Response of Fodder Maize to Various Levels of Nitrogen and Phosphorus

Nitrogen (N) and Phosphorus (P) are of the most important and complex nutrients for the crop plants in particular for grain yield and quality. The field trials were laid out in randomized complete block design having three replications. Research trial plots were located at Agricultural Research Farm of Agricultural University Peshawar (Ameer Mohammad Khan Campus Mardan) during kharif season in 2012 to investigate the response of maize variety (Jalal) to three phosphorus rates (60, 90 and 120 kg∙ha−1) and four nitrogen rates (90, 120, 150, 180 kg∙ha−1) for agronomical traits. These traits investigated included number of plant per m2 (NP m2), plant height (PH), number of leaves plant−1 (NLP), leaf area plant−1∙cm2 (LAP), fresh weight of plants kg∙ha−1 (FW) and dry weight of plant kg∙ha−1 (DW), were investigated. Results of the study showed that application of N @ 180 and P @ 120 kg∙ha−1 significantly increased fodder yield of maize. The linear increase in biomass yield clearly indicated that N was a limiting nutrient factor and that N demand along with P has a positive response. At higher application rates, N fertilizer significantly increased biomass component, improved N uptake with increasing nitrogen use efficiency and decreased its losses to the environment and below plant zone. So this study showed that the phosphorus and nitrogen Corresponding author.


Introduction
Maize (Zea mays L.) is grown as dual purposes such as food, feed, and fodder crop in Pakistan.It plays important roles in both human diet animal feed and provides a large amount of energy and protein [1] [2].It is most important constituent of cattle fodder and poultry feed [3].In Pakistan, maize is the third important crop after wheat and rice.In the year 2010-2011, total area under maize crop in Pakistan was 974.3 thousand hectares with 3706.9 thousand tons of total production [4].The main producers are India, Pakistan, Brazil, France, and Italy.Although the soil and climatic conditions of Pakistan are favorable for the maize production, but its per ha −1 fodder yield is very low as compared to other country of the world.Low yield of maize was due to many factors, but fertilizer application is considered one of the main factors which can increase fodder production on per unit area basis.
Nitrogen is a primary nutrient required by crop plants for their growth and development.Nitrogen plays a key role in vegetative growth and grain production of maize plant [5] [6].The application of nitrogen not only affects the forage yield of maize, but also improves its quality especially its protein contents [7].It is reported that application of nitrogen to maize increase fodder nutritive value by increasing crude protein and by reducing ash and fiber contents [8].Plant height, stem diameter, green fodder yield, protein, fiber, and total ash content were increased by increasing nitrogen levels.Phosphorus is also considered an essential nutrient to plant growth and development.It is an integral part of nucleic acid and is essential for cellular respiration and for metabolic activity.Therefore, the use of phosphorus along with nitrogen will help increase yield of maize [9].Previous studies suggested that phosphorus influenced both maize's forage yield and quality [10].Phosphorus application increased fodder yield and quality by increasing plant height, and the number of leaves plant −1 [11].The objective of this study was to determine the effectiveness of different phosphorus and nitrogen fertilizer on the fodder yield.

Materials and Methods
The field study was conducted at the Agricultural Research farm of Amir Mohammad khan Campus Mardan, the University of Agricultural Peshawar, Pakistan 2012.The experiment was laid out in randomized complete block design having three replications.The soil was ploughed with cultivator 2 to 3 times followed by planking.Four different levels of N (90, 120, 150 and 180 kg•ha −1 ) and three levels of P (60, 90 and 120 kg•ha −1 ) were applied to each experimental unit.Maize variety "Jalal" was sown by broadcast method at the 1st week of July 2012.The net plot size was 4 × 3 m 2 used.Standard cultural practices for maize production were followed during growing season.Data recorded included on the number of plants m 2 , plant height (cm), number of leaves plant −1 , leaf area plant −1 (cm 2 ), fresh weight of plants kg•ha −1 , dry weight of plants kg•ha −1 .

Statistical Analysis
The replicated means were subjected to ANOVA using MS excel (2007).The least significant difference (LSD) was founded by using p < 0.05 that shows the results were significantly different.

