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Improving Crop and Water Productivity of Rice-Wheat System in Punjab, Pakistan

Riaz A. Mann1, Waqar A. Jehangir2 and I. Masih2

1National Agricultural Research Centre, Islamabad, Pakistan, riazmann5@hotmail.com
2
International Water Management Institute, Lahore, w.jehangar@cgiar.org

Abstract

Wheat and rice are the major food staples for more than 15 million people in Pakistan. The projected demand for the next 25 years will fall short of the supplies by nearly 20 m tons. In order to grow more quality food from marginal/degraded lands and diminishing water resources, the productivity of rice-wheat system must be improved and sustained to make it more viable and eco-friendly. Thus, field experiments were conducted to assess the impact of alternative crop establishment techniques on water productivity of rice-wheat crops. The results revealed that the direct seeding of rice saved 25% water compared to conventional method (transplanted puddled rice). The average water productivity of rice ranged from 0.27 to 0.32 Kg/m3 among the treatments, direct seeding indicating higher water productivity over conventional rice. Significant gains in producing more rice with less water through direct seeding and bed planting were hindered by lower yields mainly due to higher weed infestation. Zero tillage wheat gave better land (4.3 t/ha) and water productivity (1.6 Kg/m3) compared to conventional method, whereas bed planted wheat needs further efforts to improve land and water productivities. Thus, resource conservation tillage technology provides a tool for improving and sustaining water productivity of rice-wheat system, helping with food security and poverty alleviation in Pakistan in the next few decades.

Media Summary

The alternative crop establishment techniques like direct seeding of rice and zero-tillage in wheat emerged as the most efficient methods for increased crop yield and water productivity.

Keywords:

Tillage, Water, Evapotranspiration, Environment, Resource Conservation.

Introduction

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 (Mann and Ashraf, 2001). 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 (Aslam et al., 1993). 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 Pakistan’s Punjab is characterized by a semi-arid climate and 80% of the cropped area is irrigated through tube wells or canals. Due to continuous dry spell over the past several years, both surface and groundwater res

ources are depleting (Gill, 2001). Thus food security in Pakistan will be under serious threat from new emerging challenges, such as production of more quality food from the marginal land and water resources and the development of rice-wheat systems more profitable, sustainable and environment-friendly at less cost. 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) must be evaluated since they play a major role in achieving the above goals. Therefore, studies were conducted to compare the crop establishment techniques in rice-wheat system and to assess the impact of stand establishment on water productivity and sustain the production capacity of resource base in irrigated area of Punjab.

Material and Methods

Three farms in three different watercourses were selected for agronomic and water balance studies. The experiment was laid out in years 2001-02 and 2002-03 with the following four treatments in three replicates:

T1: Direct seeding of rice on flat field (DSF) and Zero tillage wheat (ZT);
T2: Direct seeding of rice on beds (DSB) and wheat on beds with two rows (WB2R);
T3: Transplanting seedlings on beds (TPB) and wheat on beds with three rows (WB3R);
T4: Traditional transplanting of rice (TPR) and traditional method of wheat sowing (TW).

The plot size was approximately half an acre for each treatment. Seeding of rice on flat soil or beds was done about a month earlier (June) than the transplanting of 25-30 days old rice seedlings. The beds (75 cm wide) made during rice planting were retained for wheat crop. The recommended dose of fertilizer, insecticides and herbicides were applied to all the treatments. Rice harvest was completed by mid November and wheat was planted within the next five days. The observations on all the parameters were recorded using standard procedures. Water use was determined by mass balance principle which means inflow (irrigation from canal, groundwater and rainfall) minus outflow (Evapotranspiration, seepage and subsurface outflow). Water productivity (WP) can be expressed as the benefits derived through the use of water, less the costs in producing the benefit and determined by yield/ET (kg/m3).

Results and Discussions:

Water Supply during Rice Season:

The gross inflow was 2.6 times higher than what was potentially demanded during rice season (Fig. 1). A larger part was derived from groundwater (71%), while rainfall and canal contributed to17 % and 12%.

Fig. 1. Gross Inflow and crop demand during rice season

Water Balance in Rice:

The results indicate that the highest amount of water (1490 mm) has to be applied for conventional method (T4) against the least potential crop water requirement (533 mm), showing inefficient use of water as compared to all other treatments. Consequently, direct seeding of rice emerged as the most efficient use of water. It was pertinent to note that for all the treatments, more than 50% of total inflow was not used beneficially by the crop and lost through deep percolation.

