Abstract: Weeds infesting the cotton fields in district Multan did not indicate a uniform pattern. Five weed species were distributed throughout the cotton fields while the rest were observed at specific sites only. The frequent weeds were Cynodon dactylon, Cyperus rotundus, Euphorbia helioscopia, Silene conoidea and Sphenoclea zeylanica which got their representation in all the three surveyed sites of this district. Some weed species were present at specific sites only. Weeds infesting the rice fields in various districts of the Punjab province indicate that in district Sheikhupura common weeds of rice fields were Cynodon dactylon, Cypress rotundus, Echinochloa colonum,
Digera arvensis infestation in maize field
Fimbristylis miliacea, Marsilea minuta, Paspalum distichum and Sphenoclea zeylanica. Some species were present at particular sites only and were not noted at any other site. These species included Cyperus difformis, Cyperus iria, Panicum sp., Parthenium sp. and Salsola foetida at Kala Shah Kaku where Marsilea minuta was totally absent. To record the weed flora in maize fields of Punjab province, three sites each in district Pakpatan and Bahawal Nagar were surveyed. It was noted that in district Pakpatan the maize fields were infested mostly by five weeds namely Cyperus rotundus, Sesbania sp., Cynodon dactylon, Citrullus vulgaris and Sonchus asper which occurred in quite dense stands. The survey of wheat fields in three districts of the Punjab was carried out on the same pattern of selecting three sites per district. It was noted that in district Gujrat seven weed species occurred very frequently and very dense stands were noted for them at majority of the sites surveyed. These species included Anagallis arvensis, Euphorbia helioscopia, Fumaria indica, Daucus sp., Lathyrus aphaca, Lepidium sativum, and Vicia sativa. Some weeds occurred at specific sites and formed a prominent portion of the weed flora at that site such as Poa annua at Gujrat and Rumex dentatus at Wazirabad sites. The soils collected from cotton fields of three districts in Punjab revealed that soil was clay loam in Multan and Rahim Yar Khan Districts. The data for soils collected from rice fields of various sites in the Punjab indicated that in all the three districts Sheikhupura, Gujranwala and Sialkot, the soil was clay loam in texture having average pH round about 8 and field capacity above 60%. Germination percentage from seeds already present in the soil was observed and it was noted that it was higher in Hafizabad and Gujrat districts as compared to district Jhelum.
Problem statement: This project aims at survey of weeds infesting the arable fields in the Punjab and development of effective weed control strategies. Hopefully at the completion of this project, the data generated will prove of great scientific importance. The project is also expected to assist the farming community to improve their earning.
- Survey of weeds infesting the arable fields in the Punjab for determining the main sources of weed infestation and determination of spatio-temporal variation in the weed spectra as well as soil seed banks.
- Development of techniques for judicious weed control mechanism.
- To create awareness among farmers for reducing weed infestation and adopting integrated weed control approach, to reduce the use of herbicides environmental pollution and save endangered biodiversity as well as foreign exchange.
- Farmers’ training and pursuance to adopt effective integrated weed control rather than relying on herbicidal weed control only.
- To save foreign exchange being spent on importing herbicides.
- To reduce environmental pollution, and conserve biodiversity especially pollinators (honeybees and butterflies) and predatory insects threatened by extensive use of pesticides including herbicides.
Methodology: Weed specimens, and soil were collected from almost all the sites surveyed for collecting the data about weed infestation in cotton, rice and wheat fields. Soil samples collected from different sites were analyzed for determining their N, P, K content, organic matter content, field capacity and electrical conductivity was performed following the standard analytical procedures.
Results and Discussion:
i. Weed Infestation in cotton Fields. At Central Cotton Research Institute weeds namely Convolvulus arvensis, Cynodon dactylon, Cyperus rotundus, Ipomoea aquatica and Silene conoidea were found in cotton fields at Bahadur Chowk district Rahim Yar Khan. In district Muzaffar Garh, the cotton fields in the surroundings of Muzaffar Garh city were infested by 12 weed species.
ii. Weed infestation in rice fields.
