Abstract: Field experiment was conducted to study the effect of N-type fertilizers on the yielding components of wheat (Triticum aestivm L.), applied at sowing, vegetative and boot stage. Spike population and number of grains per spike had a significant linear increased with increase in fertilizer levels. Grain weight remained unaffected by fertilizer levels. Types of fertilizer (Ammonium sulphate and Ammonium nitrate) had no significant effect on spike population, number of grain and 1000 grain weight. Split dose (50 kg N ha–1) of fertilizer application at sowing and vegetative stage (S1 + S2) or at vegetative and boot stage (S2 + S3) significantly increased number of productive tillers per unit area. Generally 50 kg N ha–1 applied at boot stage increased grain weight, while number of grains per spike showed no response to split application at any growth stage.
Introduction
Proper amount and time of fertilizer application is considered a key to the bumper crop. Nitrogen is considered a major element of the fertilizer for a good yield. Nitrogen is closely linked to control the vegetative growth of plant and hence determine the fate of reproductive cycle. Researchers argue that grain yield, grain weight and spikes per unit area reduced (Kelley, 1993) and lodging (Mazurek et al., 1992; Ayoub et al., 1994) LAI, dry matter production (Das et al., 1993; Ragheb et al., 1993; Geleto et al., 1995) and disease severity (Ugalde et al., 1993) increases with higher level of Nitrogen. While many found increased number of spike, grain weight (Ragheb et al., 1993; Geleto et al., 1995) and grain yield (Singh et al., 1992; Ragheb et al., 1993; Verma et al., 1993; Geleto et al., 1995) with increase level of N fertilizer. Time of fertilizer application can affect the N-utilization efficiency by cereals (Ragheb et al., 1993). Banziger et al. (1994) stated that photosynthetic capacity of the canopy increased with late N application. Latiri et al. (1992) observed that maximum level of yield components during wet year with 60 kg N ha–1, when applied at tillering and the start of stem elongation. Ayoub et al. (1994) stated that split N application had a little effect on yield, but decreased lodging and spikes population, while grain weight increased. Most of the workers recommended 120 kg N ha–1 for wheat (Lathwal et al., 1992; Verma et al., 1993; Das et al., 1993). The objective of this study was to understand the response of yielding components i,e, productive tillers per unit area, grains per spike and grain weight under various level of N-fertilizers at different growth stages.
Materials and Methods
The experiment was conducted at Malakandher Research Farm, NWFP Agricultural University, Peshawar. Two type of N-fertilizers (ammonium sulphate and ammonium nitrate) and 50, 100 and 150 kg N ha–1 were applied in sole or split dose (50 kg N ha–1 each) at three different stages i.e. sowing, vegetative and boot. Treatments were consisted of control (no nitrogen) and all possible combinations of N levels at various growth stages (Table 1). The experiment was laid out in Randomized Complete Block (RCB) design having four replications with nineteen treatments in each. The plot size was 4 × 2 m, having six rows of 30 cm apart. Wheat cultivar Pirsabak-85 was sown on November 21, 1993.
The number of productive spikes were counted in one meter long row at three different points in each plot and average number of spikes per square meter was calculated. The number of grains per spike was calculated by counting the number of grains of ten randomly selected spikes from each plot. The total number of grains from selected spikes was divided by 10, to get average number of grains per spike. Grain weight was recorded by weighing 1000 grains from each treatment. The data collected were analyzed statistically according to the appropriate design. F-test was used to detect the significance of treatments effect and the LSD was applied for means comparison. ANOVA was further split to understand and compare the means in detail, for which contrasts were done.
