Effect of seed rate, phosphorus and nitrogen fertilization on forage yield, leaf to stem ratio and protein content of maize (Zea mays L.

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1 Sudanese Journal of Agricultural Sciences (2014) 1, Effect of seed rate, phosphorus and nitrogen fertilization on forage yield, leaf to stem ratio and protein content of maize (Zea mays L.) EL Tom EL Sadig Ali a *, Sakina Awad Gasim a, Hani Ahmed Eltelib b a Department of Agronomy, Faculty of Agriculture, University of Khartoum, Shambat 13314, Sudan. b Faculty of Agriculture, Alzaiem Alazhari University, Khartoum North 13311, Sudan. Abstract A field experiment was conducted for two consecutive seasons at the Demonstration Farm of the Faculty of Agriculture, University of Khartoum, Shambat, Sudan to study the effect of seed rate, phosphorous and nitrogen on leaf to stem ratio, forage yield and protein content of forage maize. The nitrogen levels were 0, 50, 100 kg N/ha in the form of urea and the phosphorous levels were 0, 100 kg P 2 O 5 /ha in the form of triple superphosphate. The seed rates were 71, 107 and 143 kg/ha. The treatments were arranged in split-split plot design replicated four times. The nitrogen was put in the main plot, phosphorous in the sub-plot and the seed rate in the sub-sub-plot. Increase in seed rate significantly decreased leaf to stem ratio and increased forage fresh and dry matter yield. Crude protein significantly decreased with the increase in seed rate. The effect of phosphorous on all measured parameters was not significant. Nitrogen fertilization significantly increased leaf to stem ratio and forage fresh and dry matter yield. Crude protein in leaves and stems increased significantly with the increase of nitrogen. Introduction Maize ( Zea mays L.) is a member of the family Poaceae originated in Mexico where its oldest known ears were found about 7000 years ago (Mangeldsdorf et al., 1964). The crop has a wide range of uses viz; human food, industrial processed food, production of starch and as forage to feed animals. About 60% of the global harvest of maize is fed to livestock (Dowsell et al., 1996). * Corresponding Author. Tel.: address: tomsadig@yahoo.com In the Sudan, the major grass forage crops include Abu Sabein (Sorghum bicolor), Sudangrass (Sorghum sudanense), (Sorghum bicolor Sorghum sudanense) hybrids and recently maize (Zea mays) (Khair, 1992). Abu Sabein and Sudangrass are grown during summer from March to October but maize can be grown in winter. This solves the problem of livestock feed shortage during winter. Moreover, forage is scarce in natural rangelands during this dry period. Maize also had higher organic matter digestibility and metabolizable energy yield and lower crude fibre percentage than Abu Sabein (Khair et al., 2007). 92

2 Till recently, fodder maize received little attention by researchers in Sudan. Little work has been done regarding plant density, which is important factor in combination with fertilizer application. High seed rates used for production is important since economical yield in forages comes mainly from the vegetative parts. Fertilizer application and establishment of appropriate plant density are the principal factors that form the basis of the forage yield. An adequate supply of nutrients such as nitrogen and phosphorous at each stage is essential for optimum growth and development. In Sudan, a positive response of maize as forage to inorganic nitrogen fertilizers has been reported by Eltelib et al. (2006). Koul (1997) reported an increase in forage yield with increase in seed rate. However, there is no evidence for optimum plant density at which the crop should be raised for forage production as well as the optimum amount of nitrogen and phosphorous fertilizers to be applied. The objective of this study is to investigate the effect of different levels of seed rate, nitrogen and phosphorous fertilizers on yield, leaf to stem ratio and protein content of forage maize. Materials and methods A field experiment was carried out during two consecutive seasons at the Demonstration Farm of the Faculty of Agriculture, University of Khartoum, Shambat, Sudan. The latitude of the area is 15 40'N, longitude is 32 32'E and altitude 360 m above the sea level. The climate is described as semi-arid with only three months of rainfall (July, August and September). The soil is described as deep cracking moderatealkaline clays with ph ranging between The soil was ploughed, harrowed, leveled then ridged to 70 cm. The experiment was laid out in split split-plot design divided into four blocks. Each block divided into three equal units as main-plot. Each mainplot was divided into two units as sub-plots and each sub-plot divided into three units as sub-sub-plot. The size of the sub-sub-plot was 5 3 m 2. Treatments were three levels of nitrogen, two levels of phosphorous and three seed rates. In the main plot three levels of nitrogen; 0, 50, 100 kg N/ha, designated as N0, N1 and N2, respectively. In the sub-plot two levels of phosphorous were assigned namely, 0, 100 kg P 2 O 5 /ha designated as P0 and P1, respectively. In the subsub-plot 3 levels of seed rates of 71, 107 and 143 kg/ha designated as S1, S2 and S3, respectively, were tried. The seeds of an open pollinated maize cultivar (Giza 2) were sown in rows in the eastern side of the ridge in the first week of November for the two seasons. Nitrogen fertilizer in form of urea (46% N) was applied before the third irrigation. Phosphorous was applied before sowing in the form of triple superphosphate (45% P 2 O 5 ). The crop was irrigated seven times in each season at an interval of 10 to 12 days. Weeding was practiced once three weeks from sowing. Data collection Leaf to stem ratio Five plants were cut randomly from the inner rows. Leaves were stripped from the stem. Both leaves and stem were air dried and then weighed to determine the dry weight. The leaf to stem ratio was calculated by dividing the dry weight of leaves by the dry weight of stems. 93

