Response of Two Maize Hybrids to Spatial Distribution and Nitrogenous Fertilization Rates

INTRODUCTION

Maize (Zea mays L.) is the third most important staple food crop in terms of area and production after wheat and rice in Egypt. Also, in the world, it is one of the important cereal crops in the world after wheat and rice (Gerpacio and Pingali, 2007).

Improved cultural practices can play an important role in augmenting yield of corn crop. For an optimal yield, the nitrogen supply must be available according to the needs of the plant. On the other hand, suitable plants spacing for optimum leaf growth by controlling water, fertilizer and chemical inputs is essential for improving the growth variables responsible for high yield. Optimum plant densities ensure the plants to grow in their aerial and underground parts through different utilization of solar radiation and nutrients. When the plant density exceeds an optimum level, competition among plants for light above ground or for nutrients below the ground become severe, consequently the plant growth slows down and the grain yield decreases (Hasanuzzaman et al., 2009). Plant population is an improtant factor which affects the crop yield. Yield was increased by 4% with increasing plant density (Shapiro and Wortmann, 2006). Higher plant population produce 25% more grain yield and 38% more biomass as compared with low plant population and early sown crop produce 19% more grain yield and 11% more biomass than late planted crop (Abdul et al., 2007).

Maximum crop production can be achieved by development of improved crop hybrids and suitable growing environment and soil with optimum plant population/ha. Optimum plant population is the prerequisite for obtaining maximum yield (Trenton et al., 2006 and Gustavo et al., 2006).

Hybrids exhibited such variations in their yield attributes as cob length (cm), number of row/cob, number of kernels/row, number of kernels/cob, 100- kernel weight (g), stover yield Mg/ha., grain yield Mg/ha, biological yield ton/ha., and harvest index (%), and protein %. However, plant population 64000 plant/ha., gave the highest mean values for most studied characters and protein %. , and reduced weeds spread. Also, hybrid “TWC 352” recorded the highest values of most studied parameters under Alexandria conditions (Kandil, 2014).

Nitrogen is a key factor for plant photosynthesis, ecosystem productivity and leaf respiration (Johnson, 2001 and Martin et al., 2008). Nitrogen stress may affect the light use efficiency and consequently influence long-term changes in vegetation biomass and carbon sequestration (Peng et al., 2012). Increase nitrogen fertilization levels upto 200 kg ha^-1 enhanced the plant height, grain yield and straw yield of hybrid maize, whereas increasing nitrogen levels decreased the harvest, grain, and straw ratio (Dawadi and Sah, 2012). The lowest ear weight was related to the lowest nitrogen level, while the highest ear weight was observed by the highest nitrogen level (240 kg N ha^-1), while there was no significant difference among nitrogen levels was observed on harvest index (Hoshang, 2012). Nitrogen fertilization levels, maize hybrids and their interactions showed such significant effects on maize growth, crop yield and its components. The maximum plant height, leaf area index (LAI), chlorophyll SPAD unit, number of rows/cob , number of kernels/row, number of kernels cob, 1000 grain weight, stover, grain, biological yields, harvest index and protein content were produced by the application either 429 or 357 kg N/ha (Kandil, 2013). There were gradual and significant increases in all growth parameters and grain yield resulted from foliar spray by raising N- fertilizer upto 288 kg N/ha., in both seasons. The S.C Pioneer 30K09 maize hybrid treated with 288 N/ha., produced the maximum values of plant height and grain yield in both seasons (Faheed et al., 2016).

Keeping in view the importance of plant density and nitrogen fertilization, the study was conducted to find out optimum plant spacing and suitable nitrogen fertilization level for getting higher yield of maize hybrid.

MATERIALS AND METHODS

The present study was carried out at the Experimental Farm, Faculty of Agriculture (Saba- Basha), Alexandria University, Egypt, during the two successive growth summer seasons of 2014 and 2015, to study the response of two maize hybrids to spatial distribution and nitrogen fertilization rates in a split- split plot design. Whereas, three factors can be illustrated as follows: the main plot included two maize hybrids (30N11 and 31G98), while plant spacing (20, 30 and 40 cm) was arranged in the sub plots, while nitrogen fertilization (192, 288 and 384 kg N/ha.) allocated in sub- sub plot.

The grains of the tested two hybrids (31G98 and 30N11) were obtained from Maize Research Section Agriculture Research Center, Ministry of Agriculture. The grains were sown on May 8^th and 10^th 2014 and 2015 seasons, respectively.

Soil texture was clay loam. A surface sample (0-30 cm) was collected before planting to identify some physical and chemical properties of this soil, as shown inTable (1) according to Page et al. (1982) and Klute (1986). The preceding crop was Egyptian clover (berseem) in the first season and barley (Hordium vulgare, L.) in the second season, respectively.

Each sub sub plot size was 12.60 m² included 6 ridges each 3 m in length and 0.70 m in width with the distance between hills as the above treatments mentioned.

Phosphorus fertilizer was added at rate of 100 kg calcium super phosphate (15.5% P₂O₅) just before sowing.  Mineral nitrogen fertilizer was fully given the dose in a form of urea (46% N) after thinning before the first irrigation and before the second irrigation.