The survey of rice fields in district Sheikhupura showed overall infestation by nine weed species. The most common weeds at Kala Shah Kaku site were Parthenium sp., Panicum sp., Paspalum disticum, Salsola foetida, Echinochloa colona and Cyperus rotundus occurring at frequencies of 80, 68, 52, 52, 52 and 40% respectively. Cyperus difformis rarely occurred with 20% frequency but it formed most dense strands than all the remaining weeds indicating 35% density in rice fields. Cynodon dactylon, Echinochloa colona and Parthenium sp., were the next three weeds forming dense strands with 12, 11 and 11% density respectively.
In district Gujranwala at Naushehra site, the rice fields were infested with five weed species namely Citrulus vulgaris, Cynodon dactylon, Echinochloa colona, Dactyloctenium aegyptium and Panicum sp. Of these Echinochloa colona and Paspalum disticum were the most frequent ones existing in all the fields while Panicum sp., occurred at about 92% of the sampling sites. As regards the density of weeds at this site Echinochloa colona was the most thickly populated (36%) weed as compared with its counter part weed species. Cynodon dactylon, Citrullus vulgaris and Paspalum disticum were the next densely populated weed species.
The rice fields in district Sialkot were commonly populated by Echinochloa colona, Marsilea minuta, Paspalum disticum, Cyperus difformis and Sphenoclea zeylanica. Out of these weeds Cyperus difformis and Sphenoclea zeylanica formed the densest strands than all the other weeds.
Tribulus terrestris infestation in maize field
iii. Weed infestation in maize fields.
Weeds recorded in the maize fields at Pakpatan site can be arranged in three frequency classes. Cynodon dactylon was common weed and was the only member in group I, at frequency level of 88%. The second group consisted of two occasional weeds namely Citrullus vulgaris and Dactyloctenium aegyptium each having a frequency of 48%. Rarely occurring weeds were included in group III, which comprised of Amaranthus viridis, Chenopodium album, Chenopodium murale, Cyperus rotundus, Polygonum barbatum, Sesbania sp., and Xanthium strumarium. The densest strands were formed by three weed species namely Cynodon dactylon (27%), Dactyloctenium aegyptium (18%) and Cyperus rotundus (17%) followed by Chenopodium murale having a density of 11%. The remaining weeds exiting at this site had density in single digit.
Data relating to weeds infesting the maize fields in Bahawal Nagar district indicated that at Chishtian site, Cyperus rotundus was a common weed present in all the fields. It was followed by frequently observed Cynodon dactylon,while Citrullus vulgaris, and Solanum nigrum and Lepidium sativum were noted occasionally. It was seen that Cyperus rotundus and Lepidium sativum formed better strands than other weeds.
iv. Weed infestation in wheat fields.
In Jhelum the wheat fields were infested by six frequently occurring weed species. Out of these six weeds, comparatively more frequent ones were Medicago denticulata, Asphodelus tenuifolius, Anagallis arvensis and Fumaria indica. The next two weeds having slightly less frequency were Euphorbia helioscopia, Chenopodium album. Regarding the density of plant species, the densest strands were observed for Chenopodium album, Euphorbia helioscopia, Medicago sativa and Anagallis arvensis.
At Bhimber road site in district Gujrat, a comparatively different trend was noted regarding the weeds found in wheat fields. At this site the most frequent weeds were Anagallis arvensis, Daucus sp., Phalaris minor, Avena sativa and Medicago denticulata. Three of these species i. e., Anagallis arvensis, Phalaris minor and Daucus sp., formed notable trends at densities of 29, 28 and 23% respectively while the other two species existed at less dense level.
At Gujrat site the frequently occurring weeds in wheat field were Poa annua, Malva neglecta, Lepidium sativum and Daucus sp., while Phalaris minor and Lathyrus aphaca were observed rarely. At this site the prominent dense strand was formed by Poa annua only. Nevertheless, Lathyrus aphaca (12%), Lepidium sativum (8%), Malva neglecta (6%) and Phalaris minor (3%) existed in low density in wheat fields in Gujrat. At Wazirabad site Phalaris minor was the most common weed and represented itself in all the fields surveyed. The next frequent weed species were Lepidium sativum, Lathyrus aphaca, Melilotus indica and Euphorbia helioscopia. The density of Phalaris minor dominated the fields forming 44% weed population. It was followed by Euphorbia helioscopia, Lathyrus aphaca and Lepidium sativum.
v. Physical and chemical attributes of soil collected from arable fields.