3 Forage yield (ton/ha) At the end of each experiment, plants were harvested at the milky stage; plants in the middle ridge of one meter length were cut at the soil surface and weighed to get the green forage (fresh yield). The same sample used for fresh forage yield was air dried until a constant weight was reached and then weighed to obtain forage dry matter yield. The fresh and dry matter yields were calculated per unit area. Protein content Ten plants were randomly selected from the harvested plants in each plot, their leaves stripped from the stems and both leaves and stems were oven dried and ground using an electric grinder. Sub-samples from the ground samples were subjected to chemical analysis to determine protein content in leaves and stems using the micro-kjeldahl method (AOAC, 1990). Statistical analysis Data of each season were analyzed as split-split plot design by standard analysis of variance techniques (Gomez and Gomez, 1984). Treatments means were separated using the least significant difference (LSD) procedure. Results and discussion Forage yield Increase in seed rate resulted in an increase in forage fresh and dry matter yield (Table 1). This may be due to the fact that high seed rate resulted in high plant density. This result indicated a close relationship between forage yield and seed rate or plant density. Similar results were reported by Yilmaz et al. (2007) and Budakli Carpici et al. (2010). The results obtained revealed that increasing nitrogen level increased forage fresh and dry yield (Table 1). This is attributed to the fact that nitrogen increases the photosynthetic capacity of plant, which enhances growth. This result is in conformity with the findings of other researchers (Eltelib et al., 2006; Budakli Carpici et al. 2010; Hassan et al., 2010). The nitrogen seed rate interaction for forage fresh yield was significant in both seasons. At higher seed rates, the rate of increase in forage fresh yield was higher than that under lower seed rate during the second season (Fig. 1). Higher forage yield was obtained at higher seed rate under high nitrogen levels. This result indicated that at different seed rates the response to nitrogen is different. Phosphorous fertilization had no effect on fresh and dry yield. Similar result was reported by Eltelib et al. (2006). This response might be due to soil factors affecting phosphorus availability, such as phosphorus fixation by the heavy clay soil in which the experiment was conducted or that the experimental alkaline soil has high fixing capacity for the applied phosphorous in the top layer which reduced the availability of phosphorous to the plant. Yang and Jacobsen (1990) observed that when phosphorus fertilizer was added to soil with ph of 8.5, phosphorus quickly reacts to form less soluble compounds with calcium and possibly magnesium. Leaf to stem ratio The results showed a reduction in leaf to stem ratio with the increase of seed rate (Table 2). This may be due to the increase in number of stems compared to leaves at higher seed rates as reported by Oktem and Oktem (2005) and Budakli Carpici et al. (2010). The 94

