Maize Shoot Growth Research Articles

Plant Age and Soil Texture Rather Than the Presence of Root Hairs Cause Differences in Maize Resource Allocation and Root Gene Expression in the Field.

Understanding the biological roles of root hairs is key to projecting their contributions to plant growth and to assess their relevance for plant breeding. The objective of this study was to assess the importance of root hairs for maize nutrition, carbon allocation and root gene expression in a field experiment. Applying wild type and root hairless rth3 maize grown on loam and sand, we examined the period of growth including 4-leaf, 9-leaf and tassel emergence stages, accompanied with a low precipitation rate. rth3 maize had lower shoot growth and lower total amounts of mineral nutrients than wild type, but the concentrations of mineral elements, root gene expression, or carbon allocation were largely unchanged. For these parameters, growth stage accounted for the main differences, followed by substrate. Substrate-related changes were pronounced during tassel emergence, where the concentrations of several elements in leaves as well as cell wall formation-related root gene expression and C allocation decreased. In conclusion, the presence of root hairs stimulated maize shoot growth and total nutrient uptake, but other parameters were more impacted by growth stage and soil texture. Further research should relate root hair functioning to the observed losses in maize productivity and growth efficiency.

Localized nutrient supply promotes maize growth and nutrient acquisition by shaping root morphology and physiology and mycorrhizal symbiosis

Localized nutrient supply can induce maize (Zea mays L.) root proliferation, and then promote nutrient uptake. Yet, how maize plants adjust root morphology, physiology and mycorrhizal symbiosis to efficiently capture nutrients in different heterogeneous environments remains largely unknown. A 2-year field experiment with maize was conducted with localized application of ammonium (N, nitrogen) and phosphorus (P) (LNP); N and P mixed with controlled-release fertilizer (LCF); N and P mixed with organic fertilizer (LOF); diammonium phosphate (LADP) or broadcast N and P application. Our results showed that root length density was 230–584 % larger, root respiration rate was 97–115 % greater, pH value was decreased by 1.61–1.99 units, activity of acid phosphatase activity was 21–36 % higher, mycorrhizal colonization was 19–35 % lower and hyphal length density was 39–69 % lower in localized compared with broadcast nutrient supply. The root morphological and physiological and mycorrhizal fungi responses were tightly associated with improved maize shoot growth and nutrition accumulation. In addition, localized nutrient application at high nutrient rate (e.g. LCP and LOF treatment) had a more strongly positive effect on root proliferation, shoot growth and/or nutrient accumulation compared with broadcast application, especially at later growth stages of maize. Our findings indicate that localized nutrient application can improve nutrient-use efficiency via strengthening positive cooperativity between root morphological and physiological traits, and shaping trade-off between root growth and mycorrhizal symbioses.

Root hairs matter at field scale for maize shoot growth and nutrient uptake, but root trait plasticity is primarily triggered by texture and drought

AimsRoot hairs are important for uptake, especially for nutrients with low mobility in soils with high sorption capacity. Mutants with defective root hairs are expected to have lower nutrient uptake, unless they compensate with more root growth. Since root hairs can also contribute to the plant's water uptake their importance could change over the course of a growing season. It was our objective to investigate the role of root hairs under field conditions.MethodsThe root hair mutant rth3 of Zea mays and the corresponding wild-type were grown for two years under field conditions on sand and loam.ResultsShoot growth and P and K uptake of the plants were promoted by the presence of hairs at all growth stages. Differences between genotypes were greater on loam than on sand until tassel emergence, presumably as additional exploitation by hairs is more relevant in loam. Compensation for the absence of root hairs by increased root growth was not observed in absolute terms. The root to shoot ratio was higher for rth3 than for wild-type. Root traits showed high plasticity in response to texture, the most salient being a greater mean root diameter in sand, irrespective of genotype. The mechanism causing the increase in mean root diameter is still unknown. Root length density was higher in sand, which can be explained by a greater need for exploration than exploitation in this substrate.ConclusionThe role of hairs for nutrient uptake could be confirmed under field conditions. The large impact of texture on root growth and consequences for carbon balance require further investigations.

