Among these challenges, weed management remains particularly important. Phalaris minor (little seed canary grass), locally known as Gulli-Danda, is one of the most troublesome weeds of wheat in the rice–wheat system. Its close resemblance to wheat during early growth makes it difficult to identify, while repeated use of similar herbicides has contributed to resistance problems in some areas.
In this situation, the choice of tillage system can play an important role in determining weed emergence and the effectiveness of weed management practices.
Two contrasting approaches to wheat establishment
Traditionally, wheat has been grown after several tillage operations following rice harvest. The field is prepared through ploughing, harrowing and leveling before sowing. This conventional tillage (CT) system incorporates or partially removes rice residues and creates a relatively clean seedbed.
In contrast, zero-tillage (ZT) allows wheat to be directly sown into the standing rice residues with minimal soil disturbance. With appropriate machinery, wheat can be established quickly after rice harvest while a considerable amount of rice residue remains on the soil surface.
Thus, the two systems create quite different soil and residue environments for weed emergence.
How rice residues influence weeds
Retaining rice residues on the soil surface can act as a physical barrier to the emergence of certain weeds. The residue layer can reduce the amount of light reaching the soil surface, modify soil temperature and moisture, and physically hinder the emergence of weed seedlings.
This effect can be particularly useful against weeds whose seeds are located near the soil surface. However, residue retention should not be considered a substitute for an effective weed management programme. Phalaris minor and other weeds may still emerge through or around the residue layer, particularly when residue distribution is uneven.
Therefore, the major advantage of residue retention is not necessarily complete weed suppression, but alteration of the weed population and its emergence pattern, which can be integrated with chemical and non-chemical weed management.
Zero-tillage: an opportunity for integrated weed management
Zero-tillage wheat offers several agronomic advantages beyond weed management. It enables rapid wheat establishment after rice harvest, reduces the number of tillage operations, saves fuel and time, and facilitates timely sowing.
Timely sowing itself is an important component of weed management. When wheat is sown on time, the crop establishes rapidly and competes more effectively with weeds.
In a ZT system with retained rice residues, the crop therefore benefits from two complementary effects:
timely crop establishment + residue-mediated suppression of some weeds.
However, successful weed management under ZT requires proper residue spreading, suitable seed placement and timely application of herbicides when needed.
Conventional tillage: does soil disturbance always control weeds?
Conventional tillage can destroy emerged weeds and prepare a relatively weed-free seedbed. However, repeated soil disturbance also redistributes weed seeds within the soil profile.
Some weed seeds brought close to the soil surface may find favourable conditions for germination. Consequently, conventional tillage may provide initial weed control without necessarily reducing the long-term weed seed bank.
Moreover, repeated tillage requires additional tractor operations, labour and fuel. Delays in field preparation after rice harvest can also result in delayed wheat sowing, which may give winter-season weeds a competitive advantage.
Thus, the comparison should not simply be viewed as “tillage versus no tillage”. The more relevant question is which system allows timely crop establishment while maintaining effective and sustainable weed management.
What happens to Phalaris minor?
Phalaris minor has historically been a major constraint in the wheat-growing regions of north-western India. Its management has become increasingly complex because of herbicide resistance and changes in cropping and tillage practices.
Under ZT with rice residue retention, the residue layer can influence the emergence and density of P. minor. At the same time, the absence of intensive soil disturbance changes the distribution of weed seeds and the conditions under which they germinate.
This means that the weed management strategy used under conventional tillage cannot always be transferred directly to zero-tillage fields. Herbicide selection, application timing, spray technique and residue conditions need to be considered together.
Where does metribuzin fit into the system?
Metribuzin is an important herbicide option for wheat and can provide control of P. minor along with several broad-leaved weeds when used according to recommendations.
Research conducted under rice-residue-retained, zero-tillage wheat has demonstrated that the timing and method of metribuzin application can substantially influence weed control and crop performance. In particular, post-emergence application strategies deserve attention under residue-retained conditions.
This highlights an important principle:
A herbicide should not be considered independently of the production system in which it is being used.
The same herbicide may behave differently depending on crop stage, weed stage, residue cover, soil conditions, application technique and environmental conditions.
A practical comparison for Haryana farmers
|
Aspect |
Zero-tillage + rice residue |
Conventional tillage |
|
Soil disturbance |
Minimal |
High |
|
Rice residue |
Retained on surface |
Usually incorporated/removed |
|
Field preparation |
Faster |
More time and operations required |
|
Fuel requirement |
Lower |
Higher |
|
Timely wheat sowing |
Easier to achieve |
May be delayed |
|
Weed emergence |
Modified by residue and limited disturbance |
Influenced by repeated soil disturbance |
|
P. minor management |
Requires system-specific strategy |
Conventional herbicide-based strategy often used |
|
Long-term approach |
Well suited to integrated weed management |
Greater dependence on tillage operations |
What should farmers adopt?
There is no single weed-control practice that can solve the problem of P. minor permanently. A more sustainable approach is Integrated Weed Management (IWM).
For Haryana's rice-wheat system, this may include:
-
Timely sowing of wheat.
-
Properly distributed rice residue retention.
-
Zero-tillage where field and residue conditions are suitable.
-
Regular monitoring of minorand broad-leaved weeds.
-
Rotation of herbicide modes of action rather than repeated dependence on one herbicide.
-
Use of recommended herbicide doses and application methods.
-
Crop diversification wherever feasible.
-
Preventing weeds from reaching maturity and replenishing the soil seed bank.
The way forward
The future of wheat production in Haryana requires a shift from “weed killing” to “weed management.” Zero-tillage with rice residue retention provides an opportunity to combine conservation agriculture with integrated weed management.
Conventional tillage can provide short-term weed suppression through soil disturbance, but it also involves greater energy use and may not address the underlying weed seed bank. Zero-tillage, on the other hand, changes the weed environment and can facilitate timely wheat establishment, but it requires more precise and system-specific weed management.
Therefore, the choice should be based on the whole production system rather than on tillage alone.
For Haryana farmers, strategy can be: retain and manage rice residues properly, sow wheat on time, monitor weeds regularly, and use herbicides judiciously and according to recommendations. Such an integrated approach can help maintain wheat productivity while reducing cultivation costs and supporting more sustainable rice–wheat production.
Autors
Isha Ahlawat, BR Kamboj, Dharambir Yadav
Department of Agronomy,
Chaudhary Charan Singh Haryan Agricultural University, Hisar-125004, Haryana