Results
All the fertilizer levels significantly produced more spikes per unit area than non fertilized treatments (Table 2). The number of spikes m–2 linearly increased with increase in fertilizer level. The highest number of spikes per unit area was produced by the highest level of 150 kg N ha–1. Different types (ammonium sulphate and ammonium nitrate) showed non significant effect on spike population. Application time of N-fertilizer had a significant effect on number of spikes. When 50 kg N ha–1 was applied at sowing and vegetative stage, their effect on spike population was significant. At vegetative stage, fertilizer application significantly increased the number of spikes compared to application of fertilizer at sowing. While same dose of fertilizer at sowing or boot stage had the same effect on spike population. A 100 kg N ha–1 in a split dose at S1 + S2 produced significantly more number of spikes per unit area than applied at S1 + S3. Control plots produced significantly less grains per spike compared to fertilized plots (Table 3). On average, fertilized plots produced 45 grains per spike as compared to 38 grains per spike from control plots.
| Table 1: | Details of the experimental treatments |
| AS = Ammonium sulphate AN = Ammonium nitrate | |
| Table 2: | Number of spikes per square meter as affected by type, level and application time of N-fertilizers |
AS = Ammonium sulphate AN = Ammonium nitrateS1 = At sowing S2 = Vegetative stage S3 = Boot stage $ = contrasts followed by * are significant at the 0.05 level of probability, others are not significant. | |
| Table 3: | Number of grains per spike as affected by type, level and application time of N-fertilizers |
AS = Ammonium sulphate AN = Ammonium nitrate S1 = At sowingS2 = Vegetative stage S3 = Boot stage $ = contrasts followed by * are significant at the 0.05 level of probability, others are not significant. | |
| Table 4: | Grain weight (g) of wheat as affected by type, level and application time of N-fertilizers |
AS = Ammonium sulphate AN = Ammonium nitrateS1 = At sowing S2 = Vegetative stage S3 = Boot stage $ = contrasts followed by * are significant at the 0.05 level of probability, others are not significant. | |
Fertilizer levels had a significant linear effect on grains per spike. The highest number of 51 grains per spike were recorded from the highest level of 150 kg N ha–1. Type of fertilizers and their application time had no significant effect on grains production. Type of fertilizers and their various levels did not affect the grain weight (Table 4). Among the application time, nitrogen fertilizer at boot stage significantly increased the grain weight. Application of 50 kg N ha–1 at boot stage (S3) produced significantly heavier 1000 grain of 44.1 g compared to 41.5 g from S1 treatment.
Discussion
Spikes per unit area is one of the important yield component. Geleto et al. (1995) stated that grain yield is closely related to the number of spikes per unit area. The combined effect of N-fertilizer levels, type and application time showed differences for spike population. Fertilized plots produced more spikes than non-fertilized plots. Such response can be attributed to the adequate nitrogen availability which might facilitate the tillering ability of the plants, resulting in greater spike population. Ayoub et al. (1994) and Verma et al. (1993) reported that spike population increased with increase in nitrogen level. The application of N-fertilizer at vegetative stage increased number of spike per unit area. It is concluded that N-fertilizer at vegetative stage could be the proper time, which provided supporting base for spike formation. Number of grains per spike is the productive efficiency of any cereal crop. Latiri et al. (1992) concluded that grain yield was best correlated with the number of grains per unit area. Fertilizer levels showed a significant linear response for number of grains per spike. Number of grains significantly increased with the increase in fertilizer level. This can be justified with a logic that nitrogen availability satisfied the plant requirement for growth and development, which enable the plants to produced more number of grains per spikes. Greater number of grains per spike from increased N-fertilizer rate was also obtained by Geleto et al. (1995) and Ayoub et al. (1994). Grain weight is highly correlated with photosynthate accumulation. It contributes significantly to the final grain yield. Single dose of 50 kg N ha–1 at boot stage significantly increased the grain weight as compared to its application at sowing. This can be attributed to the availability of nutrients at the grains formation stage, which might have enhanced the photosynthetic ability and its accumulation in the grains, resulted in greater weight. Banziger et al. (1994) observed greater photosynthetic capacity of the canopy by late N-application. Early application of N may be utilized in the formation of vegetative parts. Ayoub et al. (1994) also favored split application of N, which increased 1000 grain weight.