Zero-tillage rice establishment and crop-weed dynamics in rice and wheat cropping systems in India and Australia

During 2006, significant progress was made against all project objectives, involving the collaborative efforts of the researchers from the institutes of CCS Haryana Agricultural University (HAU), Punjab Agricultural University (PAU), Rice-Wheat Consortium (RWC) and the University of Adelaide (UA), to investigate zero-tillage rice establishment and crop-weed dynamics in rice and wheat cropping systems of India and Australia.

Excellent progress has been made in the development of baseline information required for the successful establishment of direct seeded rice (DSR) as a productive and sustainable alternative to conventional hand-transplanted system. Several field sites (n=35) were established across states of Haryana, Punjab and Bihar. These states geographically provide an excellent cross section of the Indo-Gangetic plains in terms of climatic and productivity status. Consultation amongst principal scientists, researchers and growers from each region, identified local issues to be investigated within the proposed objectives of LWR/2004/033. More specifically, key experimental questions addressed in the first year of the project for DSR systems included (a) direct validation of rice productivity in comparison to hand-transplanted puddle system, (b) identification of optimal rice sowing densities and times, (c) evaluation and suitability of different rice genotypes, (d) identification of weed recruitment/dynamics and potential shifts in weed flora, and (e) development of robust weed management strategies.

Comparative evaluation of DSR against the traditional hand-transplanted system showed a yield depression was associated with zero-tillage establishment in Punjab (20 to 73%), and Bihar (23%) sites, respectively. However, optimising sowing time and seeding rates (40-60 kg/ha) of rice significantly reduced the yield penalty associated with zero-tillage (=7%). Data from sites in Punjab and Bihar showed that rice yields were statistically non-significant between DSR and transplanted systems when sowing dates were similar for the systems. The maturity profile (short versus long) of rice cultivars was also shown to be an important characteristic to final yield outcomes and requires further investigation.

In addition, grower field sites (n=17) were established in Haryana to evaluate the performance of basmati and coarse grain rice established under zero-till and puddle transplant systems. Preliminary data is extremely encouraging showing similar yields for Zero-till (2275 to 6800 kg/ha) and traditional puddle transplant systems (2325 to 7625 kg/ha). It is expected that ongoing interaction between the researchers and growers on alternative rice production systems will greatly facilitate the on-farm adoption of DSR.

Emphasis was also placed on identifying suitable rice genotypes for DSR, with rice breeding lines and cultivars sourced from local breeding programs. Several genotypes (n=33) differing in maturity (short, medium & long) and vigour were evaluated under DSR and transplanted systems at sites in Punjab and Bihar. It was encouraging to note that some of the advanced breeding lines produced similar yields under DSR and transplanted systems. However, it is important that these data be revalidated in 2007, to show the effects of seasonal variation on these genotype sowing system responses. In 2007, It is anticipated that additional breeding lines will be sourced from the International Rice Research Institute (IRRI) and Indian breeding programs and evaluated for suitability under DSR system.

An experiment undertaken in Bihar investigating weed establishment under DSR and transplanted rice showed that final weed densities (grassy, broadleaf and sedges) were similar for the different crop establishment systems (248 to 457 plants/m2). However, a significant shift in the weed spectrum resulted with fewer grassy weeds (48 to 83 plants/m2) establishing in zero-till DSR as compared to the transplanted system (220 plants/m2), respectively. Significant shifts in weed flora under DSR will have important implications for the management and the potential development of herbicide resistance. History has shown that herbicide resistance development (i.e. Phalaris minor) can be a major constraint to the productivity and sustainability of rice-wheat systems in India. Research undertaken as part of project LWR/2004/033 will closely monitor the resistance status of weeds under DSR.

Experiments evaluating different herbicide options for DSR identified useful mixtures (i.e. azimsulfuron + metsulfuron) for the control of broadleaf and sedge weeds (see attached reports). Useful options for controlling grass weeds in DSR were limited; however, herbicide Bispyribac provided excellent control (90%) of Echinochloa crus-galli (Barnyard grass) at sites in Haryana. High levels of weed control obtained with Bispyribac resulted in a 3-7 fold increase in rice yield compared to the weedy controls. Identification of useful herbicides for DSR will continue in 2007.

Data from Australian experimental work was extensive in 2006, with collection of important information on water and nutrient use efficiency in wide-row (WR) cropping under well below average growing season rainfall. In addition, replicated experiments were established investigating the performance and suitability of different crop species and their cultivars to WR cropping. These experiments have identified cultivars showing greater suitability to WR cropping and have consequently been repeated this year. Field experiments were also established investigating weed behaviour and management opportunities in WR cropping. Preliminary data has shown that WR systems appear to be less conducive to the establishment of problematic weeds such as annual ryegrass (ARG). Furthermore, strategic intra- and inter-row herbicide applications were shown to provide high levels of ARG control, and significant crop yield increases. Future research will be undertaken in farmer fields to investigate weed population dynamics under wide-row zero-till cropping systems.