Table (1).Some Physical and chemical properties of the experimental soil in 2014 and 2015 seasons.

Grain yield and yield components as cob length (cm), number of rows cob^-1, number of kernels row^-1, number of kernels cob^-1,100- kernel weight (g), stover yield ton ha^-1, grain yield ton ha^-1, biological yield (ton ha^-1) harvest index (H.I.%) are measurements were obtained as an average of 2 ridges from mid of each plot.

Protein percentage was determined by estimating the total nitrogen in the grains and multiplied by 6.25 to obtain the percentage according of grains protein percentage to A.O. A.C. (1990). NPK percentages were determined in the dry grains. Their dry weights were determined following drying in a drying chamber to a constant weight at 75^oC for 72 hour according to Tandon (1995). After dryness, the plant samples were milled and stored for analysis as reported. However, 0.5 g of the grains powder was wet-digested with H₂SO₄–H₂O₂ mixture according to (Lowther, 1980) and the following determinations were carried out in the digested solution to determine NPK. Total nitrogen was determined in digested plant material colorimetrically by Nessler`s method (Chapman and Pratt, 1978). Phosphorus was determined by the Vanadomolyate yellow method as given by Jackson (1973) and the intensity of colour developed was read in spectrophotometer at 405 nm. Potassium was determined according to the method described by method Jackson (1973) using Beckman Flame photometer.

Data obtained was exposed to the proper method of statistical analysis of variance as described by Gomez and Gomez (1984). The treatments means were compared using the least significant differences (L.S.D.) test at 5% level probability by using the split- split model as obtained by CoStat 6.311(2005) as statistical program.

RESULTS AND DISCUSSIONS

Results recorded in Tables (2 and 3) revealed that plant height (cm), ear weight (g), grain weight/ear (g), number of grains/ear, 100-grains weight (g), number of rows/ear, grain yield (t/ha), biological yield (ton/ha) and harvest index (%) of two maize hybrids were, significantly, affected by plant spacing and nitrogen fertilizer rates in both seasons.

Results presented in the same tables demonstrated that maize hybrid “30N11” had higher value for the yield and its components i.e. plant height (cm), ear weight (g), grain weight/ear (g), number of grains /ear, 100- grains weight (g), number of rows/ear, grain yield (t/ha), biological yield (ton/ha) and harvest index (%) than the other hybrid “31G98” in the first and second seasons, respectively. The difference may be attributed to genetically differences between two maize hybrids which play an important role for make up the available nutrients and yield for the maize hybrids. These findings are in harmony with those obtained by Kandil (2014).

Results, also demonstrated that spacing between hills (40 cm), significantly, increased the yield and its components than narrower spacing (20 cm). These results are in agreement with those reported by Ahmad et al. (2010), Saadat et al. (2010), Peykarestan and Seif (2012), Moosavi et al. (2012), Lyocks et al. (2013) and Kandil (2014) who showed that there was a significant difference among plants spacing on maize characters.

On the other side, results presented in Tables (2 and 3) revealed that increasing nitrogen fertilizer level up to 384 kg/ha., significantly, increased plant height (cm), and yield components of maize i.e. ear weight (g), grain weight/ear (g), number of grains /ear, 100- grains weight (g), number of rows/ear, grain yield (t/ha), biological yield (t/ha) and harvest index (%) than application of 192 kg N/ha. It can be noticed generally that grain yield and its components affected by nitrogen fertilizer which play an important role in plant growth and finally appeard in gigher grain yield for two hybrids of maize. These finding were consistent with those obtained by Kumar(2008), Khan et al. (2012), Moraditochaec et al. (2012), Nemati and Sharifi (2012) and Kandil (2013).

The interaction between maize hybrids and plant and plant spacing reveal that the highest mean values of straw, and biological yield and harvest index were obtained with 30N11 hybrid at 40 cm. In the contrast, growing 31G98 at 20 cm produced the lowest ones during two cropping seasons (Table 4).                         

With regard to maize hybrids x nitrogen level interaction, results in Table (5) showed that the maize hybrid “30N11hybrid” with 288 kg N/ha., recoded the highest mean value of grain yield in the second season.

Considering interaction among maize hybrids x spacing x nitrogen fertilization level were significant for yield and its components characters in both seasons as cleared in Table (6). However, results revealed that wider spacing of “30N11” hybrid plants at (40 cm) and fertilized with 384 kg N/ha., produced the highest mean value of grain and straw and biological yield in the two respective seasons.

Table (2). Plant height, yield and its components as affected by two maize hybrids, plant spacing and nitrogen

                 fertilizer rates in 2014 and 2015 seasons.

Means at the same column followed by the same letter are significantly different according to L.S.D. at 0.05 value, ns: not significant and *: significant difference at 0.05 level of probability.

Table (3). Yield and its components as affected by two maize hybrids, plant spacing and nitrogen fertilizer rates in 2014 and 2015 seasons.

Means at the same column followed by the same letter are statistically significantly different to L.S.D. at 0.05 value, ns: not significant and *: significant difference at 0.05 level of probability.