Pakistan, despite an agricultural country, is deficient in food grains and other food items. The main cause of food shortage in Pakistan has been the failure of production of food grain to keep pace with the linear increase in population. For bridging the gap between demand and supply of food grains, productivity needs to be enhanced. The feasibility to increase per unit yield is more because yield potential of maize crop has not been realized so for, as there is a large gap between potential and actual yield per acre.
Besides other factors, yield is greatly affected by weeds in the field. Weeds being injurious, harmful or poisonous, are a constant source of trouble for the successful growth and development of economic crops. Weeds compete with crops for light, moisture, space and plant nutrients and thus indirectly deprive the crops of nutrients and other environmental requirements and consequently interfere with the normal growth of crops. In NWFP, the yield losses due to weeds are approximately 20-40% (Anonymous, 2001). Weeds pose severe problems for crop husbandry and infest fallow land, reducing the soil fertility and soil moisture and develop a potential threat to the succeeding crops. About two hundred and eighty different types of weeds have been recorded in NWFP with varying infestation status. The most serious weeds that cause damage to the maize crop in NWFP are Echinochloa crus-galli, Leptochloa sp., Cyperus rotundus, Sorghum halepense, Cynodon dactylon, Digiteria sanguinalis, Convolvulus arvensis, Tribulus terrestris, Digera muricata and Portulaca olereacea (Marwat, 1984).
Shad et al. (1993) reported that application of primextra provided excellent weed control in maize. Miller and Libbey (1999) reported that maize yield generally responded positively to increased weed control. Knezevic et al. (1996) reported that grain yield was significantly increased by herbicides treatments in maize. Rout and Satapathy (1996) reported that highest grain yield of maize was obtained from the herbicides treated plots.
In view of the importance of the problem from the national point of view, the research work was conducted to study the impact of different herbicides on different weeds and to know the response of crop to such herbicides in terms of tolerance, yield and yield components.
Materials and Methods
The study was conducted at Malkandher Research Farm, NWFP Agricultural University, Peshawar during kharif 2001. Maize hybrid P 3203 was used in the experiment. The lay out of experiment was in randomized complete block (RCB) design. There were nine treatments in each replication (Table 1) with at plot size of 5 x 3.75 m2.
|| Different treatments used in experiment
Numbers of rows per treatment were five and plant to plant distance and row to row distance was maintained at 25 and 75 cm, respectively.
The data on the following parameters was recorded during the course of experiment: Number of sedges m-2, number of grassy weeds m-2, number of broadleaf weeds m-2, weeds density m-2, weeds biomass (g m-2), phytotoxicity of herbicides on crop, germination percentage of crop, plant height (cm), number of leaves plant-1, leaf area (cm2), number of cobs plant-1, cob length (cm), number of kernels cob-1, 500 kernel weight (g), biological yield of maize (t ha-1), grain yield (t ha-1), harvest index and finally economics of weed control.
Standard procedures were adopted for recording and calculating data on various
parameters of weeds and crop and finally the data recorded were subjected to
statistical analysis and the treatments means were separated by least significance
difference (LSD) test (Steel and Torrie, 1980).
Results and Discussion
Number of sedges m-2: Data indicated that sedges m-2 were significantly (P ≤ 0.05) affected by different herbicides (Table 2). It could be inferred from the data that maximum number (97.67 m-2) of sedges were recorded in the plots treated with stomp and minimum (19.33 m-2) sedges were observed in the plots treated with dual gold followed by primextra, (23.33) and 2,4-D with (47.33 sedges m-2). The best treatments were statistically comparable with the hand weeded check (Table 2). The Cyperus rotundus recorded in stomp treated plots were noted with dried leaves and stunted growth. Similar results were reported by Shad et al. (1993).
Number of grasses m-2: Statistical analysis of the data (Table
2) revealed that number of grasses m-2 were significantly (P
≤ 0.05) affected by different weeds control measures. Mean values of the
data indicated that maximum number of 176.7 grasses m-2 were observed
in the weedy check plots followed by Banvel (183).
||Net Profit from different weed control treatments in maize
While minimum number (10) of grasses m-2 were comparable with the
hand weeded check noted in plots treated with dual gold followed by plots receiving
primextra having 19.67 grassy weeds m-2. It could be inferred from
the results that statistically the results of hand weeded plots, dual gold and
primextra treated plots were at par with each other. The species of grasses
found were Leptochloa sp., Echinochloa crusgalli and Digiteria
sanguinalis. The results are in analogy with those reported by Shad et
al. (1993). They reported that application of metolachlor + atrazine provided
excellent control of Echinochloa sp., Cyperus rotundus and Cynodon
Number of broad leaf weeds m-2: Data indicated that broad
leaf m-2 were non-significantly (P ≤ 0.05) affected by various
weeds control treatments applied in maize crop (Table 2).
