Soil Management Systems Improve Water Use Efficiency of Rainfed Rice in the Semi-Arid Tropics of Southern Lombok,Eastern Indonesia

Abstract

Rice (Oryza sativa) grown on rainfed Vertisols in the semi-arid tropics of southern Lombok, Eastern Indonesia, is usually flooded in the short wet season, creating a considerable demand for water. However, rice crops and secondary crops frequently suffer from water stress as the soil dries after the wet season. Four systems of soil management for rice were studied at Wakan and Kawo, with average annual rainfalls of 984 mm and 1665 mm respectively. The objective was to improve water use efficiency (grain yield/m³ water consumed). The four systems were unflooded permanent raised beds with tillage (RMT) or without tillage (RNT), and flooded flat land with tillage (FMT, the conventional system, gogorancah), or without tillage (FNT). Water was kept at 0.1 m depth in the furrows (RMT, RNT) or at 0.05 m depth on flat land (FMT, FNT). Excess water was collected in a dam (embung), and used when necessary to keep the water at the desired depth. Compared with FMT, RNT reduced crop water requirement for rice by 50% at Wakan and by 44% at Kawo. Water use efficiency in RNT was increased by 90% at Wakan, and by 56% at Kawo, compared with that in FMT. There were no differences between treatments in the yield of rice at Kawo (4.5 t/ha), but at Wakan yield was better in FMT or FNT (4.2 t/ha) than RMT or RNT (2.8 t/ha). Hence, on rainfed Vertisols of Southern Lombok, rice grown on permanent raised beds, with or without tillage, could successfully replace rice grown under the conventional flooded system with tillage on flat land (gogorancah), where the rainfall is higher. The extra water saved with permanent raised beds could be used to irrigate secondary crops.     

Bed planted rice–wheat rotation at differential soil moisture regimes on soil hydro-physical properties, root growth, nitrogen uptake, and system productivity

Along with most widely practiced resources conserving technology zero-tillage wheat after rice, adoption of permanent beds for rice–wheat rotation is also gaining popularity. Since relatively a new approach particularly for dry-seeded rice and permanent beds for wheat, very little information is known about permanent beds on soil properties, nutrient (N) use efficiency, and system productivity. A field experiment was carried out in a Typic Haplustept soil of New Delhi, India to study the effect of permanent beds on soil hydro-physical properties, root growth, nitrogen uptake, and system productivity of irrigated rice–wheat rotation. Results revealed that direct-seeded rice followed by wheat on permanent beds irrigated at different soil water tensions (field capacity, 20 and 40 kPa) reflected a significant variation in soil hydro-physical properties, reduced total nitrogen uptake, contribution by different plant parts, and N use efficiency compared to wheat after flooded transplanted rice system. Rice root weight density at flowering was also significantly low at 0–15 cm depth but higher at 15–60 cm depth in dry-seeded rice on beds. System productivity of rice–wheat rotation was 25–33% lower in permanent beds compared to flooded transplanted system. For wider acceptability of permanent beds as a promising resource conserving technology, system productivity needs to be improved.     

Lodging Resistance Related to Root Traits for Mechanized Wet-Seeding of Two Super Rice Cultivars

Mechanical hill wet-seeded rice machine is beneficial for establishing and growing uniform rows of seedlings.However,there is limited knowledge regarding the effects of the establishment of furrows on growth,lodging and yield,and their relationships with root traits.In this study,field experiments were conducted during 2012 and 2013 using two super rice varieties(hybrid rice Peizataifeng and inbred rice Yuxiangyouzhan)under three furrow establishment treatments(T1,both water and seed furrows were established by the machine;T2,only seed furrows were established by the machine;and T3,neither water nor seed furrows were established by the machine).Lodging index,lodging-related traits,grain yield,above-ground dry weight and root traits were measured.The results showed that the lodging index was significantly affected by the treatments with furrows(T1 and T2).The strongest lodging resistance was detected in the mechanical hill wet-seeded rice with furrow treatment(T1)in both 2012 and 2013.Lodging resistance was strongly related to the breaking resistance.No significant difference was found in grain yield or dry weight of the mechanical hill wet-seeded rice.Therefore,the mechanical hill wet-seeded rice with furrow treatment increased rice lodging resistance,which was related to root traits.     

