RESPONSE OF MAIZE TO NITROGEN APPLICATION METHODS AND ROW CONFIGURATION

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1 Sarhad J. Agric. Vol.29, No.3, 213 RESPONSE OF MAIZE TO NITROGEN APPLICATION METHODS AND ROW CONFIGURATION MAHMOOD UL HASSAN 1 *, RIAZ AHMAD 1, EHSAN ULLAH 1 and MUHAMMAD SAQIB 2 1. Department of Agronomy, University of Agriculture, Faisalabad - Pakistan 2. Institute of Soil & Environmental Sciences, University of Agriculture, Faisalabad-Pakistan *Correspondence author: muh.agr@gmail.com ABSTRACT A field study was conducted on sandy clay loam soil to evaluate the impact of row spacing and N application method on the productivity of maize (Zea mays L.). The experiment was conducted using four row spacings (6 cm spaced single rows, 9 cm spaced double row strips, 9 cm spaced single rows and 135 cm spaced double row strips) and two methods of nitrogen (N) application (broadcast and band placement) using hybrid (Monsanto DK-922) during 26 and 27. The experimental design was a randomized complete block design with a split plot arrangement and four replications. Row spacing was allotted to main plots and N application method to sub plots. The plant population of maize was kept uniform (55555 plants ha -1 ) for all the treatments. The results revealed that sowing maize at 9 cm spaced double row strips was superior to other spacings with respect to leaf area index, total dry matter, crop growth rate, plant height, number of grains ear -1, 1-grain weight and grain yield. The increase in maize grain yield was 7.35 to and 9.39 to 21.98% in 26 and 27, respectively. Band placement of N produced 1.94 and 11.61% higher grain yield than broadcast N application. We conclude that sowing maize in 9 cm double row strips and applying N as band placement could improve growth and grain yield. Keywords: Zea mays L., row spacing, nitrogen, band placement, grain yield. Citation: Hassan, U.M., R. Ahmad, E. Ullah and M. Saqib Response of maize to nitrogen application methods and row configuration. Sarhad J. Agric 29(3): INTRODUCTION Maize (Zea mays L.) is third leading cereal crop of the world after wheat and rice. It is extensively grown in temperate, subtropical and tropical regions of the world. Maize grain is a key industrial raw material for diverse purposes. Besides nutritive food, it is also a good source of high quality edible oil. Maize grain is also being increasingly used in animal and poultry feed and grown as a fodder crop for silage (Witt and Pasuquin, 27). Maize important for countries like Pakistan, where a rapidly escalating population of 185 million has by now out stripped the available food supplies. In Pakistan, it occupies an important place in the existing cropping systems. In , it was planted on an estimated area of 185 thousand hectares with a total annual production of 4631 thousand tones in Pakistan (GOP, 213). The average grain yield of maize (4268 kg ha -1 ) is not only substantially lower than the production potential of existing genotypes, but is also lower than other maize growing countries like France (8979 kg ha 1 ), U.S.A. (8924 kg ha 1 ), Canada (7819 kg ha 1 ) and China (4854 kg ha 1 ) (Anonymous 23). Yield potential of a crop is not only dependent upon its genetic makeup but also the environment in which it is grown. The genetic potential, can be exploited by providing a favorable growth environment. Thus, maize responds differently to varying environments (Javed et al., 26) under various agromanagement practices due to its high yielding potential. Row spacing or planting pattern is of prime importance in maize production. It is imperative that maize crop should be planted by using a method that ensures efficient uptake of nutrients and minimum mutual over-shading and interplant competition. The lack of basic information about production technology and ever escalating price of chemical fertilizers are major constraints for growing high yield maize in Pakistan (Farhad et al., 29). Nitrogen (N) fertilization is a key component to high corn grain yield and optimum economic return. It is a constituent of all proteins and enzymes in plant metabolism and integral part of chlorophyll (Brady, 199). Most agricultural soils are deficient in nitrogen for growth of crops, and this deficiency is overcome by the judicious use of N fertilizers. Urea is a major form of N used in the world. However, the efficiency of using urea-n for crops is a major concern due to its losses like runoff, erosion, leaching, and gaseous emission. Side dressing or band placement of nitrogenous fertilizer is an efficient method for N utilization and bio-chemical transformation and it uses moisture more efficiently than broadcast method (Lehrsch et al., 2). The present study was conducted to compare effects of different row spacings and N application methods on growth and yield characteristics of hybrid maize.