Mulch and no-till impacts on nitrogen and phosphorus leaching in a maize field under sub-tropic monsoon climate

Mulching and no-till are recommended practices to conserve soil water and soil health, but their effects on nutrient leaching in maize fields under monsoon rainfall need to be assessed. Soil water, soil temperature, and root and shoot growth of maize under plastic mulch, straw mulch, and no-till treatments were observed. Nitrogen (N) and phosphorus (P) leaching below a 110-cm deep lysimeter after heavy rainfall events were determined. The mulching and no-till treatments increased soil water content by 0.022–0.025 cm3/cm3 and reduced daytime soil temperature by 0.5–2.6 °C. Average leaching concentrations of total N and available P at 63 and 93 DAS (days after sowing) were 2.4 and 4.9 mg N/L and 0.12 and 0.08 mg P/L, respectively. For the control condition, the leaching concentrations of N and P decreased between 63 and 93 DAS. The mulching treatments did not influence nutrient leaching load at 63 DAS, but at 93 DAS the N leaching load increased by 181–248 g/ha and P load by 3.1–4.9 g/ha compared with the control treatment. The mulch treatments had taller shoots (5.1–18.3 cm) and a higher root-shoot ratio. The higher soil water content in the mulched treatments facilitated nutrient redistribution, plant growth, nutrient transport, and leaching. No-till increased N leaching by 103 g N/ha per leaching event but not P leaching. The no-till treatment had shorter shoots but longer roots than the conventional tillage treatment due to poor nutrient redistribution in the no-till soil. A modification in the nutrient management plan is needed to better control nutrient redistribution and minimize leaching.

Silicon-mediated growth promotion in maize (Zea mays L.) occurs via a mechanism that does not involve activation of the plasma membrane H+-ATPase

Silicon (Si)-mediated growth promotion of various grasses is well documented. In the present study, Si-induced changes in maize shoot growth and its underlying mechanisms were studied. Maize plants were grown with various concentrations of Si (0–3 mM) in the nutrient solution. Silicon nutrition improved plant expansion growth. Silicon-supplied maize plants (0.8 and 1.2 mM) showed higher plant height and leaf area compared to no-Si amended plants. It was assumed that Si-induced expansion growth was due to positive Si effects on plasma membrane (PM) H+-ATPase. In this context, western blot analysis revealed an increase in PM H+-ATPase abundance by 77% under Si nutrition. However, in vitro measurements of enzyme activities showed no significant effect on apoplast pH, proton pumping, passive H+ efflux and enzyme kinetics such as Km, Vmax, and activation energy. Further, these results were confirmed by in vivo ratiometric analysis of apoplastic pH, which showed non-significant changes upon Si supply. In contrast, 1 mM Si altered the relative transcripts of specific PM H+-ATPase isoforms. Silicon application resulted in a significant decrease of MHA3, and this decrease in transcription seems to be compensated by an increased concentration of H+-ATPase protein. From these results, it can be concluded that changes in cell wall composition and PM H+-ATPase may be responsible for Si-mediated growth improvement in maize.

Effects of solar radiation on root and shoot growth of maize and the quantitative relationship between them

AbstractSolar radiation is an important environmental factor affecting maize (Zea maysL.) root and shoot growth and grain yield. This study was conducted in Qitai and Yinchuan, China, in 2018 and 2019. The maize cultivars of XY335, ZD958, and DH618 and planting densities of 7.5 × 104(D1) and 12 × 104plants ha−1(D2) were adopted under shading levels of 15 (S1), 30 (S2), and 50% (S3) with natural light as the control (CK). The results showed that averaging all shading and density treatments over the 2 yr, shading reduced the grain yields of XY335, ZD958, and DH618 by an average of 40.4, 39.2, and 35.6%, respectively, compared with the CK. The effect of solar radiation on the root dry weight was greater than that on the shoot dry weight, which resulted in a decrease in root/shoot ratio with increasing shading level. The quantitative analysis results showed that for every 1‐MJ m−2decrease in solar radiation, the root dry weight, shoot dry weight, and root/shoot ratio decreased by 0.1938 g m−2, 1.3517 g m−2, and 0.0103 × 10−2, respectively. According to this quantitative relationship, it was helpful to select cultivars and planting density with suitable root characteristics under different solar radiation conditions in different regions. From the aspects of shoot and grain yield, DH618 was more shade resistant, and its root system rapidly adjusted to compensate for shoot growth and yield formation when solar radiation decreased. Such cultivars should be given attention in future production and breeding.

