In South Asia's rice-based cropping systems, most farmers flood and repetitively till their fields before transplanting. This establishment method, commonly termed puddled transplanted rice (TPR), is costly. In addition, it is labor and energy intensive. To increase labor and energy efficiency in rice production, reduced or zero-tilled direct seeded rice (ZT-DSR) is commonly proposed as an alternative tillage and crop establishment (TCE) option. Effective management of weeds in ZT-DSR however remains a major challenge. We conducted a four-year experiment under a rice-maize rotation in Northwestern Bangladesh in the eastern Gangetic Plains to examine the performance of two TCE methods and three weed management regimes (WMR) on the diversity and competitiveness of weed communities in the rice phase of the rotation. The Shannon-Weiner Diversity Index, a measure of species diversity, was significantly greater under ZT-DSR than puddled TPR. It was also greater under no weed control (Weedy) and two manual weeding (MW) treatments compared to chemical herbicide with manual weeding (C + MW). In DSR Weedy plots, weed communities began shifting from grasses to sedges from the rotation's second year, while in the ZT-DSR and C + MW treatments, sedges were consistently predominant. In both puddled TPR Weedy and TPR C + MW treatments, broadleaves and grasses were dominant in the initial year, while sedges dominated in the final year. There were significant main effects of year (Y) and weed management regime (WMR), but not of TCE. Significant Y × TCE and TCE × WMR interaction effects on rice yield were also observed. Grain yields under ZT-DSR were similar to puddled TPR. ZT-DSR with one application of pre-emergence herbicide followed by one hand weeding at 28 days after establishment however resulted in significantly higher grain yield (5.34 t ha-1) compared the other weed management regimes. Future research should address methods to effectively manage weed community composition shifts in both ZT-DSR and TPR under rice-maize rotations utilizing integrated and low-cost strategies that can be readily applied by farmers in the eastern Gangetic Plains.

Farmers in the rainfed salt-affected coastal areas of eastern India face challenges of flooding, salinity, scarcity of irrigation water, and insufficient rainfall that affect crop production and environmental sustainability. This study evaluated three rice establishment methods [dry-seeded rice (DSR), non-puddled transplanted rice (Non-PTR), and puddled transplanted rice (PTR)] during the wet season/kharif and three tillage practices [zero-tillage (ZT), conventional tillage (CT), and raised-bed sowing (RBS)] for dry-season/rabi crops (maize and rapeseed) in a replicated experiment. The experimental site was in the rainfed and salt-affected coastal lowland area of West Bengal, India, and rice was grown in three successive wet seasons (2013-16), with each rice crop followed by maize or rapeseed in the dry season. Transplanted rice was adversely affected by submergence each year due to heavy rain after transplanting, whereas DSR was less affected as the plants were taller at the time the heavy rains began. Rice grain yields were similar (4.5-5.1 t ha(-1)), however, among the three rice establishment methods, and, further, rice yields were not affected by rabi-season tillage practices. The net returns and the benefit-cost ratio (BCR) were greater in DSR because of the reduced costs of land preparation. Rapeseed grown after non-puddled rice (DSR and Non-PTR) gave 25-44% higher yield than rapeseed grown after PTR, and the yields of maize were 8-13% higher when grown after either DSR or Non-PTR than after PTR. DSR and Non-PTR also had positive effects on soil quality: bulk density was lower after the third-year rice crop and soil salinity decreased during each dry season (Dec-April) just after the rice crop compared with PTR. Maize yield was highest in RBS (5.8 t ha(-1)), followed by CT (4.1 t ha(-1)) and ZT (3.6 t ha(-1)), whereas rapeseed produced the highest yield under ZT (0.86 t ha(-1)) vis-a-vis RBS and CT (0.6 t ha(-1)). Net returns for maize were highest with crops on RBS and in rapeseed with ZT. Maize provided a higher economic return than rapeseed (USD 301-405 ha(-1) in maize; USD 5-113 ha(-1) in rapeseed) but it (maize) required 25 cm more irrigation water and 3 GJ ha(-1) more energy input for cultivation. This study indicates that rice-maize could be more profitable than rice-rapeseed for the salt-affected coastal areas in India, and that, to improve productivity and profitability in this rotation, rice should be established as DSR or Non-PTR followed by maize on FIBS in the coastal regions.

Sampling design influences the accuracy and confidence that an investigator can place on the information derived from a data set. This study was undertaken to quantify the influence of systematic and random sample designs on the estimation of stubble height. Variance estimates, data set range, adequate sample size, and relative variation were greater with the systematic sampling design, and mean estimates were lower when compared with estimates derived from a random sampling design.