2 Mahmood ul Hassan, et al. Response of maize to nitrogen application methods 34 MATERIALS AND METHODS The study was carried out on a sandy clay loam soil at the Agronomic Research Area, University of Agriculture, Faisalabad, Pakistan during 26 and 27. Experimental site is located at 31.3 o N latitude, 73.6 o E longitude and 184 m altitude. Meteorological data for both years were collected from the meteorological observatory of the Department of Crop Physiology, University of Agriculture, Faisalabad, Pakistan (Table 1). Table 1. Metrological data during growing season 26 and 27 Temperature (C o ) Maximum Minimum Average R.H (%) Total Rainfall (mm) MONTH July August September October November Physio-chemical analysis of soil at the site was done before sowing. Composite soil samples were collected from the experimental area at a depth of 15-3 cm (Table 2). Table 2. Physio-chemical analyses of the soil samples from Experimental Site. DETERMINATION A. Physical characteristics Sand (%) Silt (%) Clay (%) Textural class Sandy clay loam Sandy clay loam B. Chemical analysis ph EC (dsm -1 ) Organic matter (%).69.7 Total N (%) Available P (ppm) Available K (ppm) The experiment was laid out in randomized complete block design (RCBD) with a split plot arrangement and four replications. Row spacing was assigned to main plots and N application method to sub plots. The row spacing treatments were 6 cm spaced single rows, 9 cm spaced double row strips, 9 cm spaced single rows, and 135 cm spaced double row strips. Nitrogen application methods were broadcast and band placement. The smallest experimental unit (sub plot) was 3.6 m x 7.6 m. Maize single cross hybrid Monsanto DK-922 was sown on 5 th and 11 th of July in 26 and 27, respectively. A dibbler was used for sowing of crop seeds on a well prepared seed bed in patterns as per treatments, using a seeding rate of 3 kg ha -1. The NPK fertilizers were applied at kg ha -1 in the form of urea, DAP (diammonium phosphate), and SOP (sulphate of potash), respectively. A full dose of phosphorus and potassium were applied at the time of sowing. Nitrogen was applied in two equal applications, first at sowing and second when maize height was approximately 6 cm. The amount of phosphorous was calculated from DAP fertilizer alongwith the nitrogen available from DAP source as it contains 18% N. The remaining nitrogen was supplemented from urea (46% N). During the crop growing period, seven irrigations were applied in both years as and when needed. Thinning was carried out at the fourleaf stage of the crop and same plant population (55555 plants ha -1 ) was maintained for all treatments. Standard plant protection measures were adopted, including 2 kg ha -1 before the first irrigation to control insect pests particularly maize borer Chilo partellus (Swinhoe.) and shootfly Atherigona soccata (Rond.). Two hoeings were carried out to keep the crop free of weeds before earthing up, which was done after the 3 rd irrigation to avoid lodging. Maize was harvested at physiological maturity, as indicated by the appearance of a black abscission layer at the base of grains (about 3-35% grain moisture content) on 18 th and 29 th of November 26 and 27, respectively. After harvest, crop plants were sundried and then tied into small bundles. Afterwards, ears were separated from the stalk and further sundried for a few days before shelling which was done at 14% seed moisture content. Measurement of leaf area index, total dry matter (TDM), crop growth rate (CGR), plant height, number of grains ear -1, 1-grain weight, grain yield and harvest index were recorded during the course of study. To determine the leaf area, sampling was initiated 3 DAS (days after sowing) and at regular intervals of fifteen days until 15