Plant Density (Number of Plants m 2 )
Number of plant m 2 is presented in Table 1.Nitrogen levels had significantly increased the number of plant m 2 while the effect of phosphorus on number of plants m 2 not significant.Planed mean comparison showed that control vs rest (fertilized plots) was also found significant for the number of plant m 2 .Interaction between nitrogen and phosphorus levels was found not significant.Mean value of the data indicated that higher number of plants m 2 (21) was observed when nitrogen was applied at the rate of 180 kg N ha −1 followed by 150 kg N ha −1  (19) whereas plots where fertilized at rate of 90 kg N ha −1 resulted in lower number of plants m 2 (17).Control plots resulted in lowest number of pants m 2 (12).

Plant Height (cm)
Data regarding to plant height is presented in Table 2.The plant height was influenced significantly by different levels of nitrogen.Significant increase in plant height was observed by higher nitrogen levels.While the effect of phosphorus was found not significant.Mean comparison showed that control vs rest was also significant for plant height of maize.Interaction between nitrogen and phosphorus levels was found not significant.Mean value of the data indicated that higher plant height (120.6 cm) was recorded when nitrogen was applied at the rate of 180 kg N ha −1 followed by 150 kg N ha −1 with plant height (119.6 cm) and 120 kg N ha −1 with plant height (114.7 cm).Nitrogen at 90 kg•ha −1 resulted lowest plant height (78.3 cm).Plant height was lower in control (79.7 cm) as compared to the rest (108.3 cm).

Number of Leaves Plant −1
Data containing number of leaves plant −1 are presented in Table 3. Nitrogen and phosphorus levels increased affected number of leaves plant −1 .Mean comparison showed that control vs rest was found significant for number of leaves plant −1 of maize.In addition interaction between nitrogen and phosphorus levels was also found significant.Mean value of the data indicated that higher number of leaves plant −1 (12) was recorded when nitrogen was applied at the rate of 180 kg•ha −1 followed by 150 kg N ha −1 with number of leaves plant −1 (11) and 120 kg N ha −1 with number of leaves plant −1 (10).Nitrogen at 90 kg•ha −1 resulted lower number of leaves plant −1 (8).While in case of phosphorus the higher number of leaves plant −1 (11) was recorded when phosphorus was applied at the rate of 120 kg P ha −1 followed by 90 kg P ha −1 with number of leaves plant −1 (10).Where 60 kg P ha −1 resulted lower number of leaves plant −1 (9).Interaction between nitrogen and phosphorus showed that application of P at rate of 120 kg P ha −1 increased no of leaves along with N at 180 kg N ha −1 .Control vs rest indicated that number of leaves plant −1 (10.6) was higher in rest of the plots as compared to control (9).

Leaf Area Plant
Data concerning leaf area is presented in Table 4.The leaf area was positively influenced by different levels of nitrogen but, the effect of phosphorus was found non-significant for the leaf area of maize.Interaction between nitrogen and phosphorus levels was also not significant.Mean comparison showed that control vs. rest was found significant for leaf area of maize plant.Mean value of the data indicated that higher leaf area (348 cm 2 ) was recorded when nitrogen was applied at the rate of 180 kg•ha −1 followed by 150 kg•ha −1 with leaf area (309 cm 2 ) and 120 kg•ha −1 with leaf area (290 cm 2 ).Where the 90 kg•ha −1 resulted in lower leaf area (242 cm 2 ).Control vs rest indicated that leaf area of plants was higher (297 cm 2 ) in rest of the treatment as compared to control (202 cm 2 ).

Fresh Fodder Yield (kg•ha −1 )
Data pertaining fresh weight of plants (kg•ha −1 ) is presented in Table 5. Nitrogen and phosphorus levels were       found significant on fresh weight of plants.Interaction between nitrogen and phosphorus levels was also found significant.Mean comparison showed that control vs rest was significant for fresh weight of maize plants.Mean value of the data indicated that higher fresh weight (2375.9kg•ha −1 ) was recorded when nitrogen was applied at the rate of 180 kg N ha −1 followed by 150 kg N ha −1 with fresh weight (1771.3kg•ha −1 ) and 120 kg N ha −1 with fresh weight (1490.7 kg•ha −1 where 90 kg N ha −1 resulted in lowest fresh weight (1101.9kg•ha −1 ).While in case of phosphorus the higher fresh weight (1764.6 kg•ha −1 ) was recorded when phosphorus was applied at the rate of 120 kg P ha −1 followed by 90 kg P ha −1 with fresh weight (1668.8kg•ha −1 ).Phosphorus at −1 resulted lowest fresh weight (1621.5 kg•ha −1 ).Interaction between N and P showed that application of P at the rate of 120 kg P ha −1 increased fresh weight (2447 kg•ha −1 ) along with N at 180 kg N ha −1 .Control vs rest indicates that fresh weight (888.9 kg•ha −1 ) was lower in control compare to the rest (1685 kg•ha −1 ).

