Weeds: Major Productivity Limiting Factor for Agronomic Crops in Pakistan | List of weeds

Weeds pose a significant biological challenge to agricultural productivity, leading to reduced crop yields, decreased quality, increased pest and disease incidence, and additional costs of production. In this article, we will delve into the detrimental effects of weeds on agricultural output, examining their competition with main crops, allelopathic results, and specific examples of significant fodder crops and their associated weeds in Pakistan.

Weed Competition with Main Crops: 

Weeds compete with main crops for essential resources such as space, light, moisture, and nutrients, including nitrogen, phosphorus, and potassium. It has been observed that weeds can take up double the amount of nitrogen and phosphorus and triple the amount of potassium compared to crop plants.

Furthermore, weeds have a higher potential for seed production, with some species producing significantly more seeds than a single crop plant. On average, weed infestation can lead to yield reductions of up to 42%, depending on weed density and nature.

Impact of Weeds on Fodder Crops: 

Fodder crops, essential for livestock feed, are particularly vulnerable to weed infestations. Egyptian clover, for example, suffers from significant reductions in green fodder and seed yield due to weed flora. Weeds like Rumex dentatus, Cichorium intybus, and Sonchus asper make it challenging to harvest Egyptian clover, further hampering productivity.

In general, weed infestations can cause yield reductions of 25-35% for green fodder and seed production, negatively impacting the quality of the fodder.

Allelopathic Effects of Weeds: 

Weeds also exert allelopathic effects on crops, referring to their ability to release chemicals that stimulate or inhibit the growth of other plants. These chemical compounds are released through root exudation, leaching, volatilisation, and decaying plant tissue. Allelopathic effects vary among different weed species, with various plant parts exhibiting distinct impacts on the germination and seedling development of crops. Even at low concentrations, allelopathic chemicals can impair crop seedling growth due to the complex interactions of chemical classes present in weeds, including phenolic compounds, alkaloids, flavonoids, steroids, terpenoids, and amino acids.

Major Fodder Crops and Associated Weeds in Pakistan: 

In Pakistan, fodder cultivation is conducted in two seasons: Summer or Kharif season (April to September) and Winter or Rabi season (October to April). During the lean periods of June-July and December-January, when one season’s crops are being harvested, fodder scarcity becomes prominent. The following tables outline major fodder crops and their associated weeds in Pakistan:

Major weeds found in fodder crops 

Winter or Rabi season weeds

Summer (Kharif) weeds

Perennial weeds (lawn+aquatic)

Conclusion: 

Weeds represent a significant biological constraint to agricultural output, affecting crop yields, quality, and the overall efficiency of farming operations. The competition for vital resources, allelopathic effects, and the challenges they pose in specific crops, such as fodder, demand effective weed control strategies to mitigate their negative impacts and ensure sustainable agricultural practices. By understanding the intricate dynamics between weeds and crops, farmers and researchers can develop targeted approaches to manage weed infestations and improve agricultural productivity.

Muhammad Abdullah Saleem¹, Asif Iqbal¹, Umair Gull¹, Muhammad Amir Iqbal², Rana Nadeem Abbas¹, M. Shahbaz Naeem¹, Abid Shehzad¹, Wajeeh-Ur-Rehman¹, Shawaiz Iqbal⁴, Usama-Bin-Khalid⁴, Saira Jamil³, Maaz Aslam¹, Mehboob Ali¹, Summaya³, Sidra Arshad³

• Department of Agronomy, University of Agriculture, Faisalabad¹ and University of Poonch, Rawalakot², Pakistan
• Department of Botany, Faculty of Sciences, University of Agriculture, Faisalabad³
• Rice research institute Kala Shah Kaku⁴