Effect of water stress at different development stages on vegetative and reproductive growth of corn
A field study was carried out from 1995 to 1997 in order to determine the effect of irrigation and water stress imposed at different development stages on vegetative growth, grain yield and other yield components of corn (Zea mays L.). The field trials were conducted on a silty loam Entisol soil, with Pioneer 3377 corn hybrid. A randomised complete block design with three replications was used. Four known growth stages of the plant were considered and a total of 16 (including rain fed) irrigation treatments were applied. The effect of irrigation or water stress at any stage of development on plant height, leaf area index, grain yield per hectare, as well number of ears per plant, grain yield per cob and 1000 kernels weight, were evaluated. Results of this 3-year study show that all vegetative and yield parameters were significantly affected by water shortage in the soil profile due to omitted irrigation during the sensitive tasselling and cob formation stages. Water stress occurring during vegetative and tasselling stages reduced plant height, as well as leaf area development. Short-duration water deficits during the rapid vegetative growth period caused 28–32% loss of final dry matter weight. Highest yields were observed in the fully irrigated control (VTCM) and the treatment which allowed water stress during the vegetative growth stage (TCM). Even a single irrigation omission during one of the sensitive growth stages, caused up to 40% grain yield losses during dry years such as 1996. Much greater losses of 66–93% could be expected as a result of prolonged water stress during tasselling and ear formation stages. Seasonal irrigation water amounts required for non-stressed production varied by year from 390 to 575 mm. Yield response factor (ky) values (unitless parameter) relating yield loss to water deficits) obtained for the first, second and third experimental years were determined to be 1.22, 1.36 and 0.81, respectively. 
Effect of different levels of humic acids on nutrient content and growth of corn (Zea mays L.)
The effect of humic acids on nutrient uptake and growth of corn plants (Zea mays L.) was investigated by growing corn in plastic growth pouches containing a Hoagland nutrient solution to which were added 0, 320, 640, 1,600 or 3,200 ppm HA, pH 7.0. The experiments were carried out in three replicates for a growing period of 16 days after germination. Humic acid was in general beneficial to shoot and root growth of corn plants. Dry matter yield in corn shoots was stimulated by HA, especially by treatments with 640 ppm HA. Nutrient uptake showed a number of differences as a result of treatments with HA. Moderate applications with HA resulted in a significant increase in N content of corn shoots, while large amounts of HA had a tendency to reduce the N concentration in corn shoots. As a result of the HA treatments, P concentrations in corn shoots were decreased, but differences in K contents were statistically nonsignificant and Mn contents in shoots were also nonsignificantly different among the treatments. However, Zn content showed a tendency to increase with increasing applications of HA. 
Noncompetitive Effects of Giant Foxtail on the Growth of Corn
Weed infestations severely reduce the yield grown corn with such yield reductions generally being attributed to competition. Noncompetitive (allelopathic) mechanisms have to date, however, received little consideration in agronomic situations. In the greenhouse, interference (competition + allelopathy) of the growth of corn (Zea mays L. Wf9 ✕ M14) by giant foxtail (Setaria faberii Herrm.) was determined in mixed culture treatments. When corn was seeded into pots with 6‐week‐old giant foxtail, corn height, fresh weight, and dry weight were reduced by as much as 90% when compared to comparable plants grown in monoculture. Competitive and allelopathic mechanisms were separated through the use of a stairstep apparatus, in which a nutrient solution passed through the rhizosphere of giant foxtail, into the rhizosphere of corn and was subsequently recycled through the system. The stairstep apparatus was used to determine the allelopathic interactions between corn and giant foxtail seedlings, mature giant foxtail, whole dead giant foxtail plants, and mascerated dead giant foxtail leaf and root material. Mature giant foxtail inhibited the growth of corn approximately 35% through an allelopathic mechanism. Elimination of competition through the use of stairsteps apparatus implicates a possible allelopathic mechanism in the interference of corn by giant foxtail that involves the exudation and leaching of phytotoxins from the roots of giant foxtail. Phytotoxins leached from dead giant foxtail reduced corn growth by as much as 50%. The relationships of allelopathy to competition, crop rotation, herbicidal activity, and physiological processes are discussed. 