Pathogenicity of Pythium species to maize

Pythium isolates from diseased and dead bait plants of maize and cress grown in compost or various soils (maize fields, parkland under deciduous trees, grassland) were characterised and tested for pathogenicity to maize (Zea mays L.). In pot tests performed under controlled conditions, pathogenicity of the isolates to maize was apparent by reduction of root and shoot growth, whereas damping-off of maize seedlings was less frequent. Contrarily, pea seedlings were killed by pathogenic Pythium isolates. Pythium isolates from diseased maize seedlings and pathogenic strains from other gramineous plants (P. phragmitis, P. aff.phragmitis, P. catenulatum) were not necessarily more virulent to maize compared to isolates originating from dicotyledonous plants (cress). The most virulent isolates originated from compost and caused a reduction of maize shoot growth of up to 60%. Phylogenetic analysis revealed that they were very closely related to P. ultimum var. ultimum and P. arrhenomanes, respectively. Isolates originating from maize fields, grassland and parkland under deciduous trees, a reference culture of P. arrhenomanes and strains of P. phragmitis, P. aff. phragmitis and P. catenulatum with known pathogenicity on reed were non-pathogenic on maize. Isolates from compost, and from maize fields generally had a higher temperature optimum for mycelial growth (30 °C) and a faster growth rate (1.5–2.0 mm h−1) compared to the isolates from parkland under deciduous trees and grassland soil (20–25 °C, ~1.0 mm h−1), respectively. This study indicates a potential impact of pathogenic Pythium on maize plants even in the absence of visible symptoms.

Gibberellins and Heterosis in Crops and Trees: An Integrative Review and Preliminary Study with Brassica.

Heterosis, or hybrid vigor, has contributed substantially to genetic improvements in crops and trees and its physiological basis involves multiple processes. Four associations with the phytohormone gibberellin (GA) indicate its involvement in the regulation of heterosis for shoot growth in maize, sorghum, wheat, rice, tomato and poplar. (1) Inbreds somewhat resemble GA-deficient dwarfs and are often highly responsive to exogenous GA3. (2) Levels of endogenous GAs, including the bioeffector GA1, its precursors GA19 and GA20, and/or its metabolite GA8, are higher in some fast-growing hybrids than parental genotypes. (3) Oxidative metabolism of applied [3H]GAs is more rapid in vigorous hybrids than inbreds, and (4) heterotic hybrids have displayed increased expression of GA biosynthetic genes including GA 20-oxidase and GA 3-oxidase. We further investigated Brassica rapa, an oilseed rape, by comparing two inbreds (AO533 and AO539) and their F1 hybrid. Seedling emergence was faster in the hybrid and potence ratios indicated dominance for increased leaf number, area and mass, and stem mass. Overdominance (heterosis) was displayed for root mass, leading to slight heterosis for total plant mass. Stem contents of GA19,20,1 were similar across the Brassica genotypes and increased prior to bolting; elongation was correlated with endogenous GA but heterosis for shoot growth was modest. The collective studies support a physiological role for GAs in the regulation of heterosis for shoot growth in crops and trees, and the Brassica study encourages further investigation of heterosis for root growth.