Fig. 2. Water balance analysis under various treatments of rice

Water Productivity in Rice:

The conventional method of rice produced the highest paddy yield (3629 kg/ha), followed by transplanting on beds with 3018 kg/ha. The direct seeding gave relative better paddy yield (3404 kg/ha) during 2001. The direct seeded rice suffered badly with high infestation of weeds and diseases. However, the highest water productivity (0.32 kg/m3) was achieved by direct seeding on flat (Figure 3), about 10% higher than the traditional rice planting. Overall, the water productivity of direct seeded rice (either on flat or beds) was better than the transplanted crop. The results suggest that the focus on getting maximum yield alone should not be the prime objective whilst, the productivity of water must also be taken into account. In this respect, direct seeding rice could be a good option as it entails less water as compared to transplanting techniques.

Fig. 3. Water Productivity (kg/m3) in rice during 2001 and 2002.

Water Supply during Wheat Season:

During wheat season, the gross inflow was greater than the potential crop water demand (Fig. 4). However the difference was small compared with the rice crop. The groundwater share in gross inflow was 78 %, while canal and rainfall sources contributed to only 16 % and 6% respectively. This shows that the canal water supply was highly deficient for meeting the water demand of both rice and wheat crops in the area.

Fig. 4. Gross inflow and gross demand during wheat season, 2001-02.

Water Balance:

The water balance results (Fig. 5) indicate that in all cases total inflow or water supply from irrigation and rainfall was lower than the potential crop demand (Evapotranspiration). The total inflow for zero-till crop was 282 mm against the potential demand of 416 mm. The total inflow for T2, T3 and T4 was 254 mm, 266 mm and 291 mm respectively, while the potential demand was in the range of 415-417 mm for all the treatments. This means the wheat crop had slight water stress.

Fig. 5. Water balance (supply vs. demand) of wheat crop.

Water Productivity in Wheat:

The highest yield was obtained with zero-till (4324 kg/ha) followed by 4130 in conventional method. While, the lowest yield was obtained with beds due to poor germination and stand establishment on permanent beds. The Figure 6 shows that zero-tillage gave highest water productivity (1.6 kg/m3), followed by conventional method. The water productivity for raised beds ranged from 1.25-1.35 kg/m3. Similar results were also reported by Malik (2004).

Fig. 6. Water productivity of wheat crop.

There was a tendency to under irrigate wheat crop at all sample farms. The gross inflow to the field also did not differ significantly for all treatments in the command of all the sample farms. Thus, it was likely that the crop used the water entering into the field more efficiently. The farm analysis show that Zaidi Farm showed good irrigation and farm management practices as compared to other two sample farms. The productivity of water emerged as almost equal for wheat cultivated using zero tillage technique and conventional method.

Conclusion

There is a large gap between water supply and demand under farmers’ conventional practices, which needs to be minimized to avert higher groundwater withdrawals and enhance water use efficiencies.

The direct seeding in rice saved about 25% water as compared to conventional method, while water productivity ranged from 0.27 to 0.32 kg/m3, highest with the direct seeding. Significant gains in producing more rice with less water through direct seeding and bed planting were hindered by lower yields mainly due to higher weed infestation that needs to be controlled.

Zero till method in wheat emerged as the most efficient over the conventional method, whereas bed planted wheat needs further efforts to improve land and water productivity.

Further research and developments are needed to ensure higher land and water productivity of direct seeded rice and bed planted rice & wheat for sustainable productivity and management of natural resources in the cereal production system.

Reference

Mann RA and Ashraf M. (2001). In ‘Specialty Rices of the World: Breeding, Production and Marketing’. (Ed. RC Chaudhary; DV Tran and R. Duffy). Food and Agricultural Organization, Rome, Italy.

Aslam M., Majid A, Hashmi NI and Hobbs PR. (1993). Improving wheat yield in the rice-wheat cropping system of Punjab through zero tillage. Pakistan Journal of Agri. Research, 14: 8-11.

Gill MA (2001). Proceedings of the International workshop on conservation agriculture for food security and environment protection in rice-wheat cropping system. Feb. 6-9, 2001. Lahore, Pakistan.

Malik, RK (2004). Proceedings of the 12th Regional Coordination Committee Meeting, February 7-9, 2004. Islamabad, Pakistan.

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