Rodents and weeds are important pests to rice crops in Southeast Asia. The interaction between these 2 major pests is poorly documented. In temperate cereal systems, seeds of grass weeds can be an important food source for rodents and weed cover along crop margins provides important refuge for rodents. In 2012 and 2013, a replicated study (n = 4) in Bago, Myanmar compared 4 treatments (rodents and weeds; no rodents and weeds; rodents and no weeds; no rodents and no weeds) each of 0.25 ha in transplanted rice. Weeds were managed with hand weeding in the wet season, and hand weeding and herbicides in the dry season. Plastic fences were installed to exclude rodents. We examined the weed cover and relative abundance of weed species, rodent damage, rodent population dynamics and rice yield loss caused by rodents and weeds. The dominant rodent species was Bandicota bengalensis. In the dry season, Cyperus difformis was dominant at the tillering stage and Echinochloa crus-galli was the dominant weed species at the booting stage. In the wet season E. crus-galli was a dominant weed throughout the season. Damage by rodents was higher in the dry season. There were larger economic benefits for best weed management and effective rodent control in the dry season (258 US$/ha) than in the wet season (30 US$/ha). Concurrent control of weeds in and around rice fields combined with coordinated community trapping of rodents during the early tillering stage and ripening stage of rice are recommended management options.

As scientists working at the International Rice Research Institute and other institutions that have investigated greenhouse gas emissions from rice fields, we read the recent article in PNAS by Kritee et al. (1) with great interest. The observed N2O emissions from rice fields in South India including previously unknown high rates definitely constitute an important finding that warrants being reported. We also agree that recommendations on farming practices should give close attention to timing and rates of N fertilizer application in relation to water management. Other generalizations in this study, however, are largely unfounded and speculative. We raise several critical issues that are further substantiated by information … [↵][1]1To whom correspondence should be addressed. Email: r.wassmann{at}irri.org. [1]: #xref-corresp-1-1

Soil freeze-thaw cycles can result in soil surface crusting, pedestaling, and movement. This study was undertaken to quantify the amount of heaving and soil moisture migration in a silt loam soil from the sagebrush steppe. Soil columns containing silt loam soil with moisture treatments of 26%, 34%, 42%, or 50% water content and initial temperatures of 9o C or 20o C were exposed to − 7o C for 18 h, which did not completely freeze the soil to full depth. Moisture redistribution amounts of 10% to 20% were observed in treatments above field capacity. Surface saturation was observed after freezing with treatments of 42% and 50% water volume. Soil heaving of up to 0.5 cm was observed after one freezing event.

Large areas of lowlands within tidal deltas have been reclaimed for crop production in Indonesia. However, major production constraints such as floods, seawater intrusion from tidal rivers, and adverse soils remain a significant problem, resulting in low rice yields (2-3 t ha(-1)) and production systems that are prone to risk. This review describes the recent progress in technology development, to address multiple abiotic stresses through the genetic improvement of rice. During the last 15 years, rice breeding programs and germplasm evaluation systems for coastal deltas have been revitalized. Local landraces, modern varieties and elite stress-tolerant genotypes were screened and physiological response to the stress and agronomic performance of promising genotypes were characterized. These efforts resulted in the release of the first series of flood- and salinity-tolerant varieties for lowlands in Indonesia. On-farm trials with these varieties demonstrated yield advantages of up to 125%, over popular varieties currently used by farmers in the marginal lowlands. Some of these varieties made an impact; Ciherang-Subl, a submergence-tolerant variety near-isogenic of Indonesia's popular variety (Ciherang), occupied over 430,000 ha of rice lowlands within four years of its release in 2012. There are large "exploitable yield gaps" between the attainable farm yield and mean farm yield, and appropriate crop and natural resource management guidelines for the new rice varieties are being developed. These achievements highlight opportunities for sustainable development in unfavorable rice environments of coastal deltas and are relevant to other areas in South and Southeast Asia.

Water developments have been considered a fundamental tool for dispersing livestock and reducing livestock impact on riparian and aquatic habitats associated with perennial streams. Quantifying the efficacy of water developments has been difficult because of the need to continuously monitor water sources for the timing and intensity of use. The advent of global positioning system (GPS) tracking technology has largely overcome this hurdle and presented new research opportunities. We conducted a five-year study to quantify and evaluate the relative use of existing water developments by cattle on three extensive study areas in northeastern Oregon, United States. Ten randomly selected beef cows from herds grazing each study area were fitted with GPS collars recording animal positions at five-minute intervals throughout the grazing season. Cattle occupancy in 60 m (196.9 ft) buffers around water developments was determined monthly and annually. Use of water developments was contrasted with that of riparian zones. Cattle use of water developments varied substantially from site-to-site, month-to-month, and year-to-year. In some months, cattle watered exclusively from off-stream developments, and in others, cattle watered nearly exclusively from streams. Substantial differences in the relative use of individual water developments were also seen by season and year. Some developments received no use at all during the five-year study while others were visited frequently. Our results suggest off-stream water development is a useful managerial strategy, but careful placement is required to improve the likelihood that cattle will find and use these water sources and thus decrease their dependence and use of permanent streams and associated riparian areas.

