Two field trials were conducted at Giza Research Station, with split plot design with three replicates during the two successive summer seasons in 2012 and 2013. The aim of this study was to find out the effect of cotingen for covering seed by four treatments (zero, 7.5, 15 and 22.5 g kg-1 grain) and six nitrogen fertilizer levels (control, 30, 60, 90, 120 and 150 kg fed.-1) on maize yield and yield attributes of single cross 10 cultivar. Stepwise multiple linear regression analysis was used to determine the importance of yield components and to predict the yield under different levels of nitrogen and cotingen rates. Nitrogen levels exhibited significant effect for all studied traits, while cotingen were significant for100-kernels weight; shelling% and grain yield traits only. The interaction between cotingen and Nitrogen was significant for row per ear, shelling% and grain yield. Meanwhile, stepwise linear regression analysis showed that 100-kernels weight, number of kernels per row and shelling% were the most important contributing traits to yield (R2 = 82.11%). The nitrogen rates for maximum yield derived from the four statistical models (linear, logarithmic, quadratic, and exponential) describing the response of yield, using the R2statistic to select a model, which shows how each of the models fits the data. The quadratic model best described the yield responses observed in this study. Further confirms the role of nitrogen and cotingen fertilizers in increasing yield production in maize. The 5th N rate under 3rdcotingen (120 Kg fed-1 + 22.5 and 15g kg-1 grain) produced the highest yield being 34.70 and 34.65 ard. fed-1 over all treatments. This is very close to recommendations. The 4th N (90Kg fed-1) rate under any cotingen level produced higher yield than any nitrogen rate only. Economically, considering optimum N fertilization rate, 105.18 Kg fed-1 nitrogen and 22.5 g kg-1 grain cotingen was the most reasonable level. This is considerably below the current recommendation. Therefore, results confirmed that higher cotingen treatment decreased the optimal nitrogen and increased the yield.

Identification of specific physiological differences among maize genotypes (six inbred lines, four single crosses and four three-way crosses) to drought would be useful to plant breeders for improving selection criteria. Two field experiments were conducted in optimum and stress moisture conditions at Gemmeiza Agricultural Re-search Station in 2001 and 2003 growing seasons. The treatments were 14 geno-types, (six inbreds and eight hybrids), which were separately established under three irrigation treatments in split plot design with four replications. The genotypes were compared under water-deficit conditions on the basis of certain rapid techniques to determine leaf area index (LAI), photosynthetic efficiency (photo), canopy tempera-ture depression (CTD), stomatal conductance (SC) and chlorophyll (CHL) content which were deleteriously affected by water stress in the sensitive genotypes. Results revealed that values of LAI, photosynthetic efficiency, canopy temperature depres-sion, stomatal conductance and chlorophyll content of maize hybrids surpassed those of inbred lines. This was true at 30, 45 and 60 days after planting (DAP). Dif-ferences among maize hybrids and among inbred lines were significant at different growth stages for the same studied traits, except of the LAI for the inbreds, at 30 DAP and CTD for the hybrids at 30 as well as 60 DAP. Detecting certain physio-logical criteria, i.e. LAI, photosynthetic efficiency (photo), canopy temperature de-pression (CTD), stomatal conductance (SC) and chlorophyll content (Chl) could be used as reliable techniques to explore the physiological activity of maize genotypes at early stages of growth and may be recommended in screening different genotypes in maize breeding programs.

Two field trials were carried out at South Tahrir Research Station (Ali- Moubark). These trials were conducted in 2003 and 2004 to evaluate three planting dates of maize (the over story shade crop) intercropped with groundnut i.e, on 1st June, 10th June and 20th June, and four plant densities of maize intercropped with groundnut, i.e, maize was spaced at 50 and 100 cm apart leaving one or two plants/hill. Groundnut (the main crop) was grown on all rows. The data obtained indicate that ear length, ear diameter, number of rows/ear, number of kernels/row and the weight of 100grains increased with increasing maize spacing as well as with diminishing the number of plants remained per hill after thinning (to one plant/ hill). On other hand dense planting resulted in higher yield of maize whether by narrowing maize spacing or increasing the number of maize plants per hill after thinning. Yield and yield components of maize were significantly decreased by delaying planting date of maize up to the latest date. Yield /fed and yield components of groundnut were associated with maize density and distribution. The more the shade offered by maize the less the values of these traits were obtained. Highest values were obtained when maize was spaced at 100cm. and thinned to one plant/ hill. Increases in the values of yield and yield components of groundnut were associated with delaying the planting date of maize. Delaying the planting date of maize resulted in increases in the values of land equivalent ratio (LER) and the relative crowding coefficient. The treatment effect at any planting date of maize exerted very low competitive pressure when aggressivity was measured. With delaying seeding maize, competitive ratio (CR) diminished to the least. Spacing maize at 50cm. apart and leaving two plants / hill after thinning resulted in highest value of LER and relative crowding coefficient (RCC). Nor any maize density had any heavy competitive pressure on groundnut when aggressivity was measured