Soil samples collected from cotton fields:
In district Multan, the soil was clay loam having pH value 8 field capacity, 45-56%. ECe value was about 2.5d Sm-1 in two sites while in the third site Uch Sharif it was 3.5 d Sm-1. The amount of organic matter was reasonably high at Central Cotton Research Institute (CCRI) farm and Basti Malook but it was quite low at Uch Sharif site being 4.7 mgg-1 dry soil. The soil in Rahim Yar Khan District was overall clay loam except at Bahadar Chowk where it was sandy clay. The features of soil were almost similar in clay loam soil collected from two sites. In it the pH was about 8, ECe value round about 2 and Field capacity about 55% while the organic matter in this soil was about 3.8 mgg-1 dry soil. The N was 0.11 mgg-1 dry soil and P value was above 11.7 mgg-1 dry soil. The soil of Muzaffar Garh is overall sandy in nature being clay loam at one site (Panjnad). The pH value was about 8, ECe value round about 2 d Sm-1 and field capacity 45%. Being sandy in nature the amount of organic matter and other nutrients was comparatively low in the soil of this district. However the seed stock seems to be quite high in soil of this district as the number of seeds germinated from 100g soil was 145,175 and 221 in the soil of Alipur, Panjnad and Muzaffar Garh sites respectively.
b. Soil samples collected from rice fields:
At all sites of district Sheikhupura the soil is clay loam in texture having pH 8, ECe around 3.5 d Sm-1 and field capacity range from 45-71%. It possesses sufficient organic matter from 8.3 to 9.5 mg/g dry soil. Quantity of N (0.11-0.16 mgg-1 dry soil) appears to be bit low while the other two nutrients p (11.3-12.5 mgg-1 dry soil) and K around 0.08 mgg-1 dry soil seem to be in reasonable amount. Weed seed germination in this soil had a huge variation for various sites. This germination rate was 211/100g soil in Feroze Watoan as against 87 and 55 in soil of Kala Shah Kaku and Jandiala Sher Khan which might be due to the difference of seed stock in the soil.
The soil in district Gujranwala was also clay loam in texture having a pH round about 8 at field capacity range from 65% - 81%. Soil EC value ranged from 1.7-2.5 dSm-1. The amount of organic matter was about 7 mgg-1 dry soil. The amount of N (0.15-0.19, P (11.5-13.7) and K (0.06-0.09) seem to be reasonable for a normal soil. Due to variation in the amount of seed stock in the soil there was a great difference in the germination of the seed/ 100 g soil. This value was nil, 45 and 155 at Eimnabad, Kat Nisar and Naushehra respectively.
Sialkot district being a member of the same belt along with Sheikhupura and Gujranwala the soil characteristics were almost similar to them. The soil was clay loam with pH round about 8 field capacity range 57- 77% and ECe 2.7d Sm-1. The organic matter in this district was comparatively higher than Sheikhupura and Gujranwala being about 9.7 mgg-1 dry soil. The amount of N was also slightly higher in the soil of this district than the other two being about 0.19 mgg-1 dry soil on the average. P ranged from 11.8-12.5 mgg-1 dry soil and K about 0.08 mgg-1 dry soil, which are the features of normal soil. Due to variation in seed stock in the soil, the number of seeds germinated in soil of Marala, Sialkot and Daska sites were 29, 79 and 129 respectively.
c. Soil samples collected from maize fields:
The soil of Pakpatan site is clay loam in texture and has almost all the features normal. Soil pH was 8.1, ECe round about 2 d Sm-1, and the field capacity 63-72 %. The organic matter was between 4.3 and 4.9 mgg-1 dry soil while N was between 0.17-0.20 mgg-1 dry soils which appears to be normal figures for this type of soil. The amount of P ranged from 12.08-14.5 mgg-1 dry soil and is quite reasonable. The amount of K ranged from 0.04-0.06 mgg-1 dry soil. The amount of seed stock present in the soil germinated at the rate of 45, 75 and 85 from 100 g soils of Sugar mill site, Yousaf Wala and Pakpatan sites respectively.