Dry Fodder Yield (kg•ha −1 )
Data regarding dry weight of plants (kg•ha −1 ) is presented in Table 6.Nitrogen and phosphorus levels were significant on dry weight of plants.Interaction between nitrogen and phosphorus levels were also significant.Mean comparison showed that control vs rest was significant for dry weight of maize plants.Mean value of the data indicated that higher dry weight (952.8 kg•ha −1 ) was recorded when nitrogen was applied at the rate of 180 kg N ha −1 followed by 150 kg N ha −1 with dry weight (727.8 kg•ha −1 ) and 120 kg N ha −1 with dry weight (684.3 kg•ha −1 ).While lower nitrogen rate (90 kg•ha −1 ) resulted lowest dry weight (538.9 kg•ha −1 ).For phosphorus the highest dry weight (827.1 kg•ha −1 ) was recorded when phosphorus was applied at the rate of 120 kg P ha −1 followed by 90 kg P ha −1 with dry weight (720.1 kg•ha −1 ).Phosphorus 60 kg•ha −1 resulted lowest dry weight (630.6 kg•ha −1 ).Interaction between N and P showed that application of P at rate of 120 kg P ha −1 increased dry weight (1444.4kg•ha −1 ) along with N at 180 kg N ha −1 .Control plots resulted lowest dry weight (519.4 kg•ha −1 ) as compared to rest of the plots (725.9 kg•ha −1 ).

Discussion
The effect of nitrogen levels was found significant for number of plant m 2 while the effect of phosphorus on number of plants m 2 was found non-significant.Interaction between nitrogen and phosphorus levels was found not significant.Plant density exerts a strong influence on maize growth, because of its competitive effect both on the vegetative and reproductive development [12] [13].
The effect of nitrogen levels was found significant on plant height while phosphorus was found not significant.Interaction between nitrogen and phosphorus levels was also found not significant.It is reported that high plant population results in enhancing plant height [14].Plant competition to light is the main reason for higher plants at dense populations [15].It is reported that plant density and planting pattern did not affect corn height [16].Higher plant densities reduced leaves number per plant by enhancing interplant competition [17].
Effect of nitrogen and phosphorus levels was found significant on number of leaves plant −1 .Also, it's concluded that nitrogen increase leaf length, number of leaves plant −1 [18] [19].
Nitrogen levels had significantly affected leaf area of maize plant and the effect of phosphorus was found not significant.The probable reason of our result might be that N increase vegetative growth while P brings maturity in plant.These are in confirmation with those of [20] [21] who reported that leaf area increased with increase nitrogen and phosphorus levels.The effects of nitrogen and phosphorus levels were found significant on fresh weight of plants.Interaction between nitrogen and phosphorus levels was also found significant.The probable reason might be that N, and P enhanced the vegetative growth of maize plant.Our result is same with previous studies who reported fresh fodder yield increased with increase in nitrogen level [11] [21] [22].
The effect of nitrogen and phosphorus levels was found significant on dry weight of plants.Interaction between nitrogen and phosphorus levels was also found significant.The probable reason of our result might be that N and P increase number of leaves, plant height, leaf area, and vegetative growth due to which dry weight also increased.Our results are in confirmation with those of the previous studies [1] [11] [22] who reported that dry fodder yield increased with increase in phosphorus and nitrogen levels.

Conclusion
The fertilizer treatments significantly affected the yield and quality parameters tested in the present study.The increase in fodder yield with fertilizer application may be due to the greater plant height, the higher stem diameter, the higher number of leaves plant −1 and the higher leaf area plant −1 .Thus, it can be concluded that the maize grown for fodder purpose and the optimum and economical dose of fertilizer for fodder crop of maize cultivar in agroecological condition of Mardan is 180 -120 kg N-P ha −1 .

Table 1 .
Effect of different levels of nitrogen and phosphorus on number of plants m 2 .

Table 2 .
Effect of different levels of nitrogen and phosphorus on plant height (cm).

Table 3 .
Effect of different levels of nitrogen and phosphorus on number of leaves plant −1 .

Table 4 .
Effect of different levels of nitrogen and phosphorus on leaf area plant −1 (cm 2 ).

Table 5 .
Effect of different levels of nitrogen and phosphorus on fresh fodder yield of maize.

Table 6 .
Effect of different levels of nitrogen and phosphorus on dry fodder yield of maize.