However, maximum number of 2.33 broad leaf weeds m-2 were noted in
trifluralin treated plots, whereas zero (no weed) broad leaf weeds m-2
were recorded in plots treated with 2,4D. The data indicates that overall
there was a abundance of grasses in the experiment and the broadleaf were in
small percentage of the overall weed count.
|| Number of sedges m-2, grasses m-2,
broadleaf weeds m-2, weeds density m-2 and weeds biomass
(g m-2) as affected by different treatments
|| Data regarding yield and yield components of maize as affected
by different treatments
|Means in the column followed by different letters are significantly
different at P ≤ 0.05,NS = non significant
However, the control was statistically at par with all other herbicidal applications
except hand weeded, 2,4-D and Dual gold treated plots. The broadleaf weeds found
in the field in density wise were Euphorbia prostrata, Digera muricata, Portulac
aoleracea and Convolvulus arvensis, respectively.
Weed density m-2: Statistical analysis of the data (Table 2) revealed that number of weeds m-2 were significantly (P ≤ 0.05) affected by various herbicides in maize crop. Mean values of the data indicated that maximum weeds (248.7 m-2) were recorded in weedy check plots, while among the herbicidal treatments minimum weeds (30 and 44.67 m-2) were recorded in dual gold and primextra treated plots, respectively. The density of weeds in dual gold and primextra was even statistically at par with the hand weeded check. Weed density was significantly affected by different treatments. After first irrigation Cyperus rotundus and Digiteria sanguinalis were the major weed species. However, after second and third irrigations, the population of Echinochloa crus-gali and Leptochloa sp. dominated all the species throughout the remaining season. There was no increase in the weed population after fourth irrigation. So dual gold indicated good control of grasses as well as broad leaf weeds. The weed density of banvel treated plots (234.3 m-2) was statistically at par with the weedy check. This was attributed to the fact that banvel is broadleaf killer and the majority of weeds found in the experimental field, belonged to grassy nature or sedges. The result is in agreement with Hafeezullah (2000) and Sobotka et al. (1983). They reported that weed control methods significantly affected weed density m-2.
Weeds biomass (g m-2): Statistical analysis of the data presented in Table 2 indicated the weeds biomass harvested from different weed control treatments in maize crop. Analysis of the data revealed that weed biomass was significantly (P ≤ 0.05) affected by various herbicides in maize crop (Table 2). Maximum dry weight of 405.00, 403.33 and 378.33 g were recorded in banvel, weedy control and jinong treated plots, respectively. While minimum (173.33, 198.33 and 223.33 g) weeds biomass were recorded in dual gold, primextra and stomp treated plots, respectively. It was observed that dry weight of weeds m-2 decreased with the application of herbicides and hand weeding. Lower dry weight of 173 g m-2 was obtained from dual gold treated plot and greater dry weights of 403.33 and 378.33 g m-2 was obtained from weedy control and banvel treated plots, respectively. The results were in agreement with Hafeezullah (2000) and Shakoor et al. (1986). They observed that dry matter of weeds from the weedy control plots was significantly greater than the chemically and manually weeded plots.
There was no specific phytotoxicity of herbicides to crop except banvel, which affected the number and growth of cobs. Abnormal terminal leaves of maize plants were recorded in banvel treated plots. Rolling of leaves in a few plants is the similar result reported by Krishnamurthy et al. (1974).
Germination percentage of crop: The results and thoroughly observations showed that germination percentage of the maize, hybrid P-3203 was hundred percent. However, in the plots where density of Cyperus rotundus was in greater numbers, the germination percentage was little affected by delaying the germination of maize seeds.
Plant height (cm) of maize: Statistical analysis of the data (Table 3) revealed that different treatments had a significant (P ≤ 0.05) effect on plant height. Mean values of the data indicated that maximum plant height of 220.33 cm was recorded in hand weeded plots which was statistically at par with dual gold (216 cm) and primextra (213.33 cm). The minimum plant height of 180 cm was measured in weedy check plots which was statistically equal with banvel treated plots with 181.33 cm plant height. The difference in plant height is attributed to the various intensities of weed competition with maize plant. Similar results were obtained by Kamel et al. (1983).
Number of leaves plant-1: Statistical analysis of the data
(Table 3) revealed that number of leaves per plant were significantly
(P ≤ 0.05) affected by different treatments. It could be inferred from the
data that maximum number of (13.4) leaves plant-1 were recorded in
hand weeded plots. These were however, statistically at par with dual gold (13.17)
and stomp (13.10). The minimum (11.10) leaves plant-1 were recorded
in the plots treated with banvel and weedy control, with 11.33 leaves plant-1.