Wheat cropping systems and technologies in China

Chinese wheat (Triticum aestivum) production has developed rapidly during the last 57 years, largely due to improved crop management technologies and new varieties. The history of wheat planting technologies in China was reviewed, and the physiological mechanisms that allow wheat to attain high yield under these planting systems were analyzed. The use of leaf number and stage of development to indicate the optimum timing for applications of fertilizers and irrigation water, and uniform seeding at reduced seeding rates to control lodging contributed significantly to the substantial progress in wheat productivity. However, flood irrigation and tillage-based practices also resulted in serious problems, including a decline in soil fertility and quality, environmental pollution, and inefficient use of water resources. The major future challenges facing wheat production are to improve water and nutrient use efficiency. Conservation agriculture-based resource conservation technologies such as zero or reduced tillage, flat or raised bed-planting systems, and rational management of crop residues to eliminate burning in the field are among the strategies we strongly recommend for improving agricultural environments and stabilizing/increasing wheat production in China.     

Factors affecting irrigation water savings in raised beds in rice and wheat

Raised beds have been proposed for rice–wheat (RW) cropping systems in the Indo-Gangetic Plains as a means of increasing irrigation water productivity, among many other potential benefits. Field experiments were carried out in Punjab, India, during 2002–2006 to compare irrigation water use and productivity of transplanted rice and drill-sown wheat on fresh and permanent beds and conventionally tilled flats.     

Experiences with Rice Grown on Permanent Raised Beds: Effect of Crop Establishment Techniques on Water Use,Productivity, Profitability and Soil Physical Properties

In recent years, conventional rice production technologies have been leading to deterioration of soil health and declining farm profitability due to high inputs of water and labor. Conservation agriculture(CA) based resource-conserving technologies i.e. zero-tillage(ZT), raised-bed planting and direct-seeded rice(DSR) have shown promise as alternatives to conventional production technologies to overcome these problems. Present study was undertaken during 2009–2012 to establish an understanding of how permanent raised bed cropping system could be practiced to save water at the field application level to improve water productivity and also have the capability to enhance productivity, profitability and soil physical quality. The results showed that among different crop establishment techniques, conventional-tilled puddle transplanted rice(CT-TPR) required 14%-25% more water than other techniques. Compared with the CT-TPR system, zero till direct-seeded rice(ZT-DSR) consumed 6%–10% less water with almost equal system productivity and demonstrated higher water productivity. Wide raised beds saved about 15%–24% water and grain yield decrease of about 8%. Direct-seeded rice after ZT or reduced tillage or on unpuddled soil provided more net income than CT-TPR. The CTTPR system had higher bulk density and penetration resistance due to compaction caused by the repeated wet tillage in rice. The steady-state infiltration rate and soil aggregation( 0.25 mm) were higher under permanent beds and ZT and lower in the CT-TPR system. Under CT-TPR, soil aggregation was static across seasons, whereas it improved under no-till and permanent beds. Similarly, mean weight diameter of aggregates was higher under ZT and permanent beds and increased over time. The study reveals that to sustain the rice productivity, CA-based planting techniques can be more viable options. However, the long-term effects of these alternative technologies need to be studied under varying agro-ecologies in western Uttar Pradesh, India.     

Studies on Plant Population and Stand Establishment Techniques for Increasing Productivity of Rice in Dera Ismail Khan, Pakistan

Rice production in Pakistan is constraint by many factors pertaining to prevalent planting techniques. A research on the feasibility of new planting techniques (direct seeding on flat, transplanting on flat, direct seeding on ridges, transplanting on ridges and parachute planting) in transplanted and direct wet-seeded rice was undertaken at Dera Ismail Khan region of Pakistan’s North West Frontier Province during 2002 and 2003. Among the planting techniques, the best performance for the yield formation and economic evaluation was noted for transplanting on flat during both years. Chinese parachute planting technology also showed very promising results in most of the parameters. Direct seeding on ridges could not excel transplanting on flat and parachute planting during both cropping seasons. The findings concluded the feasibility of parachute planting technology along with traditional rice transplanting on flat over all other planting techniques being practiced in the area.     

