bean accessions

Underutilized crops with rich nutritional base in addition to high seed yield are currently promoted in reducing hunger and malnutrition ravaging Africans. Identifying specific accessions with rich genetic bases provide information for developing biofortified legumes. Fourteen morphological and two nutritional traits of 23 African yam bean accessions were assessed under a replicated field trial in one location over 4 years. Analysis of variance revealed significant variations for most traits with high genotypic correlation coefficients. Genotypic coefficient of variation was high for maturity date (59.95%), protein content (60.78%), tuber yield per plant (67.33%) and number of seeds per pod (77.22%). Seed yield did not correlate with protein and oil content, indicating that nutritional traits were independent of seed yield traits. Heritability was high for most traits but moderate for protein and oil content. First order predictor variables, identified number of seeds per pod, and pod traits to directly affect seed and tuber yield. First seven principal components axes explained 67% of total variation including nutritional traits. Four distinct accession clusters at the R-squared distance of 0.45 similarity index were identified. Simultaneous improvement in earliness, yield, protein and oil contents are achievable by selecting parents from clusters I and II. The only accession in cluster III (TSs12) produced nodules in addition to average seed yield, protein and oil content, and could be selected for cultivation in nitrogen deficient soils. Wide diversity in these accessions can be maximized for developing acceptable African yam bean varieties with enhanced yield and nutritional value.

Harnessing Rhizobia to Improve Heavy-Metal Phytoremediation by Legumes.

Rhizobia are bacteria that can form symbiotic associations with plants of the Fabaceae family, during which they reduce atmospheric di-nitrogen to ammonia. The symbiosis between rhizobia and leguminous plants is a fundamental contributor to nitrogen cycling in natural and agricultural ecosystems. Rhizobial microsymbionts are a major reason why legumes can colonize marginal lands and nitrogen-deficient soils. Several leguminous species have been found in metal-contaminated areas, and they often harbor metal-tolerant rhizobia. In recent years, there have been numerous efforts and discoveries related to the genetic determinants of metal resistance by rhizobia, and on the effectiveness of such rhizobia to increase the metal tolerance of host plants. Here, we review the main findings on the metal resistance of rhizobia: the physiological role, evolution, and genetic determinants, and the potential to use native and genetically-manipulated rhizobia as inoculants for legumes in phytoremediation practices.

Response of Bradyrhizobium japonicum nodule variables to cucurbitacin-containing phytonematicides in cowpea (Vigna unguiculata L.) on N-deficient soil

The Curve-fitting Allelochemical Response Data (CARD) had been adopted to develop the non-phytotoxic concentration of phytonematicides, technically referred to as the mean concentration stimulation point (MCSP). The MCSP for cucurbitacin-containing phytonematicides on Bradyrhizobium-nodulated legume crops had not been documented in low-input agricultural farming systems. The objective of this study was to determine the MCSP values of Nemarioc-AL and nemafric-BL phytonematicides on B. japonicum-nodulated cowpea (Vigna unguiculata) on nitrogen-deficient soils. Inoculated cowpea seeds were sown in 20-cm diameter plastic pots containing steam-pasteurised N-deficient loamy soil and Hygromix at 3: 1 (v/v) ratio. Two parallel experiments comprised Nemarioc-AL and Nemafric-BL phytonematicides, each had seven treatments (0, 2, 4, 8, 16, 32 and 64%) and applied once weekly. At 56 days after the treatments, the MCSP values for Nemarioc-AL and Nemafric-BL phytonematicides on cowpea were 5.4 and 6.3%, respectively, with the overall sensitivity (Σk) of one for each phytonematicide. In conclusion, the observed MCSP and Σk values suggested that the two cucurbitacin-containing phytonematicides were suitable for Bradyrhizobium-nodulated cowpea production systems on N-deficient soils.

Assessing the degradation efficacy of native PAH-degrading bacteria from aged, weathered soils in an Australian former gasworks site