3 Sarhad J. Agric. Vol.29, No.3, DAS. Leaf area was measured by a portable leaf area meter (Model CI-22) and total leaf area was calculated by selecting ten plants randomly from each experimental unit and then averaged. Thereafter, leaf area index (LAI) was calculated by the Watson (1947) formula given as: Leaf Area LAI = Land Area Total dry matter was recorded at 15-day intervals by randomly selecting ten plants from each experimental unit. Sampling was initiated 3 DAS and terminated at 15 DAS. Each sample was weighed to determine the fresh weight and then chopped into small pieces. A 1-gram sub-sample from each experimental unit was taken in muslin cloth bags, oven dried at 75 ± 5 o C to a constant dry weight and then dry weight per plant was calculated. The crop growth rate (CGR) was calculated by the formula of Hunt (1978). W W 1 CGR = (g m -2 day -1 ) Where, T 2 T 1 = 15 days T T 1 Plant height was calculated by selecting ten plants at random from each experimental unit at maturity, their height was measured using a meter rod from ground surface to the top of plant and measurement were averaged for each sub plot. Grains from ten randomly selected ears of each treatment were shelled, counted and converted into number of grains ear -1. Thousand-grain weight was determined from three randomly selected samples of 1 grains from each experimental unit, weighed on an electric balance, and then averaged. Grain yield was determined after sun drying the ears for 15 days, shelling was done with mechanical maize sheller. Grain yield of each plot was recorded and converted into tons per hectare (t ha -1 ). Harvest index was determined as the ratio of grain yield to biological yield. Data were analyzed using Fisher s analysis of variance in the computer statistical package MSTAT-C (Freed and Eisensmith, 1986) and treatment means were compared using least significant difference (LSD) test at 5% level of probability (Steel et al., 1997). RESULTS AND DISCUSSION Leaf Area Index (LAI) It is a dimensionless variable and was first defined as the total one-sided area of photosynthetic tissue per unit ground surface area (Watson, 1947) which expresses the photosynthetic potential of a crop at its particular growth stage. LAI in all treatments increased progressively with the advancement of crop growth period, reached maximum at 75 DAS, and then declined at 9 DAS during both years of study (Fig. 1). The LAI was higher (6.18 and 6.14) in both years when the crop was planted at 9 cm spaced double row strips, but it was closely followed by 135 cm spaced double row strips (5.96 and 5.76). However, the lowest values for LAI were recorded in plots of 9 cm spaced single rows (5.53 and 5.4). The higher leaf area index in 9 cm spaced double row strips was probably due to better interception of light by the crop. These results are in line with the findings of Ahmad et al. (21) who reported an increase in leaf area index by planting maize in narrow rows. Maddoni et al. (26) also reported similar results by concluding that narrow rows exhibited larger LAI than wider rows due to improved light interception by crop in narrow rows particularly around silking and postsilking stage. Similarly, the LAI was significantly increased with the band placement of N (6.14 and 5.87) over broadcast method in both the years. The positive effect of band placement of N on leaf area index could be attributed to increased nitrogen supply, which might have promoted synthesis of new leaves led to higher LAI (Chatterjee, 21).These results are supported by the findings of Ahmad et al. (22) and Hassan et al. (21) who stated that in maize more LAI was produced with band placement of nitrogen application than broadcast method. A positive and linear relationship was observed between grain yield and leaf area index with regression value of.972 and.951 in 26 and 27, respectively, which clearly indicated that the increase in grain yield was in accordance with the increase in leaf area index (Fig. 3). Total Dry Matter (TDM) There was increase in TDM of maize with the progress in crop growth period during each year of study (Fig. 2). Maize grown at 9 cm spaced double row strips exhibited higher TDM (1655 and 159 gm -2 ) than other row arrangements compared with lowest in 9 cm spaced single rows (1283 and 1152 gm -2 ) (Table 3). Higher TDM in 9 cm double row spacing over others was might be due to more solar radiation interception by crop plants and efficient utilization of available resources which led to better crop growth. Cox et al. (26) pointed out that narrow or wide rows did not affect the dry matter accumulation in maize significantly, although the narrow row corn intercepts more photosynthetically active radiation than wider rows. Band placement of N

4 Mahmood ul Hassan, et al. Response of maize to nitrogen application methods LAI S1 S2 S3 S4 LAI N N LAI S1 S2 S3 S4 LAI N N Fig. 1. Periodic leaf area index of maize under various row spacing and method of nitrogen application during 26 and 27.