Early priority effects of occupying a nutrient patch do not influence final maize growth in intensive cropping systems

Priority effects can be caused by an individual plant within a population that is the first to occupy and explore nutrient patches. However, the magnitude of priority effects of exploring a nutrient patch on plant growth during the ontogeny remains obscure. A 30-day rhizo-box experiment and a 2-year field trial with maize (Zea mays L) were conducted to examine the influence of priority effects arising from heterogeneous nutrient (nitrogen and phosphorus) supply on the root and shoot growth of maize under nutrient-limited and nutrient-rich environments. In the rhizo-box with limited soil resources, maize shoot biomass and nutrient content increased with the closeness to the nutrient patch, suggesting strong priority effects. In the field trial with high fertilizer input, priority effects arising from root proliferation within the nutrient patch also brought growth advantages for individual plants close to the patch in the first 45 days after sowing (DAS), but positive effects were weaker than in rhizo-box conditions. The growth advantage was not maintained after 60 DAS. The early priority effects did not promote grain yield. Our findings demonstrated that the growth advantage of early priority effects from exploring the nutrient patch was dependent on time and soil nutrient supply.

Effects of soil pH on the competitive uptake of amino acids by maize and microorganisms

Organic nitrogen can play an important role in plant growth, and soil pH changed greatly due to the over-use of chemical fertilizers, but the effects of soil pH on the competitive uptake of amino acids by plants and rhizosphere microorganisms are lack of detailed research. To study the effects of soil pH on the uptake of amino acids by maize and soil microorganisms, two soils from Hangzhou and Tieling were selected, and the soil pH was changed by the electrokinesis, then the 15N-labeled glycine was injected to the centrifuge tube with a short-term uptake of 4 h. Soil pH had a significant effect on the shoot and root biomass, and the optimal pH for maize shoot growth was 6.48 for Hangzhou red soil, while it was 7.65 for Tieling brown soil. For Hangzhou soil, the 15N abundance of maize shoots under pH=6.48 was significantly higher than under other treatments, and the uptake amount of 15N-glycine was also much higher. However, the 15N abundance of maize shoots and roots under pH=7.65 Tieling soil was significantly lower than it under pH=5.78, but the uptake amount of 15N-glycine under pH=7.65 was much higher. The microbial biomass C was much higher in pH=6.48 Hangzhou soil, while it was much lower in pH=7.65 Tieling soil. According to the results of root uptake, root to shoot transportation, and the competition with microorganisms, we suggested that although facing the fierce competition with microorganisms, the maize grown in pH=6.48 Hangzhou soil increased the uptake of glycine by increasing its root uptake and root to shoot transportation. While in pH=7.65 Tieling soil, the activity of microorganisms was decreased, which decreased the competition with maize for glycine, and increased the uptake of glycine by maize.

Allelochemicals as Growth Stimulators for Drought Stressed Maize

Sorgaab, an aqueous extract of sorghum leaves was applied to probe the modulation in growth and physiological attributes of maize under drought in lab and greenhouse studies. Sorgaab soaked seeds (10 dilutions) were germinated to assess drought tolerance at germination and seedling growth stages. More concentrated Sorgaab solutions (2 mL·L-1) were damaging, while lower concentration in the range of 0.75 to 1.5 mL·L-1 improved the root and shoot growth of maize under drought. Applied drought stress decreased chlorophyll b greater than chlorophyll a that improved the chl a/b ratio. Application of Sorgaab also improved the internal CO2 assimilation, which increased the net photosynthesis and A/E ratio of drought affected plants. Soluble phenolics and anthocyanins were also more increased in plant receiving Sorgaab under drought than control. Although greater concentrations of phenolic acids inhibit the uptake of ions, but its lower concentrations stimulate the uptake of K+, Ca2+, NO3, PO4. In conclusion, although high concentrations of Sorgaab reduced the growth of plants, it might alleviate the adverse effects of drought, if applied at the low concentration. Dilute concentrations of Sorgaab can be utilized as a natural source for improving drought resistance in maize both at germination and later growth stages.