Leaf area (cm2): Leaf area was significantly (P ≤ 0.05) affected by different treatments (Table 3). Maximum leaf area of 7744.00 cm2 was recorded in hand weeded plots which was comparable with plots receiving dual gold with leaf area of 7607.33 cm2 and primextra (7073 cm2). The minimum of 5019.33 cm2 leaf area was computed in weedy control and banvel treated plots with only 5138 cm2 leaf area. As leaf is the basic photosynthetic machinery for plant food, hence its size would directly affect the yield and yield components of crop. The results were in agreement with Akhtar et al. (1984). They observed that manual weed control gave greatest leaf area at tasseling.
Number of cobs plant-1: Non significant differences were obtained for number of cobs per plant due to different treatments (Table 3). In all the treatments, one cob per plant was recorded. However, mean value of a few treatments had less than one cob per plant. The decrease in number of cob per plant was due to excessive number of weeds in the plots. Similar results were reported by Akhtar et al. (1984).
Cob length (cm): Statistical analysis of the data (Table 3) revealed that different treatments had a significant (P ≤ 0.05) effect on cob length. Mean values indicated that maximum cob length of 19.67 cm was recorded in hand weeded plots, while minimum cob length of 13.33 cm was observed in weedy control plots. However it was statistically at par with all other treatments except dual gold and primextra with 18 and 17.33 cm cob length. These results are in conformity with the results of Kamel et al. (1983). They reported that weed control treatments improved cob length.
Number of kernels cob-1: Number of kernels cob-1 was significantly (P ≤ 0.05) affected by different treatments (Table 3). It could be inferred from the data presented that maximum (548) kernels cob-1 were recorded in hand weeded plots. These were however, statistically at par with dual gold (544.67) and primextra (540). The minimum (461) kernels cob-1 were comparable in banvel treated plots with 462 kernels cob-1. Similar results were reported by Kamel et al. (1983).
500 kernels weight: Statistical analysis of the data (Table 3) revealed that 500 kernels weight was significantly (P ≤ 0.05) affected by different treatments (Table 3). Mean value of the data revealed that maximum 500 kernel weight of 121.33 g was recorded in hand weeded plots followed by dual gold treated plots with 119 g 500 kernels weight. The minimum (114 g) 500 kernels weight was recorded in both weedy control plots and plots receiving banvel. These results are in agreement with the results of Janjic et al. (1983).
Biological yield (t ha-1): Higher biological yield of 14.43 t ha-1 was obtained from hand weeded plots (Table 3). However this was comparable with the plots treated with dual gold and primextra with 14.10 and 14.00 t ha-1 biological yield. The lowest (12.50 t ha-1) biological yield was recorded in weedy control plots which was statistically at par with Banvel (12.40 t ha-1). As leaf area, number of leaves per plant, plant height, ear length, diameter and number of grains contribute in increasing the biological yield, the results reported by Kamel et al. (1983) are in analogy with our results.
Grain yield (t ha-1): It could be inferred from the data (Table 3) that maximum (6.13 t ha-1) grain yield was recorded in hand weeded plots which was statistically at par with dual gold (6.00 t ha-1). The minimum (4.47 t ha-1) grain yield was recorded in weedy control plots. However this was comparable with the banvel (4.85 t ha-1). As the number of kernels cob-1, 500 kernels weight and cob length increased significantly by different treatments, the yield was also increased. Janjic et al. (1983) and Knezevic et al. (1996) reported that best grain yield of maize was achieved with application of metolachlor at the rate of 4 kg ha-1.
Harvest index (%): Statistical analysis of the data revealed (Table 3) that harvest index was non significantly affected by different treatments. The maximum of 42.56% harvest index was recorded in hand weeded plots and minimum of 37.93% harvest index in weedy control plots.
Economics of weed control: Net profit of different treated plots were compared and it was recorded that maximum grain yield and biological yield of 6.13 and 14.43 t ha-1 was obtained from hand weeded plots. However due to increasing amount of labour expenses, the net profit was decreased. The results of the experiment showed that maximum net profit of Rs. 42030 per hectare was obtained from plot treated with dual gold followed by primextra (39020) and minimum of Rs. 33050 and 33108 per hectare was obtained from banvel treated plots and weedy control plots (Fig. 1).
In conclusions, hand weeding is the best method for controlling weeds and getting higher yield but shortage of labour and higher costs are great hurdles for adoption this method. Maximum net profit of Rs. 42030 ha-1 was obtained from dual gold treated plots followed by hand weeded and primextra treated plots. Integrated weed control methods may be employed where feasible.