5 Sarhad J. Agric. Vol.29, No.3, TDM S 1 S 2 S 3 S 4 TDM N 1 N TDM S 1 S 2 S 3 S 4 TDM N 1 6 N Fig. 2. Periodic total dry matter accumulation as influenced by row spacing and method of nitrogen application during 26 and 27.

6 Mahmood ul Hassan, et al. Response of maize to nitrogen application methods 344. resulted in a maximum TDM of 164 and 1428 gm -2 whereas broadcasting resulted in 133 and 122 gm -2 during 26 and 27 respectively. Higher TDM in band placement of nitrogen was probably due to more LAI and crop growth during the growing period, as there was better nitrogen supply to plants. The interaction between row configuration and N application method was not significant for TDM. There was a positive and linear correlation between grain yield and TDM, with regression values of.976 and.977 (Fig. 4). The regression lines indicated the increase in TDM with corresponding increase in grain yield. Crop Growth Rate (CGR) It is a measure of growth rate of plant per unit land area and time. CGR of maize varied significantly by row configuration and N application method during 26 and 27 (Table 3). In 26, the highest CGR was recorded in crop planted at 9 cm spaced double row strips with a mean value of gm -2 day -1 whereas the lowest in 9 cm spaced single rows, the CGR was gm -2 day -1. The same trend was exhibited during 27 and CGR was varied on an average from gm -2 day -1 to gm -2 day -1. These results are in accordance with the findings of Ahmad et al. (21) who found a significant increase of 16-18% in CGR of maize when row spacing was reduced from wider to narrow. However, Maddoni et al. (26) showed that row spacing did not affect the CGR of maize. Band application of nitrogen to maize significantly increased the CGR over broadcast method in both the years (23.5 and 2.7 gm -2 day -1 ). This increase was likely due to less nitrogen losses in the field because of its greater exposure to crop plants, hence more availability near to the plant roots as compared to broadcast method. Crop growth rate depends on the amount of intercepted photosynthetically active radiation (PAR), hence the leaf area index plays an important role in dry matter production (Girardin & Tollenaar, 1994). They further concluded that changes in row spacing can affect crop canopy size and architecture, factors often associated with photosynthetic efficiency and plant growth. These results are in conformity with those reported by Hassan et al. (21) and Ahmad et al. (22). The interactive effect of row spacing and nitrogen application method on CGR was significant during 26 and non-significant in 27. There was a positive and linear correlation between grain yield and CGR of maize crop with regression value of.962 and.994, showing the interdependence between these two parameters (Fig. 5). Plant Height (cm) There was significant variation among various row spacing with regard to plant height of maize during each year of study (Table 3). In 26, maize planted at 9 cm spaced double row strips produced taller plants (235.5 cm) and it was closely followed by cm for 135 cm spaced double row strips. The lowest plant height was recorded for 9 cm spaced single rows (21.13 cm), which was at par with 6 cm spaced single rows ( cm). A similar trend was observed during 27. Higher plant height associated with maize grown at 9 cm spaced double row strips was probably due to better growing conditions. The research conducted by Shafi et al. (211) concluded that plant height was increased by 6% when maize row spacing was narrowed from 75cm to 45cm. Band placement of nitrogen in maize was superior as it produced significantly taller plants with mean values of and cm during 26 and 27, respectively compared with and 21.93cm in broadcast method, respectively. Higher plant height achieved in maize with band placement of nitrogen was due to better availability of N and its uptake which ultimately accelerated the dry matter accumulation and crop growth rate of the crop plants throughout the growing period. Number of Grains Ear -1 The row arrangements, method of N application, and their interaction had significant effects on number of grains ear -1 of maize during both years (Table 3). In 26, the crop planted at 9 cm spaced double row strips in combination with band placement of