4 Table 1 The effect of nitrogen, phosphorous fertilization and seed rate on forage fresh and dry matter yield of maize at harvest during first and second seasons Forage fresh yield (ton/ha) Dry matter yield (ton/ha) Treatments Nitrogen levels N0 N1 N c b a c b a c 7.40 b 8.19 a c 7.62 b 9.52 a 0.79 Phosphorous levels P0 P a a a a 7.09 a 7.09 a 7.14 a 7.24 a Seed rates S1 S2 S b a a b a a b 7.31 a 7.31 a b 7.62 a 7.50 a 0.60 Means within columns, in each treatment, followed by the same letter (s) are not significantly different at probability level of 0.05 using least significant difference (LSD) test. : Not significant leaf to stem ratio increased with the increase of nitrogen dose (Table 2). This increase in leaf to stem ratio with nitrogen application is probably due to the increase in number of leaves and leaf area under nitrogen treatments as reported by Eltelib et al. (2006) and Hassan et al. (2010). Pho sphorous had no clear effect on leaf to stem ratio (Table 2). This result was expected due to phosphorous fixation as explained earlier. Similar results were reported by Eltelib et al. (2006). Protein content The increase in seed rate resulted in the reduction of crude protein content of leaves and stems (Table 3). This result is in conformity with that reported by Widdicombe and Thelen (2002). However, other workers reported contrary result (Patricio Soto et al., Budakli Carpici et al., 2010). This indicates that the influence of seed rate on protein content is controversial, so more research is needed in this aspect. Crude protein content in leaves and stems significantly increased as nitrogen rates increased. These results coincided with the findings of some workers (Patricio Soto et al., 2004; Budakli Carpici et al., 2010). Nitrogen fertilization seed rate interaction for leaf protein was significant during the second season. The highest value of leaf protein was at the se- 95

5 Fig. 1 Effect of nitrogen levels on forage fresh yield (ton/ha) under different seed rates during the second season Table 2 The effect of nitrogen, phosphorous fertilization and seed rate on leaf to stem ratio of maize at harvest during first and second seasons Treatments Leaf to stem ratio at harvest Nitrogen levels N c 0.66 b N b 0.72 b N a 0.84 a LSD(0.05) Phosphorous levels P a 0.73 a P a 0.74 a Seed Rate S a 0.79 a S b 0.76 a S b 0.67 b Means within columns, in each treatment, followed by the same letter (s) are not significantly different at probability level of 0.05 using least significant difference (LSD) test. : Not significant Fig. 2 Effect of nitrogen fertilization on crude protein under different seed rates during the second season ed rate of 71 kg/ha under higher nitrogen level, while the lowest value was at 143 kg/ha under the control (Fig. 2). This result indicated that leaf protein content responded differently to nitrogen at different seed rates. Marsalis et al. (2009) reported that at the low nitrogen rates, increasing seed rates resulted in reduced crude protein of forage maize. The response of leaf and stem protein to phosphorous and phosphorous nitrogen interaction was not significant during the two seasons. This might be explained by phosphorous unavailability due to fixation. It can be concluded that nitrogen at rate of 100 kg N/ha improved growth, forage yield and quality of forage maize, while phosphorous has no effect on all studied parameters. On the other hand fresh and dry yield of forage maize responded positively to high plant densities with maximum fresh and dry yields at seed rates of 107 to 143 kg/ha. 96

6 Table 3 The effect of nitrogen, phosphorous fertilization and seed rate on leaf and stem protein content (%) of maize at harvest during first and second seasons Treatments N0 N1 N2 P0 P1 LSD S1 S2 S3 Leaf Stem Leaf Stem Nitrogen levels 7.00 c 5.05 b 6.43 c 4.45 a 9.00 b 6.56 ab 8.45 b 6.41 b a 7.85 a 9.70 a 7.18 c Phosphorous levels 8.62 a 6.11 a 8.09 a 5.81 a 8.81 a 6.86 a 8.29 a 5.95 a Seed rates 9.02 a 6.65 a 8.39 a 6.11 a 9.52 b 6.88 a 8.38 a 5.85 a 8.59 b 5.93 b 7.79 b 5.70 a Means within columns, in each treatment, followed by the same letter (s) are not significantly different at probability level of 0.05 using least significant difference (LSD) test. : Not significant References AOAC (1990). Official methods of analysis. Association of Official Analytical Chemists, 15 th Ed., Arlington, Virginia, USA. Budakli Carpici, E., Celik, N., Bayram, G. (2010). Yield and quality of forage maize as influenced by plant density and nitrogen levels. Turkish Journal of Field Crops 15, Dowsell, C.R., Paliwal, R.L., Cantrell, R.P. (1996). Maize in the third world. Westview Press, USA. Eltelib, H.A., Hamad, M.A., Ali, E.E. (2006). The effect of nitrogen and phosphorous fertilization on growth, yield and quality of forage maize ( Zea mays L.). Journal of Agronomy 5, Gomez, K.A., Gomez, A.A. (1984). Statistical procedures for agricultural research, 2 nd ed. John Willy and Sons. Hassan, S.W., Oad, F.C., Tunio, S.D., Gandahi, A.W., Siddiqui, M.H., Oad S.M., Jagirani, A.W. (2010). Impact of nitrogen levels and application methods on 97

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