As compared to Pakpatan district, the soil of Bahawal Nagar has sandy in texture possessing a pH of 7.8, ECe range of 1.9-2.4 d Sm-1 and field capacity of 66-77%. The organic matter was relatively low at Bahawal Nagar site being 3.5 mgg-1 dry soils; the amount of N, P, and K was also calculated to be low for the soil of this site. The values of these three nutrients were 0.11, 10.5 and 0.03 mgg-1 dry soil which seem to be low for a good soil. The nutrient (N, P, and K) values for other sites were almost comparatively higher. The number of seeds germinated was 28, 37 and 45 in the soil of Hota More, Bahawal Nagar and Chishtian sites respectively.
Soil samples collected from wheat fields:
The soil from District Jhelum indicate that the soil was sandy loam at Jhelum and Dina sites while it was clay loam at Kharian. The soil had pH about 7.7, field capacity averaged to be 68% while there existed a variation in ECe at the three sites. It was the highest (3.9 d Sm-1) at Jhelum site and lowest (1.5 dSm-1) while it was 2.5 dSm-1 at Kharian. The organic matter was almost similar at the three sites averaging to be 3.7 mg/g dry soil. The amount of P (13.5 mgg-1 dry soil) and K (0.07 mgg-1 dry soil) was almost normal. There was variation in nitrogen contents, being about normal in Dina and Kharian while it was in low amount (0.12 mgg-1 dry soil) at Jhelum. The number of seeds germinated from the seed stock present in the soil was low at Jhelum (45) and comparatively high at Kharian (58) and Dina (87).
The data relevant to soil features of wheat fields of district Gujrat indicates that the texture of the soil is clay loam throughout the district. The pH value was 8.3, ECe averaged to 2.3 dS m-1and field capacity raged from 60-75%. The amount of organic matter was high at Lala Musa being 5.7 mgg-1 dry soil while it was low (3.9 mgg-1 dry soil) at Gujrat. At other two sites the range of organic matter was in between these two limits which seem to be quite normal. The amount of N appears to be normal in almost all sites of this district ranging from 0.17-0.21 mgg-1 dry soil and the amount of K was also reasonable (0.05 -0.08 mgg-1 dry soil). The amount of P is above 15.25 mgg-1 dry soil in the soils of Bhimber road site, Lala Musa and Gujrat sites but it was comparatively low being 12.70 mgg-1 dry soil in Wazirabad. The amount of seed germinated from the soil seed banks was 59, 95,138 and 155 in Gujrat, Bhimber road site, Lala Musa and Wazirabad sites respectively.
The soil of district Hafizabad was clay loam at two sites while it was sandy loam at Pindi Bhatian. The clay loam soil of two sites had PH 8 ECe, 3.5 dSm-1, and field capacity over 67%. The number of seeds germinated from the seed stock already present in soil was 77, 101 and 125 in Vanika Tarer, Harra Chowk and Pindi Bhatian sites respectively.
The survey of weeds infesting the major crops (cotton, rice, maize and wheat) in various districts of the Punjab revealed many important aspects. A comparison of the existing trend of weed infestation with that recorded during early 1980s, it becomes clear that due to change in cropping pattern and extensive use of herbicides some weeds of become almost weeds of the past. Alternatively a number of weeds were found densely occurring at the periphery of fields due to extensive use of herbicides inside the fields. A new weed (Parthenium hysterophorus) has become very common throughout the Punjab and commonly infesting the surroundings of maize, rice and sugarcane crops as well as the banks of water channels. At some sites it has started infesting the interiors of cultivated crops and in future it may become a potential threat. The degree of weed infestation seems to directly correlate with the income and education of farmers. As such, the fields of progressive farmers had very low degree of weed infestation perhaps due to frequent use of weedicides and intensive cultivation. A similar trend was examined in the soil seed banks as well, which differed with soil type to a great extent. However the subsequent studies may reveal a clear picture of the trends in weed infestation.
The farmers should practice crop rotation and integrated weed control techniques