nitrogen application (S 2 x N 2 ) produced maximum number of grains ear -1 (41.1) which was at par with 135 cm spaced double row strips + band placement (393.5) and 6 cm spaced single rows + band placement of nitrogen (383.9). The lowest number of grains ear -1 (319.3) was recorded in maize grown at 9 cm spaced single rows with broadcast N application. A similar trend was observed during 27. More grains ear -1 in treatment S 2 x N 2 was attributed to suitable space available to the crop plants for better interception of sunlight to increase the photosynthetic activities and better chance of fertilization during the tasseling silking period of the crop. Similarly, band placement of nitrogen fertilizer near to plant roots make it readily available to the crop plants and also its better utilization over broadcast method. These results are in agreement with the findings of Shafi et al. (211) and Shah et al. (21) who reported significant variation in number of grains ear -1 under different row spacing and found it maximum at 75 cm row spacing. Ahmad et al. (22) also concluded that significantly more grains ear -1 were recorded in maize with N fertilizer be applied as band placement against the minimum in broadcast method. But these results are at odds with those of Ahmad et al. (21) who suggested that narrowing row spacing had a suppressive influence on the number of grains ear -1 so that it decreased by 7 and 1.5% when row spacing was decreased from 75 to 6 and 45 cm. There was a

7 Sarhad J. Agric. Vol.29, No.3, Fig. 3: Relationship between leaf area index (gm -2 day -1 ) and grain yield at varying row spacing. Fig. 4: Relationship between total dry matter (g m -2 ) and grain yield at varying row spacing. Fig. 5. Relationship between crop growth rate (gm -2 day -1 ) and grain yield at varying row spacing. Fig. 6. Relationship between number of grain ear -1 and grain yield at varying row spacing. Fig. 7. Relationship between 1- grain weight (g) and grain yield at varying row spacing. Fig. 8. Relationship between harvest index and grain yield at varying row spacing.

8 Mahmood ul Hassan, et al. Response of maize to nitrogen application methods 346 Leaf area index Total dry matter ( g m -2 ) Crop growth rate (gm -2 day -1 ) Plant height (cm) Number of grains ear -1 1-grain weight (g) Grain yield (t ha -1 ) Harvest index (%) TREATMENTS A: Planting pattern (S) S 1 : 6 cm spaced b 2.8 b b single rows ab bc bc bc bc ab bc bc bc bc bc S 2 : 9 cm spaced a 6.14 a 1655 a 159 a a a a a double row strips a a a a a a S 3 : 9 cm spaced b 5.4 c 1283 c 1152 c c c 33. c 33.4 c single rows c b c c c c S 4 : 135 cm spaced a 21.5 b 362. b double row strips ab b ab ab ab a ab b ab b ab LSD (P.5) * * B: Nitrogen application method (N) N 1 : Broadcast b 133 b 122 b b b b b b b b b b b b b b N 2 : Band a 5.87 a 164 a 1428 a 23.5 a 2.7 a a a placement a a a a a a a a LSD (P.5) C: Interaction (S x N) S 1 x N d c S 1 x N b ab 37.1 cd b S 2 x N b b b S 2 x N a a a S 3 x N e c 294. d S 3 x N c c c S 4 x N S 4 x N cd 24. ab c c ab 379. a LSD (P.5) Means followed by different letters in columns are significantly different at P.5

9 Sarhad J. Agric. Vol.29, No.3, positive linear relationship between grain yield and the number of grains ear -1 having regression values of.927 and.966 in both the years of study (Fig. 6). 1-Grains Weight (g) The grain weight is one of the major yield contributing factors, which reflects the photosynthetic potential of a crop plant and its capacity to transport assimilates into economically valuable plant organs (Rizwan et al., 23). Row arrangements and method of N application significantly affected 1-grain weight of maize but their interactive effect was non-significant (Table 3). Maize planted at 9 cm spaced double row strips exhibited significantly higher test weight of and g as against the lowest of and g in case of 9 cm spaced single rows in both the years under study. The reason for heavier grains in 9 cm double row strip planting pattern could be due to more uniform plant spatial distribution which increased light interception coupled with uniform supply of moisture and nutrients enabled the crop plants to produce more photosynthates which ultimately led to higher dry matter accumulation to accelerate net assimilation