During 2007, significant progress was made against project objectives involving collaborative efforts of researchers from CCS Haryana Agricultural University (HAU), Punjab Agricultural University (PAU), Rice-Wheat Consortium (RWC) and the University of Adelaide (UA), to investigate zero-tillage rice establishment and crop-weed dynamics in rice-wheat cropping systems of India and Australia.
During the reporting period excellent progress was made against project milestones in the identification and development of suitable establishment systems for direct seeded rice (DRS) as an alternative to the traditional hand transplanting method. Several field sites (n=35) were established across states of Haryana, Punjab and Bihar. Research activities focused on a) direct validation of DSR establishment systems against traditional hand-transplant technique, b) identification of optimal sowing times and seeding rates, c) evaluation and suitability of different rice genotypes, d) identification of weed recruitment/dynamics and potential shifts in weed flora and e) development of robust weed management systems.
Yield responses for coarse grain and basmati rice types were similar under comparative evaluations of DSR against traditional hand-transplant system at sites across states of Haryana, Punjab and Bihar. At 2 of the 3 sites established across Punjab there was no significant difference in yield between rice establishment systems, only at Kapurthala which has a sodic soil, rice yields were significantly higher (44-85%) in the traditional hand-transplant system. In contrast, rice established under zero-tillage at PUSA, Bihar, yielded significantly more grain (9-39%) than the traditional hand-transplant system. Similarly, higher yields were obtained with zero-tillage machine transplanted (8.3 t/ha) rice than the conventional puddled transplanted (7.5 t/ha) treatment at Kurukshetra research station, Haryana.
In addition, grower field sites (n=6) were established in the states of Haryana and Punjab to evaluate the performance of basmati and coarse grain rice established under DSR and puddle transplant systems. The results from grower fields in Haryana have been extremely encouraging with similar yields under DSR Basmati (2.6-2.9 t/ha) and the traditional puddle transplant system (2.4-3.1 t/ha). Preliminary results from sites in Punjab were also encouraging with yields in excess of 7.9 t/ha under DSR. Grower feedback from these results has been extremely positive, with some growers planning to investigate DSR on a larger scale in 2008. Furthermore, continual interaction between researchers and growers on alternative rice production systems is expected to greatly enhance on-farm adoption of DSR.
Experiments undertaken in Punjab and Bihar investigating optimal rice sowing densities and time clearly showed that yields were maximised for DSR when it was sown on the same day as nursery sowing for the transplant system, and when seeding rates were maintained at between 45-60 kg/ha (150 plants/m2). Furthermore, increased seeding rates were also shown to greatly improve the rice crops competitiveness with weeds such as Echinochloa and Panicum spp., resulting in significant reductions in weed growth (33-35%) and improved crop yields (27-62%).
For the second year, experiments were undertaken in Punjab and Bihar to assess the performance of several rice genotypes (n=44) under DSR and comparative puddle transplant systems. The evaluation consisted of rice breeding lines, hybrids and cultivars, sourced from International Rice Research Institute (IRRI) and local Indian breeding programs. It was encouraging to see that several of the advanced lines, produced similar yields under DSR and transplant system. Breeding line 17A/R10, sourced from IRRI performed well under DSR (5.7 t/ha) in comparison to transplant system (5.2 t/ha) at PAU. Furthermore, hybrid genotypes evaluated in Bihar performed particularly well under DSR producing some of the highest grain yields (4.6-5.6 t/ha) in the study. The performance of basmati genotypes under DSR in Bihar is also noteworthy, with 5 of the 7 genotypes evaluated under this system producing equivalent yields to the puddle transplant system. It is anticipated that further genotype screening will occur in 2008, with additional breeding lines sourced from IRRI and local Indian breeding programs.
An experiment undertaken in Haryana, investigating weed establishment under puddled and unpuddled DSR and transplanted rice showed significant shifts in weed spectrum (grassy, broadleaf & sedges) under different crop establishment systems. Clear associations were found with Echinchloa, Leptochloa and Fimbristylis spp. showing greater establishment under DSR in comparison to the transplant system. Furthermore, there was greater establishment of Echinochloa under puddled conditions and Leptochloa under unpuddled conditions. In contrast, Cyperus difformis which is a sedge showed clear preference for the unpuddled transplant system. These clear differences in weed spectrum with the different rice establishment systems require further investigation. Studies are needed to investigate the effect of crop establishment system on the behaviour of weed seedbank. In June 2008, it is anticipated that studies on weed seedbank behaviour will be undertaken following a visit from the Australian project research officer (PRO) based in Adelaide.
Useful herbicide options identified in 2006 for controlling weeds in DSR (i.e. azimsulfuron and bispyribac) were evaluated further at sites in Haryana, Punjab and Bihar. Research focused on optimising herbicide application rates, timing and mixtures. Herbicide bispyribac continued to provide excellent control of grass (Echinochloa spp.) and sedge weeds (Cyperus spp.) at sites across all 3 states. This herbicide was particularly effective when applied at higher rates (25-30 g/ha) and early application timings (15-20 DAS). However, in an on-farm study at Kolhar bispyribac provided effective control of E. crusgalli even at the panicle emergence stage of the weed. Azimsulfuron provided effective control of broadleaf weeds, particularly when used in combination with metsulfuron. Importantly, there appears to be good selectivity with these herbicides in rice, with high levels of weed control resulting in increased grain yield. Further evaluation of these herbicides is planned for 2008.
Experiments undertaken in Australia provided second year of comprehensive data on water and nutrient use-efficiency in wide-row (WR) cropping. In addition, experiments evaluating the suitability of different crop species and their cultivars to WR were repeated. In 2007, additional crop types canola and chickpeas and their cultivars (n=6) were included for evaluation under WR systems. These experiments have been extremely useful in identifying cultivars with greater suitability to WR systems. Furthermore, positive results from these trials have prompted significant interest amongst the farming community with some growers adopting WR for the first time. Field experiments were also undertaken to investigate weed behaviour and management under WR. Results have again shown that WR systems significantly reduce the establishment of problematic weeds such as annual ryegrass (ARG). Furthermore, experiments established that ARG can be successfully controlled in WR systems with strategic intra- and inter-row herbicide applications. Research activities planned for 2008 will focus on investigating weed dynamics and management under WR cropping systems.