Cotton Response to Split Application of Nitrogen Fertilizer
To investigate the effect of split application of nitrogen on cotton yield and its components for medium stapled commercial cotton (Gossypium hirsutum L.) variety MNH554, a field trial was carried out at Cotton Research Station, Multan during 1998 to 2000. Ten nitrogen levels viz., 0, 56, 84, 112, 112, 140, 168, 168, 196 and 224 kg N ha-1 were tested in Randomized Complete Block Design having three replications. Nitrogen was applied in split doses at planting. Ist irrigation, flowering and boll fermentation. 56 kg P2O2 ha-1 was also applied as a basal dose . N168 kg ha-1 proved superior over others when split applied in three equal doses i.e., 56, 56, 56 kg N ha-1 at Ist irrigation, flowering and boll formation stages. This produced a significant increase in plant height, bolls per plant, boll weight and seed cotton yield. On the average of three years 168 kg N ha-1 gave 212.8% increase in seed cotton yield over O.N.
The role of cotton in improving and stabilising the economy of Pakistan is the most fundamental. For achieving sustainable growth rate in cotton production there can be two strategies namely horizontal and vertical. Pakistan is working on both but due to limitation of area for cotton, increase in yield per hectare become the most crucial. Factors responsible for raising cotton production include high potential varieties, accretion in irrigation facilities, augmenting fertilizer application, improving cultural practices, judicious plant protection and incentive prices. (Abdullah, 1972; Ali, 1972).
Fertilizer application plays an important role in raising cotton production. Nitrogen is utilized in cotton plant to greater extend and is generally considered the most important nutrient for maximizing the cotton yield (Breitenbeck and Boquet, 1993). An adequate supply of nitrogen is essential for well developed growth, fruiting and yield of cotton crop (Boquet et al., 1994; Choudhry and Sarwar, 1999). It is widely recognized that nitrogen supply exerts a marked influence on the vegetative and reproductive growth. In recent years there has been tendency among some cotton growers to increase maximum yield potentials by applying higher amount than that recommended nitrogen rates. Increasing rate of nitrogen increased plant height and the number of flowers and bolls, but do not increase seed cotton yields because of increased shedding of lower bolls. Moreover, they added that excessive nitrogen fertilizer does not improve the yield potential or profitability of cotton production (Boquet et al., 1994; Latif et al., 1994; Khan et al., 1994; Soomro et al., 1997). It is also important to minimize the potential contamination of ground water with nitrate from excessive use of fertilizer on light textured soils. The maturity of the cotton crop, as evidenced by first and second picking was found to be dependent on the N rate (Mascsagni et al., 1993). Fertilization is now a system problem and research has to quantify the relationship between all the factors of fertilization and create modles in order to help farmers to manage their crops (Bisson et al., 1994). It has been advocated that recovery of applied nitrogen is very low when crop is grown under irrigation (Soomro and Waring, 1987; Soomro et al., 1990).
Khan et al. (1993), Arain et al. (2001), Memon et al. (2001) and Soomro et al. (2001) reported a significant increase in pant height, boll weight, bolls per plant and seed cotton yield with split application of nitrogen fertilizer. The applied nitrogen may be lost from the soil plant system through leaching and denitrification resulting in yield reductions (Wayne, 1986). Keeping this fact in view, the study was undertaken to determine the effect of split application of nitrogen on seed cotton yield and its components.
Materials and Methods
The studies were undertaken at Cotton Research Station, Multan during 1998
to 2000 MNH554 a medium stapled variety of Tetra ploid cotton (Gossypium
hirsutum L). The experiment was conducted in randomized complete block design
having three replications eith a plot size of 13.6 m X 3m. The crop was sown
on 30.5.1998, 30.5.1999 and 1.6.2000 on a well prepared seed bed in 75cm apart
rows with a single row cotton drill, 57 kg P h-1 was applied as basal
dose in all treatments except T1 During 2000 cotton crop followed
cotton on a soil having pH 8.1, rich in potash, low in organic matter, total
nitrogen and available phosphorus. The crop was grown under field conditions
with normal husbandry practices regarding thinning, interculture, irrigation
and plant protection etc. The nitrogen was applied in the form of urea according
to the following schedule. The dose of urea applied at sowing, according to
the treatment programme was well mixed in soil to prevent evaporation of the
nitrogen in sunlight, while the other doses were given with irrigation water.
Plant height, bolls per plan, boll weight were recorded on ten consecutive
plant selected in the central row of each plot. The plant height was recorded
from ground level to the top of the main axis on normally growing plants. The
bolls on each selected plant were counted, picked and weighed for bolls and
bolls weight. The seed cotton was hand picked and weighed for plot yields. The
plot yields were converted to seed cotton kg ha-1.
Results and Discussion
The data were subjected to statistical analysis to discover the optimum N dose and time of application and the results are presented in the following para graphs. The data on means are given in Table 1 and analysis of variance (mean squares) in Table 2.