Stream and riparian health is a major concern for state and federal land management agencies that are charged with oversight of extensive land holdings in the mountain west of the United States. Several federal agencies in the 19805 and 1990s determined that livestock grazing had adversely impacted a majority of federal lands in this region. In response, management was.changed on grazing allotments to focus on stream system health. Recent advanced global positioning system (GPS) logging capabilities, both accuracy and frequency/duration of logging, coupled with rapidly developing geographic information system (GIS) analytical capabilities allowed evaluation of livestock use of streams and riparian zones on mountain rangelands. This study was undertaken to clarify spatiotemporal characteristics of cattle use of perennial streams and associated riparian areas under current US Forest Service (USFS) management and to suggest managerial strategies with the potential to maintain or improve riverine environments. We initiated a five year study in 2008 to evaluate the use by cattle of 30 m (98.4 ft) and 60 m (196.9,ft) buffers on permanent streams on three extensive study sites in northeastern Oregon.The three study sites cover 43,972 ha (108,700 ac) within a broader region 120 km (74.5 mi) north-south by 50 km (31 mi) east-west. Ten randomly selected cows from herds grazing each site were fitted with GPS collars that recorded position, date, and time at approximately five minute intervals throughout the grazing season. Nearly 3,750,000 cow positions were collected on the allotments during the study. The relative occupancy of cattle in buffers along both sides of perennial streams were determined on an annual and monthly basis by site. Each position was tagged with the date and time of occurrence. Relative use within 30 m of the stream varied substantially from site to site (0.74% to 2.54%), month to month (0.00% to 5.21%), and year to year (0.86% to 2.13%). In some months, GPS data indicated that watering was nearly exclusive from streams. In other months, stream use was low or nil, and watering was from water developments, small springs, seeps, puddles, or other source. Cattle preferred to access streams at specific locations where streambank slope, the lack of physical obstructions, and solid footing facilitated water access.

Bangladesh has a high global hunger index with grave impacts of seasonal hunger. Short duration varieties (SDV) and direct seeding of rice (DSR) were introduced to farmers in NW Bangladesh during the monsoon season or kharif-2 to overcome seasonal hunger or monga . These technology options allow early harvest, which increased household food security and livelihood opportunities during and beyond the hunger season. The farmers who used short duration varieties and/or direct seeding were able to harvest three weeks earlier than those who used the traditional practice of long duration varieties and transplanting. More than 70 % of the SDV_DSR farmers completed harvest by mid-October, and all had done so by the end of October, whereas fewer than 5 % of farmers who grew long duration rice varieties that were transplanted, had harvested within the monga period, with most of them (80 %) harvesting during the last week of November. Early harvesting of rice generated significant, multifaceted impacts on the lives of rice farming communities in northwest Bangladesh by increasing rice production, and providing and/or increasing income along with creating additional jobs for the landless or agriculture day laborers in the lean or monga period. We estimated that during the monsoon season, the average hired labor demand was 40 person days/ha, with around 67 % of this labor generated by SDV_DSR. Further, there were improvements in access and availability of food during deficit times of the year. These technology options for rice production could be scaled out in similar agro-environments to reduce seasonal hunger and produce positive benefits on a range of factors.

Opuntia ficus-indica (L.) Mill. has been propagated for its fruits and young pads for human consumption, as well as for forage for domestic livestock for hundreds of years. Recently, it has been suggested that this plant could be beneficial in arid regions of the world where it has not been introduced. We used environmental tolerances for O. Ficus-indica gleaned from literature reviews, a rapid survey of this cactus growing in Jordan, and climatic data in a Geographic Information Systems (GIS) context to build a simple model of O. Ficus-indica suitability for Jordan. Rainfall and temperature were deemed the most important environmental variables to be employed in our model. We identified areas of the country within the range of annual rainfall between 250 and 505 mm and those with an absolute minimum temperature in any month above 1.5 degrees C. Climate data in our analysis came from the WorldClim GIS data set. We then eliminated areas with salt-affected soils. We extracted soil type, temperature and annual precipitation from the climatic GIS layers at twenty-one sites in Jordan where O. ficus-indica was found to be growing. Nineteen locations had aceptable values within the environmental tolerances for annual rainfall and temperature specified by the literature review. Two locations were drier than the recommended climatic range for the establishment of catus, and probably represent sites ameliorated by supplemental irrigation or water harvesting. A conservative figure of seven percent of Jordan's 89,342 km(2) was determined to have potential for cactus, based on aforementioned tolerances of temperature and annual rainfall. Inclusion of high-resolution soil information and digital elevation layer in the model, when they become available, would further refine the prediction of areas with potential for O. ficus-indica growth and cultivation.

