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Rice-Wheat Cropping Pattern and Resource Conservation Technologies                                   
By Iftikhar Ahmad
      Shazia Iram

1. Deputy Director General, Institute of Plant and Environmental Protection (IPEP), National Agriculture Research Centre (NARC), Islamabad.
2. Assistant Professor, Department of Mycology and Plant Pathology, University of the Punjab, Lahore.

The rice-wheat system has been practiced by farmers in Asia for more than 1000 years. It has since expanded and is currently estimated at 23.5 million ha. The rice-wheat system covers 13.5 million ha in South Asia: India (10.0), Pakistan (2.2), Bangladesh (0.8) and Nepal (0.5). It represents 32% of the total rice area and 42% of the total wheat area in these countries.

In the Indo-Gangetic Plains (IGP), which stretches across these four countries, rice is usually grown in the wet summer (May/June to October/ November) and wheat in the dry winter (November/ December to February/March). Although rice-wheat cropped area in the IGP is irrigated or has assured rainwater in sub-humid regions, the soils and crop management undergo drastic changes during the two cropping seasons. Several yield-reducing and yield limiting factors, together with delayed planting of wheat and transplanting of rice; energy, labor, and other input shortages; resistance of the weed and crop residue burning have contributed to the stagnating or declining production, productivity and sustainability of this system.

Continuous cropping of rice-wheat system for several decades as well as contrasting edaphic needs of these two crops have resulted in increased pest pressure, nutrient mining, and decline in yields in some areas. In many areas, yields have stagnated at below potential level. The input use efficiency is low. Soil organic matter content has reduced. This can be improved by incorporating crop residue into the soil. But burning of crop residue is common and has increased environment pollution. Nutrients are being mined and transported long distances and lost permanently for the sub region. The water table has receded at several places in the region. Also, there is a reduction in biodiversity due to large area coverage by a single cultivar.

Rice-Wheat Cropping System in Punjab

The rice-wheat growing areas in Pakistan are primarily situated in central Punjab (main districts include Gujranwala, Sheikhupura, Narowal and Sialkot) followed by Sindh (Fig 1). The rice-wheat cropping system in Pakistan is the major one with an estimated area of 1.6 mha. In the system, rice is traditionally grown by transplanting 25-35 days old seedlings in well-puddled and continuous flooded field. This method of rice establishment is a time-consuming, tedious and inhuman and involves high cost of labour, water, and land preparation. Wheat sowing after the paddy harvest is delayed, resulting into poor crop stand and low grain yield. Wheat crop is also badly affected by flood irrigation due to poor drainage of paddy soils. Consequently, the productivity of the system remains far below the potential yield levels of modern cultivars.

The rice-wheat system, one of the major cropping systems of the South Asia and parts of East Asia, requires special management. Rice grows well on puddled compacted soil, whereas wheat grows best on well-drained soils. The hardpan developed with puddling operation is important for water retention and weed control in rice, but compacted soil creates problems of waterlogging for wheat. In addition to this, the traditional land preparation after rice harvest results in later wheat sowing dates than optimum. Due to these management differences and traditional cultural cultivation practices, the productivity of the rice-wheat system is stagnating and its sustainability threatened.

This can only be possible if the planting techniques of rice or wheat crops are improved resulting to saving of time, cultivation cost and irrigation water. Resource conserving technologies (e.g. zero-tillage, bed planting or direct seeding of rice) can be helpful in the achievements of major goals.

Resource-conserving technologies
Resource-conserving technologies are defined here as any practice that improves the efficiency of use of natural resources, including water, air, fossil fuels, soils, inputs, and people.
Late planting is a major problem in most rice-wheat areas. To improve system productivity, the wheat crop must be planted at the optimal time.

The other major cause of late wheat planting is the long turnaround time between rice harvest and wheat planting. Long turnaround can be caused by many factors, including excessive tillage, soil moisture problems (too wet or too dry), lack of animal or mechanical power for plowing, and the priority farmers place on threshing and handling the rice crop before preparing land for wheat.

Coupled with the problems of late planting of wheat is the problem of poor germination and plant stands. Most farmers in the IGP sow wheat by broadcasting the seed into plowed land and incorporating it by another plowing. Part of the reason for this is residue management problems in fields following rice. The loose straw and stubbles are raked and clog the seed drills. Broadcast seed results in seed placement at many different depths and into different soil moistures, with resulting variable germination. The problems of late planting and poor plant stand have been addressed by promoting various resource-conserving tillage and crop establishment techniques described below

a) Surface Seeding
Surface seeding is the simplest zero-tillage system being promoted. In this tillage option, wheat seed is placed onto a saturated soil surface without any land preparation. This is a traditional farmer practice for establishing wheat, legumes and other crops.

b) Zero-Tillage with Inverted-T Openers
Another practice involves sowing using a seed drill, without prior land preparation. This has been tested in Pakistan and is presently being tested in other areas of the Indo-Gangetic Flood Plains, including India and Nepal. The practice is more relevant in the higher yielding, more mechanized areas of northwestern India and Pakistan, where most land is prepared using four-wheel tractors.

c) Reduced Tillage
The Chinese have developed a seeder for their 12 horsepower, two-wheel diesel tractor that prepares the soil and plants the seed in one operation. This system consists of a shallow rotovator followed by a six-row seeding system and a roller for soil compaction. Funding from the UK Department for International Development (DFID) and CIMMYT made it possible to import several tractors and implements from Nanjing, China, into Nepal, Pakistan, and India, where they have been tested over the past few years with positive results.

The main drawback of this technology is that the tractor and the various implements are not easily available and spare parts and maintenance are hard to obtain. It would help if the private or public sector in South Asian countries could import this machinery or develop a local manufacturing capability.

d) Bed Planting Systems
In bed planting systems, wheat or other crops are planted on raised beds. This practice has increased dramatically in the last decade. Farmers have given the following reasons for adopting the new system:

Management of irrigation water is improved.
Bed planting facilitates irrigation before seeding and thus provides an opportunity for weed control prior to planting.
Plant stands are better.
Weeds can be controlled mechanically, between the beds, early in the crop cycle.
Wheat seed rates are lower.
After wheat is harvested and straw is burned, the beds are reshaped for planting the succeeding soybean crop. Burning can also be eliminated.
Herbicide dependence is reduced, and hand weeding and roguing is easier.
Less lodging occurs.

Such technologies are rapidly gaining popularity among farmers, in as much as they increase production and lower costs, resulting in higher profits, cheaper food, and improved farmer livelihoods. Among other things, the efficiencies gained include less land and time needed to produce the required staple cereals, allowing farmers to diversify crops and cropping patterns or pursue other gainful activities.;

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