Plant height (cm): The plant height data (Table 1)
reveals that on the basis of three years averages the maximum plant height (151.5cm)
was obtained in T10 (224 kg N ha-1, as 56, 56, 56, 56). The lowest
figure was 106.4cm given by T1 (0 kg N ha-1) . On annual basis ,
the data reveal that the maximum Plant height observed during 1998, 1999 and
2000 was under T10 (224 kg N ha-1), T9 (196 kg N ha-1)
and T10 (224 kg N ha-1) respectively. Year to year variation in plant
height was noticed but the height trend in relation to treatments remained unchanged.
In addition to the total quantity of N, the time of application of N doses seems
more decisive for controlling plant height.
The difference among the treatments were highly significant . It is obvious from the results that the height increases with the increase in the amount of nitrogen. Moreover the distribution of nitrogen and application at different growth stages is also very important as it markedly affected the plant height. The results are in conformity with Khan et al. (1993; 1994) and Soomro et al. (1997).
Bolls per plants: The data on bolls per plant (Table 1) indicate that increased N dose had direct impact on boll bearing capacity of MNH554. Bolls per plant significantly increase by increasing N. On the average of three years data, the highest bolls per plant (35.5) were recorded by T8 (168 kg N ha-1), followed by 32.0 bolls obtained by 168 kg N ha-1 (T7), whereas the lowest figure was 11.6 given by 0 kg N ha-1 (T1). On annual basis maximum bolls per plant i.e., 38.3, 37.3 and 31.0 respectively during 1998, 1999 and 2000 were recorded on plants having N application, 168 kg ha-1 (T8), the lowest bolls per plant were from 0 kg N ha-1 The results are highly significant for treatments. It is clear from the data that the gradual increase in bolls per plant was recorded from T1 to T8. Similar results have been reported by Khan et al. (1993), Arain et al. (2001) and Soomro et al. (2001).
Boll weight (g): The results (Table 1) reveal a positive response of boll weight to the amount of nitrogen added, however, time of application of N dose did not show any marked variation in boll weight. The three years average data show that the maximum boll of 3.6 gm was obtained by 168 kg N ha-1 (T8), closely followed by 3.5 g produced by 196, 168, 140 and 112 kg N ha-1 (T9, T7, T6, T5). The boll weight was minimum (2.8 g) under 0 kg N ha-1 (T1). On annual basis, the data present comparable results. The differences among the treatments were highly significant (Table 2). The findings are in line with Khan et al. (1993), Arain et al. (2001) and Soomro et al. (2001).
Seed Cotton yield (kg ha-1): The yield data (Table
1) reveal a positive response to increased doses of N from 0 to 168 kg N
ha-1. The highest yield of seed cotton, on the basis of three years-combined
averages was 3090.3 kg ha-1 picked from T8, crop received 168 kg
N ha-1 applied in three equal doses of 56 kg ha-1 at Ist
irrigation, flowering and boll formation stages. It was closely followed by
T7 (2911.7 kg ha-1), whereas T1 (0 kg N ha-1) generated
lowest seed cotton yield of 988 kg ha-1.
|| Means of data on Cotton response to split application of
nitrogen fertilizer, at Cotton Research Station, Multan 1998 to 2000
|| Cotton response to split application of nitrogen fertilizer
The seed cotton yield was decreased with increased application of N i.e., 196
and 224 kg N ha-1. 168 kg N ha-1 (T8) increased seed cotton
yield 212.8% over control (0 kg N ha-1). It seems logical that due
to split application some of the N was available to the plant during their most
active growth period particularly from Ist. Irrigation onward. Same types of
results have been obtained by Boquet et al. (1994), Choudhry and Sarwar
(1999), Khan et al. (1993), Arain et al. (2001), Memon et al.
(2001) and Soomro et al. (2001).
Highly significant differences in yield performance were manifested from year
to year but the trend, as evident from the mean data on year basis, remained
almost the same. It signifies that MNH554 is adequately stable concerning its
genetic potential for yield of seed cotton. The differences due to treatments
were highly significant (Table 2). On yearly basis maximum
seed cotton yield of 3345.0, 3448.0 and 2478.0 kg ha-1 respectively
during 1998, 1999 and 2000 were recorded having N application (T8, 168 kg N
ha-1). The lowest seed cotton yield was obtained in T1 (0 kg N ha-1)
during 1998, 1999 and 2000 having 1007.7, 1215.7 and 740.7 kg ha-1
respectively . The similar results have been reported by Khan et al.
(1993) Arain et al. (2001), Memon et al. (2001) and Soomro et
al. (2001). The increase in seed cotton yield caused by yield caused by
increasing N rate may be due to more bolls per plant and better boll weight.
It can thus be concluded that with out supplementing with nitrogen fertilizer,
better yield can not be obtained, for maximum yield potential of MNH554 168
kg ha-1 in split doses will be sufficient.
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