Propyrisulfuron, a recently developed sulfonylurea herbicide, has shown high activity against broadleaf weeds, sedges, and grasses, unlike older sulfonylureas which are active only against broadleaf weeds and sedges. Greenhouse and laboratory studies were conducted to determine if the differential response of three rice cultivars (Azucena, N22 and IR64) and five weed species (Ludwigia hyssopifolia, Cyperus iria, Echinochloa colona, Echinochloa crus-galli, and Leptochloa chinensis) to propyrisulfuron is a function of its acetolactate synthase (ALS) activity. Growth and ALS activity were measured from test plants grown in sterilized soil under greenhouse conditions. Propyrisulfuron inhibited in vivo ALS activity of the five weed species resulting in reduced shoot fresh weight, growth inhibition and eventual death. Ludwigia hyssopifolia and Cyperus iria were most susceptible, followed by Echinochloa colona, Echinochloa crus-galli, and Leptochloa chinensis. In weeds, inhibition of ALS activity increased progressively with time, with lowest in vivo ALS activity and greatest injury at 6 days after herbicide spraying. In contrast, minimal inhibition of in vivo ALS activity was observed in the three rice cultivars, where Azucena (japonica) showed lesser tolerance than N22 (aus) and IR64 (indica). Greater seedling injury and in vivo ALS inhibition occurred in plants treated at the two-leaf stage than in plants treated at the five-leaf stage. The 150 values of in vitro ALS activity were similar in rice and weeds indicating that response to propyrisulfuron cannot be attributed to differences in ALS sensitivity at the target site. The study showed that propyrisulfuron is active not only against L. hyssopifolia and C. iria but also against E. colona, E. crus-galli and L. chinensis, with high selectivity to rice. The ability of propyrisulfuron to control grasses is a characteristic not found in older sulfonylureas. Hence, propyrisulfuron can be used as an alternative herbicide that can control grasses, broadleaf weeds and sedges in rice.

Propyrisulfuron is a new pyrimidinylsulfonylurea herbicide with a fused heterocyclic moiety. Similar to older sulfonylureas, propyrisulfuron inhibits the activity of acetolactate synthase (ALS), the enzyme involved in branched-chain amino acid synthesis. Previous studies have shown that ALS activity, and consequently, the growth of susceptible plants was inhibited when treated with propyrisulfuron. This study was conducted to determine whether or not the addition of branched chain amino acids to the growth medium will alleviate the inhibition of ALS activity and the growth of propyrisulfuron-treated rice and weeds. Visual assessment of injury, shoot height, shoot biomass, in vivo ALS activity and ALS content showed that addition of 100 mg L-1 valine, isoleucine and leucine significantly reversed ALS inhibition and resulted in recovery from ALS and growth inhibition of the propyrisulfuron-treated rice and weeds. Recovery of the weeds, which were more susceptible than rice, was more pronounced than that of rice. Addition of all three amino acids resulted in greater reversal of ALS inhibition and better recovery compared with addition of only two amino acids.

We assessed the impact of combining direct-seeded rice (DSR) and early-maturing varieties (EMVs) on productivity, costs, income and agricultural employment of farmers in two hunger-prone districts of northwest Bangladesh. Analysis included descriptive statistics, comparison of means and regression. The combination of DSR and EMV has a significant positive effect on the income of farmers by US$625 per ha from aman (wet) to boro (dry) seasons. The main reasons for the increase in income were a higher rice yield (US$669 kg/ha) and a reduction in costs (US$44 per ha) due to less labour required in crop establishment in the aman season and a higher yield and income for boro crops. Farmers were able to plant their boro crops earlier and sell their crops at a time when the supply in the market was low and prices were higher. For agricultural labourers, the early aman harvest generates more labour demand (19% in Rangpur and 22% in Nilphamari), with the assumption that 5% of the total rice area was planted using both DSR and EMVs. Direct-seeding and shorter duration rice varieties therefore enable farmers to obtain a higher yield and income while allowing agricultural workers to earn money in the monga months and ensuring efficient use of limited resources for sustainable agricultural production.

This chapter provides an overview of crop and weed management practices currently available in Africa. The need for additional options to manage weeds to augment the limited range currently available to rice farmers in Africa is also discussed.