Phytoavailability and Leachability of Heavy Metals from Contaminated Soil Treated with Composted Livestock Manure

ABSTRACTA study was carried out with maize as the test crop to investigate the bioavailability and leachability of heavy metals (HM) from HM-contaminated soils treated with composted manure. The application of composted manure increased the maize shoot growth by 32.3% and root growth by 30.5% compared with fresh manure. The concentration of HM in maize shoot varied in the order lead (Pb) > nickel (Ni) > zinc (Zn) > chromium (Cr) > copper (Cu) > cadmium (Cd). Whether for the shoot or root, the heavy metal concentrations decreased as the length of manure composting increased, but concentrations were higher in the root than the shoot. Composting decreased the bioavailability and leachability of HM and, hence, their export to the environment more effectively than direct use of fresh manure. Thus, the use of composted manure in place of fresh manure in polluted soils would be more beneficial for mitigating HM pollution.

Severity and duration of osmotic stress on partial root system: effects on root hydraulic conductance and root growth

Effects of severity and duration of osmotic stress on partial root system were investigated on root hydraulic conductance (L p ) and growth in each sub-root system. The maize seedlings were raised in nutrient solution with the roots divided equally into two containers. At 12 days after transplanting, half of root system was subjected to osmotic stress of −0.2, −0.4 and −0.6 MPa using PEG 6000 added in the solution, and no PEG 6000 solution was taken as control (CK). L p and root growth in each sub-root system were measured at 0, 0.25, 0.5, 1, 3, 5, 7 and 9 days after treatment (DAT). Results show that compared to CK, −0.2 MPa treatment enhanced the hydraulic conductance per root area (L pr ) in non-stressed sub-root system by 12 % at 0.5 DAT. In −0.4 MPa treatment, L pr in non-stressed sub-root system was significantly increased at 9 DAT. But in −0.6 MPa treatment, significant decrease of 12–40 % was observed in non-stressed sub-root system during 0.5–3 DAT if compared to CK, indicating that the threshold of osmotic stress for the compensatory effect of water uptake in non-stressed sub-root system was between −0.2 and −0.4 MPa. In addition, the root area growth rate in non-stressed sub-root system was significantly higher than that in CK during 0.25–0.5, 1–3 and 5–7 DAT for −0.2, −0.4 and −0.6 MPa treatments, respectively. Similar trend also was observed for root length growth rate, indicating that osmotic stress could still stimulate the compensatory effect of root growth other than water uptake under partial root system. Moreover, the occurrence of such compensatory effect delayed with the increasing osmotic stress. Meanwhile, −0.2 MPa treatment had no significant effect on maize shoot growth but −0.4 and −0.6 MPa treatments inhibited shoot biomass accumulation, which resulted in higher root/shoot ratio in −0.4 and −0.6 MPa treatments. Thus root plasticity in hydraulic conductance and root growth in different root zones varied largely depending on the severity and duration of osmotic stress under partial root system.

Increased soil phosphorus availability induced by faba bean root exudation stimulates root growth and phosphorus uptake in neighbouring maize.

Root growth is influenced by soil nutrients and neighbouring plants, but how these two drivers affect root interactions and regulate plant growth dynamics is poorly understood. Here, interactions between the roots of maize (Zea mays) and faba bean (Vicia faba) are characterized. Maize was grown alone (maize) or with maize (maize/maize) or faba bean (maize/faba bean) as competitors under five levels of phosphorus (P) supply, and with homogeneous or heterogeneous P distribution. Maize had longer root length and greater shoot biomass and P content when grown with faba bean than with maize. At each P supply rate, faba bean had a smaller root system than maize but greater exudation of citrate and acid phosphatase, suggesting a greater capacity to mobilize P in the rhizosphere. Heterogeneous P availability enhanced the root-length density of maize but not faba bean. Maize root proliferation in the P-rich patches was associated with increased shoot P uptake. Increased P availability by localized P application or by the presence of faba bean exudation stimulated root morphological plasticity and increased shoot growth in maize in the maize/faba bean mixture, suggesting that root interactions of neighbouring plants can be modified by increased P availability.

Bacteria in combination with fertilizers promote root and shoot growth of maize in saline-sodic soil.