rate. Similar observations were reported by Shafi et al. (211) and Shah et al. (21), who found an increase in 1-grain weight by narrowing row spacing from 9 to 75 cm. Conversely, the band placement of nitrogen to maize was found to be significantly better with regard to 1-grain weight in both the years having corresponding mean values of and g over the minimum in broadcast method and g during 26 and 27, respectively. Increase in 1-grain weight in band placement of nitrogen was due to better physiological response of crop to enhance plant growth due to more availability and uptake of nitrogen around the grain filling period of the crop. Similar results were reported by Ahmad et al. (22). The highly significant and positive linear correlation was observed between grain yield and 1-grain weight which reflect the interdependence of two characters with regression value of.998 and.996 (Fig 7). Grain Yield (t ha -1 ) Grain yield per unit area is a function of interaction among various yield contributing factors, which are usually affected differently by the growing conditions and crop management practices. Maize planted in 9 cm spaced double row strips produced significantly more grain yield (6.66 t ha -1 and 5.96 t ha -1 ), which was about 7.35 to and 9.39 to % higher than the other row spacings under study during 26 and 27, respectively. A greater potential for yield enhancement existed with shift of row spacing in maize (Ahmad et al., 21). The increase in grain yield may be therefore related to management and specific growing conditions in the plots planted at 9 cm spaced double row strips than rest of the row spacings. Although, the plant density for each plot was same, so plants had the same amount of space, just distributed differently but in S 2 there was probably better light interception, more nutrients and moisture uptake which contributed more LAI, CGR and yield attributes and resulted into the higher grain yield. Yield response to decreased row spacing was negatively correlated to radiation interception at pollination time with the wider row spacing. Radiation interception was not measured in this study but it is likely that the proportion of incoming radiation intercepted was very high during both years due to excellent crop growth (Shapiro et al., 26). Similar results were reported by Shafi et al. (211), Ahmad et al. (21), Charles (29) and Lehrsch et al. (2) who concluded that narrowing the row spacing exhibited increase in grain yield of maize. Band placement of nitrogen produced a grain yield of 6.49 and 5.6 t ha -1 whereas nitrogen applied broadcast produced 5.78 and 4.95 t ha -1 during 26 and 27, respectively. The increase in grain yield of maize by band placement was probably due to more N uptake and its continuous supply to maize plants near plant roots throughout the growing period and improved all physiological characteristics of the plant that led to better yield attributes and grain yield. The interaction between row spacing and N application method was not significant in both years. These results are in agreement with the findings of Kaiser et al. (25) and Ahmad et al. (22) who found more grain yield of maize with band placement of nitrogen over broadcast. Harvest Index (%) Harvest index is the ability of crop plant to convert dry matter into economic or grain yield. Various row spacings exhibited significantly different harvest index value of maize crop during both years. Maximum harvest index (34.29 and %) was recorded for maize in 9 cm spaced double row strips during both years as against the minimum (32.99 and 33.2 %) in 9 cm spaced single rows, however, the difference could not reach to the level of significance (Table 3). Research conducted by Shapiro et al. (26) and Saif et al. (23) showed similar results. Similarly, more harvest indices with mean values of and % were observed in band placement of nitrogen to maize crop over broadcast method (33.2 and 32.97%) in both years of experimentations. The interactive affect of both the factors including row spacing and nitrogen application method was found to be non-significant. There was a significant and linear relationship between grain yield and harvest index (Fig. 8). Regression values accounted were.975 and.878 in 26 and 27, respectively.