Evaluation of Potential Vegetal Growth of Corn by Using Endophytic Bacteria
Aims: The study aimed to verify the potential for growth promotion of five bacterial strains to determine the best period to verify the interaction between plant and bacteria.
Study Design: The experimental design was completely randomized and the analyzes were performed at seven and fourteen days after the inoculation.
Place and Duration of Study: The experiment was performed at the biotechnology lab of the Pontifical Catholic University of Paraná, Campus Toledo.
Methodology: The strains Azospirillum brasiliense, Herbaspirillum sropedicae, Pantoea ananatis, Burkholderia ambifaria and Burkholdeira sp., were tested to growing promotion on simple hybrid corn 30F53 YH being the inoculation made in pre-germinated seeds with 106 CFU mL-1 posteriorly the same seeds were kept on genobiotic conditions with N restriction. Were evaluated the parameters aerial and root fresh weight, aerial length, root length, N percentage on aerial part, root morphology and epiphytic and endophytic population
Results: It was observed that to the seven or even the fourteen days was possible to verify the interaction between plant and bacteria by means of the parameters evaluated in other words in both periods were significant differences between treatments.
Conclusion: Bacteria were not very efficient to promising grow on the hybrid 30F53 YH in vitro on N restriction conditions since no treatment statistically overcame the control to the evaluated parameters. 
Soil Quality Dynamics during Different Growth Stages of Corn (Zea mays, L.) Cultivation in Sri Lanka
Maize known as Corn is popular among farmers as a cost effective crop with limited fertilizers. Cutting down natural forests for the planting of monocultures has had drastic impact on the soil quality leading to changes in soil properties. In Sri Lanka, no studies have been carried out to assess the effect on the properties of soil due to Maize although it is one of the extensive monoculture crops at present. The objective of the present study is to find out the effects on soil properties due to Maize cultivation during the different growth stages of the crop. This information is expected to assist in making decisions for sustainable soil management. Standard methods were used in measuring soil properties. % moisture, permeability, conductivity, Cation Exchange Capacity (CEC), the total organic carbon (Corg) and microbial biomass (Cmic) are significantly higher at seedling stage than the harvesting stage indicating possible impacts on the quality of soil. There are very little differences between growing and blooming stage for all the tested parameters. The data on effects are positively correlating with each other displaying possible consequences due to maize monoculture. The Cmic/Corg ratios of soils were low during both seedling and harvesting stages suggesting reduced number of microorganisms in soil. However, comparatively higher microbial action has been observed during both growing and blooming stages due to fertilizers. The lowest microbial respiration data during harvesting stage in the present study clearly indicates the impacts of maize plant on the biological quality of soil. Pearson’s Correlation Matrix for Soil Properties reveals that there are positive correlations for pH, Conductivity, CEC and % Organic Carbon between growth and blooming stage. Slightly negative correlation for the microbial biomass indicated that biological quality is very slowly decreasing from growth to blooming. Our results suggest that there is a very clear indication that soil is slowly deteriorating with the growth of Maize and this could lead to serious situation with continuous growth of the same plant as practiced by Sri Lankan farmers. 
 Cakir, R., 2004. Effect of water stress at different development stages on vegetative and reproductive growth of corn. Field Crops Research, 89(1), pp.1-16.
 Tan, K.H. and Nopamornbodi, V., 1979. Effect of different levels of humic acids on nutrient content and growth of corn (Zea mays L.). Plant and soil, 51(2), pp.283-287.
 Bell, D.T. and Koeppe, D.E., 1972. Noncompetitive Effects of Giant Foxtail on the Growth of Corn 1. Agronomy Journal, 64(3), pp.321-325.
 Brito, T., Portz, D. A., Pan, R. and Chaves, E. D. (2017) “Evaluation of Potential Vegetal Growth of Corn by Using Endophytic Bacteria”, Journal of Experimental Agriculture International, 19(3), pp. 1-11. doi: 10.9734/JEAI/2017/38563.
 Weerasinghe, T. K. and K. Perera, K. T. G. (2015) “Soil Quality Dynamics during Different Growth Stages of Corn (Zea mays, L.) Cultivation in Sri Lanka”, Annual Research & Review in Biology, 7(5), pp. 343-351. doi: 10.9734/ARRB/2015/18892.