Salinity is the leading abiotic stress hampering maize ( Zea mays L.) growth throughout the world, especially in Pakistan. During salinity stress, the endogenous ethylene level in plants increases, which retards proper root growth and consequent shoot growth of the plants. However, certain bacteria contain the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which converts 1-aminocyclopropane-1-carboxylic acid (an immediate precursor of ethylene biosynthesis in higher plants) into ammonia and α-ketobutyrate instead of ethylene. In the present study, two Pseudomonas bacterial strains containing ACC-deaminase were tested separately and in combinations with mineral fertilizers to determine their potential to minimize/undo the effects of salinity on maize plants grown under saline-sodic field conditions. The data recorded at 30, 50 and 70 days after sowing revealed that both the Pseudomonas bacterial strains improved root and shoot length, root and shoot fresh weight, and root and shoot dry weight up to 34, 43, 35, 71, 55 and 68%, respectively, when applied without chemical fertilizers: these parameter were enhanced up to 108, 95, 100, 131, 100 and 198%, respectively, when the strains were applied along with chemical fertilizers. It can be concluded that ACC-deaminase Pseudomonas bacterial strains applied alone and in conjunction with mineral fertilizers improved the root and shoot growth of maize seedlings grown in saline-sodic soil.

Evolution of US maize (Zea mays L.) root architectural and anatomical phenes over the past 100 years corresponds to increased tolerance of nitrogen stress.

Increasing the nitrogen use efficiency of maize is an important goal for food security and agricultural sustainability. In the past 100 years, maize breeding has focused on yield and above-ground phenes. Over this period, maize cultivation has changed from low fertilizer inputs and low population densities to intensive fertilization and dense populations. The authors hypothesized that through indirect selection the maize root system has evolved phenotypes suited to more intense competition for nitrogen. Sixteen maize varieties representing commercially successful lines over the past century were planted at two nitrogen levels and three planting densities. Root systems of the most recent material were 7 º more shallow, had one less nodal root per whorl, had double the distance from nodal root emergence to lateral branching, and had 14% more metaxylem vessels, but total mextaxylem vessel area remained unchanged because individual metaxylem vessels had 12% less area. Plasticity was also observed in cortical phenes such as aerenchyma, which increased at greater population densities. Simulation modelling with SimRoot demonstrated that even these relatively small changes in root architecture and anatomy could increase maize shoot growth by 16% in a high density and high nitrogen environment. The authors concluded that evolution of maize root phenotypes over the past century is consistent with increasing nitrogen use efficiency. Introgression of more contrasting root phene states into the germplasm of elite maize and determination of the functional utility of these phene states in multiple agronomic conditions could contribute to future yield gains.

Root Growth of Neighboring Maize and Weeds Studied with Minirhizotrons

Competition between crops and weeds may be stronger at the root than at the shoot level, but belowground competition remains poorly understood, due to the lack of suitable methods for root discrimination. Using a transgenic maize line expressing green fluorescent protein (GFP), we nondestructively discriminated maize roots from weed roots. Interactions between GFP-expressing maize, common lambsquarters, and redroot pigweed were studied in two different experiments with plants arranged in rows at a higher plant density (using boxes with a surface area of 0.09 m2) and in single-plant arrangements (using boxes with a surface area of 0.48 m2). Root density was screened using minirhizotrons. Relative to maize that was grown alone, maize root density was reduced from 41 to 87% when it was grown with redroot pigweed and from 27 to 73% when it was grown with common lambsquarters compared to maize grown alone. The calculated root : shoot ratios as well as the results of shoot dry weight and root density showed that both weed species restricted root growth more than they restricted shoot growth of maize. The effect of maize on the root density of the weeds ranged from a reduction of 25% to an increase of 23% for common lambsquarters and a reduction of 42 to 6% for redroot pigweed. This study constitutes the first direct quantification of root growth and distribution of maize growing together with weeds. Here we demonstrate that the innovative use of transgenic GFP-expressing maize combined with the minirhizotron technique offers new insights on the nature of the response of major crops to belowground competition with weeds.