The large-scale degradation of polycyclic aromatic hydrocarbons (PAHs) by bacteria represents a promising soil remediation strategy. The aim of this study was to identify bacterial isolates for potential use in the remediation of PAH-contaminated sites using selective isolation plating, Biolog™ MT2 evaluation and metabolic profiling on the Biolog™ system. Thirty-five bacterial isolates were isolated from aged, weathered PAH-contaminated soil using Bushnell Hass medium amended with phenanthrene as the sole carbon source. Selected isolates that were then able to grow on at least one of three model PAHs (naphthalene, phenanthrene and pyrene) were identified and then screened for their potential application in the bioremediation of aged, weathered soils from a former gasworks site based on Biolog™ MT2 data. The 16S rRNA gene sequencing showed that hydrocarbon degrading isolates were affiliated to Rhodococcus sp., Achromobacter sp., Oerskovia paurometabola, Pantoea sp., Sejongia sp., Microbacterium maritypicum and Arthrobacter equi. Enzyme studies confirmed catechol 1,2-dioxygenase activity in all of the isolates. Biolog™ Eco plates, applied in this study to evaluate the metabolic properties of seven isolates showed that all of these isolates could use a wide range of organic substrates, Sejongia sp. being the highest (28 of 31 substrates). Furthermore, the metabolic patterns of seven isolates on different substrates were summarized according to the biochemical categories of the substrates present on Biolog™ Eco plates. The isolates showed diverse performance on different biochemical categories (amino acids, phenolic compounds, amines, carbohydrates, carboxylic acids and polymers). An insight into the mechanisms by which selected bacteria degrade model PAHs and survive in nitrogen deficient soils was obtained. This study demonstrates the functional potential of indigenous bacteria for model PAHs-degradation and bioremediation of aged, weathered PAH contaminated sites of Australia.

Influence of Nitrogen Availability on Growth of Two Transgenic Birch Species Carrying the Pine GS1a Gene.

An alternative way to increase plant productivity through the use of nitrogen fertilizers is to improve the efficiency of nitrogen utilization via genetic engineering. The effects of overexpression of pine glutamine synthetase (GS) gene and nitrogen availability on growth and leaf pigment levels of two Betula species were studied. Untransformed and transgenic plants of downy birch (B. pubescens) and silver birch (B. pendula) were grown under open-air conditions at three nitrogen regimes (0, 1, or 10 mM) for one growing season. The transfer of the GS1a gene led to a significant increase in the height of only two transgenic lines of nine B. pubescens, but three of five B. pendula transgenic lines were higher than the controls. In general, nitrogen supply reduced the positive effect of the GS gene on the growth of transgenic birch plants. No differences in leaf pigment levels between control and transgenic plants were found. Nitrogen fertilization increased leaf chlorophyll content in untransformed plants but its effect on most of the transgenic lines was insignificant. The results suggest that birch plants carrying the GS gene use nitrogen more efficiently, especially when growing in nitrogen deficient soil. Transgenic lines were less responsive to nitrogen supply in comparison to wild-type plants.

English

Optimization of land use can be attained by incorporating technologies to crop production, such as the use of diazotrophic bacteria, fertilizers, and pesticides. Seed inoculation with Azospirillum is an alternative that favors the incorporation of green agriculture in regions of conventional farming, such as the Brazilian savannah (Cerrado). However, limited information is available about this bacterium’s contribution to agriculture when other technologies are also incorporated. This study evaluated the performance of maize hybrids inoculated, or not, with Azospirillum brasilense, with or without fungicide applications, and subjected to different nitrogen rates under Cerrado field conditions. Each factor analyzed contributes to the increased maize grain yield. The use of inoculants containing plant growth promoting bacteria is a good option to ensure high yield of maize. Still, nitrogen should not be replaced, neither totally nor partially, by seed inoculation with Azospirillum. Fungicide applications should be done, as required, during maize cycle. Moreover, specific maize breeding programs should consider the affinity between Azospirillum strains and maize hybrids, mainly for regions with nitrogen deficient soils, like Cerrado. Thus, by incorporating additional technologies, maize crop farmers can optimize land use and, consequently, reduce the expansion into new agricultural areas. Key words: Foliar protection, nitrogen use, plant growth promoting bacteria, sustainability, Zea mays L.

Growth and yield responses of cotton (Gossypium hirsutum) to inorganic and organic fertilizers in southern Malawi

Fertilizer trees, the nitrogen-fixing legumes, such as gliricidia (Gliricidia sepium) and tephrosia (Tephrosia spp.) have been used to improve soil fertility for higher crop yields in nitrogen deficient soils. Many studies have focused on how these fertilizer trees improve maize yield, but there has been a dearth of information on the effect of fertilizer tree species on cotton growth and yield. A study was undertaken for two cropping seasons (2012/13 and 2013/14) with the objective of assessing IRM 81 cotton growth and yield responses to tephrosia and/or gliricidia biomass with or without inorganic fertilizer application. Boll opening significantly varied (P < 0.0001) with treatments and early boll opening was observed in plots where only inorganic fertilizer was applied. Higher lint yield (mean of 1397 kg/ha) was obtained in the second cropping season than in the first cropping season (480 kg/ha) and the application of gliricidia biomass with fertilizer gave the highest lint yield (2121 kg/ha). The lowest lint and seed yields were obtained from plots where tephrosia biomass only was applied. It is concluded that the use of gliricidia biomass with inorganic fertilizer improved cotton yields. The high amount of gliricidia biomass (due to prolific coppicing) applied contributed to higher cotton lint yields with reduced rates of inorganic fertilizer application, making gliricidia-cotton intercropping a cost-effective option to smallholder farmers.