10 Mahmood ul Hassan, et al. Response of maize to nitrogen application methods 348 Economic Analysis The highest net income (Rs and ha -1 ) was recorded in plots planted in 9 cm spaced double row strips compared with other planting patterns during 26 and 27, (Table 4). Band placement of N was produced the highest net income of Rs ha -1 compared with the broadcast method (Rs ha -1 ) during 26. A similar trend was observed in 27. The increase in net income was probably due to higher grain and stover yield and better resource utilization. The interaction between row spacing and N application method was non-significant in both years. Table 4. Net Income (Rs.) of Maize as influenced by varying Row Spacing and Method of Nitrogen Application. TREATMENTS A : Planting pattern (S) S 1 : 6 cm spaced single rows bc bc S 2 : 9 cm spaced double row strips a a S 3 : 9 cm spaced single rows 6997 c 4512 c S 4 : 135 cm spaced double row strips b 5496 ab LSD (P.5) B : Nitrogen application method (N) N 1 : Broadcast b b N 2 : Band placement a a LSD (P.5) C : Interaction (S x N) LSD (P.5) - - Means followed by different letters in columns are significantly different at P.5 CONCLUSIONS AND RECOMMENDATIONS It is concluded from the results that maize hybrids should be sown in 9 cm spaced double row strips alongwith band placement of nitrogen compared to broadcasting for obtaining higher growth, yield and economic return. REFERENCES Ahmad, M., A. Khaliq, R. Ahmad and A.M. Ranjha, 21. Allometery and productivity of autumn planted maize hybrids under narrow row spacing. Int. J. Agric. Biol. 12: Ahmad, R., A. Mahmood, M. Ikraam and B. Hassan. 22. Influence of different irrigation methods and band placement of nitrogen on maize productivity. Int. J. Agric. Biol. 4: Anonymous. 23. Production year book. FAO. 53:79-8. Brady, N.C The nature and properties of soils. 1 th ed. New York: Macmillan Publishing Co., USA. Charles, O.O. 29. Decreased row spacing as an option for increasing maize (Zea mays L.) yield in Trans Nzoia district, Kenya. Plant Breed. Crop Sci. 1(8): Chatterjee, R. 21. Physiological attributes of cabbage (Brassica Oleracea) as influenced by different sources of nutrients under Eastern Himalayan Region. Res. J. Agric. Sci. 1(4): Cox, W.J., J.J. Hanchar, W.A. Knoblauch and J.H. Cherney. 26. Growth, yield, quality and economics of corn silage under different row spacings. Agron. J. 98(2): Farhad, W., M.F. Saleem, M.A. Cheema and H.M. Hammad. 29. Effect of poultry manure level on the productivity of spring maize (Zea mays L.). J. Anim. Plant Sci. 19(3): Freed, R.D., and S.P. Eisensmith MSTAT micro computer programme, Michigan State Uni. Agric. Michigan, Lansing, USA. Girardin, P.H. and M. Tollenaar, Effects of intra-specific interference on maize leaf azimuth. Crop Sci. 34: GOP Economic Survey of Pakistan Finance and Economic Affairs Division, Ministry of Finance, Govt. of Pakistan, Islamabad, Pakistan. Pp.21. Hassan, S.W., F.C. Oad, S. Tunio, A.W. Candahi, M.H. Siddiqui, S.M. Oad, A.W. Jagirani. 21.

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