Root growth in response to nitrogen supply in Chinese maize hybrids released between 1973 and 2009

Root growth has a fundamental role in nitrogen (N) use efficiency. Nevertheless, little is known about how modern breeding progress has affected root growth and its responses to N supply. The root and shoot growth of a core set of 11 representative Chinese maize (Zea mays L.) hybrids released between 1973 and 2009 were investigated under high N (4 mmol L(-1), HN) and low N (0.04 mmol L(-1), LN) levels in a solution culture system. Compared with LN, HN treatment decreased root dry weight (RDW), the root: shoot ratio (R/S), and the relative growth rate for root dry weight (RGR(root)), but increased the total root length (TRL) and the total lateral root length (LRL). The total axial root length (ARL) per plant was reduced under HN, mostly in hybrids released before the 1990s. The number of seminal roots (SRN) was largely unaffected by different N levels. More recently released hybrids showed higher relative growth rates in the shoot under both HN and LN. However, the roots only showed increased RGR under HN treatment. Correspondingly, there was a positive linear relationship with the year of hybrid release for TRL, LRL and ARL under HN treatment. Together, these results suggest that while shoot growth of maize has improved, its root growth has only improved under high N conditions over the last 36 years of selective breeding in China. Improving root growth under LN conditions may be necessary to increase the N use efficiency of maize.

Root and Shoot Growth of Maize (Zea mays) as Affected by Incorporation of Crotalaria juncea and Tithonia diversifolia as Green Manures

AbstractCrop establishment, determined by shoot and root growth during early growth is a vital component in procuring desired plant populations and high yields in rainfed tropical smallholder farming systems, where green manures help maintain soil fertility and sustainability. As green manure incorporation could affect early seedling growth, studies were conduced in a plant house using soils from fields, to evaluate the impact of incorporating two popular tropical green manures (Crotalaria juncea and Tithonia diversifolia) into soil under rainfed field conditions over 3 years, on selected physico‐chemical properties of the soils and on establishment and early shoot and root growth of maize (Zea mays), with and without inorganic fertilizers. In a given year, green manure was grown in one season while maize was grown in the other. A soil that did not receive green manures but was left fallow during the period of green manure cultivation was used as the control treatment. The incorporation of green manures over the 3 years showed trends of increasing soil physical properties, and also the available nitrogen, phosphorus and potassium contents. Incorporation of Crotalaria, with its higher nitrogen content, promoted shoot growth, while Tithonia induced the development of an extended root system. The use of inorganic fertilizers stimulated the beneficial impact of the green manures in promoting shoot and root growth. The use of green manures, especially Tithonia, promoted the development of seminal and nodal roots of maize seedlings, both in the form of length and thickness (based on root surface area) and root length densities, which could assist in successful crop establishment and resource utilization, rather than primary roots. The benefits of using green manures, especially Tithonia, in promoting root growth and Crotalaria in shoot development of maize seedlings even without inorganic fertilizers is presented.

Early phosphorus nutrition, mycorrhizae development, dry matter partitioning and yield of maize

We conducted a field experiment to test the hypothesis that improved phosphorus nutrition occurs in maize plants with rapid arbuscular (AM) mycorrhizae development at early developmental stages and that this also is reflected in dry matter allocation and final yield. A split-split plot design was used with previous crop (Zea mays L.-maize and Brassica napus L.-canola), tillage practices (no-tillage or conventional tillage) and P fertilization (5 levels) as factors chosen to modify mycorrhizae development at early developmental stages of maize. Previous cropping with canola resulted in decreased shoot-P concentration and shoot growth of maize at early stages. No-tillage resulted in higher shoot-P concentration but lower shoot weight than conventional tillage. Greater shoot-P uptake was related to a rapid intraradical development of mycorrhizae (previous crop of maize) or rapid connection to a mycorrhizal mycelium network (no-tillage treatments). Maize yield and harvest index were lower after cropping with canola. The yield for conventional tillage was higher than that for no-tillage but the harvest index was lower. The hypothesis was supported at early stages of maize growth by the effect of previous crop but not by results of tillage, because an unknown factor reduced growth in the no-tillage system. The hypothesis was supported at maturity by increased biomass allocation to grain relative to total shoot weight in treatments with greater shoot-P concentration at early stages.