Investigating early vigour in upland rice (Oryza sativa L.): Part I. Seedling growth and grain yield in competition with weeds

This paper is the first of a series that investigates whether new cropping systems with permanent raised beds (PRBs) or Flat land could be successfully used to increase farmers’ incomes from rainfed crops in Lombok in Eastern Indonesia. This paper discusses the rice phase of the cropping system. Low grain yields of dry-seeded rice (Oryza sativa) grown on Flat land on Vertisols in the rainfed region of southern Lombok, Eastern Indonesia, are probably mainly due to (a) erratic rainfall (870–1220 mm/yr), with water often limiting at sensitive growth stages, (b) consistently high temperatures (average maximum = 31 °C), and (c) low solar radiation. Farmers are therefore poor, and labour is hard and costly, as all operations are manual. Two replicated field experiments were run at Wakan (annual rainfall = 868 mm) and Kawo (1215 mm) for 3 years (2001/2002 to 2003/2004) on Vertisols in southern Lombok. Dry-seeded rice was grown in 4 treatments with or without manual tillage on (a) PRBs, 1.2 m wide, 200 mm high, separated by furrows 300 mm wide, 200 mm deep, with no rice sown in the well-graded furrows, and (b) well-graded Flat land. Excess surface water was harvested from each treatment and used for irrigation after the vegetative stage of the rice. All operations were manual. There were no differences between treatments in grain yield of rice (mean grain yield = 681 g/m²) which could be partly explained by total number of tillers/hill and mean panicle length, but not number of productive tillers/hill, plant height or weight of 1000 grains. When the data from both treatments on PRBs and from both treatments on Flat land, each year at each site were analysed, there were also no differences in grain yield of rice (g/m²). When rainfall in the wet season up to harvest was over 1000 mm (Year 2; Wakan, Kawo), or plants were water-stressed during crop establishment (Year 1; Wakan) or during grain-fill (Year 3: Kawo), there were significant differences in grain yield (g/1.5 m²) between treatments; generally the grain yield (g/1.5 m²) on PRBs with or without tillage was less than that on Flat land with or without tillage. However, when the data from both treatments on PRBs and from both treatments on Flat land, each year at each site, were analysed, the greater grain yield of dry-seeded rice on Flat land (mean yield 1 092 g/1.5 m²) than that on PRBs (mean 815 g/1.5 m²) was mainly because there were 25% more plants on Flat land. Overall when the data in the 2 outer rows and the 2 inner rows on PRBs were each combined, there was a higher number of productive tillers in the combined outer rows (mean 20.7 tillers/hill) compared with that in the combined inner rows on each PRB (mean 18.2 tillers/hill). However, there were no differences in grain yield between combined rows (mean 142 g/m row). Hence with a gap of 500 mm (the distance between the outer rows of plants on adjacent raised beds), plants did not compensate in grain yield for missing plants in furrows. This suggests that rice (a) also sown in furrows, or (b) sown in 7 rows with narrower row-spacing, or (c) sown in 6 rows with slightly wider row-spacing, and narrower gap between outer rows on adjacent beds, may further increase grain yield (g/1.5 m²) in this system of PRBs. The growth and the grain yield (y in g/m²) of rainfed rice (with rainfall on-site the only source of water for irrigation) depended mainly on the rainfall (x in mm) in the wet season up to harvest (due either to site or year) with y = 1.1x − 308; r² = 0.54; p < 0.005. However, 280 mm (i.e. 32%) of the rainfall was not directly used to produce grain (i.e. when y = 0 g/m²). Manual tillage did not affect growth and grain yield of rice (g/m²; g/1.5 m²), either on PRB or on Flat land.     

The implications of land preparation, crop establishment method and weed management on rice yield variation in the rice-wheat system in the Indo-Gangetic plains

The implications of adopting alternative seeding methods for rice and wheat establishment were examined at three geographically separate sites in the rice-wheat system of the Indo-Gangetic plains, across northern India. Rice yields in cultivated plots, established by either wet or dry seeding methods, were evaluated in comparison to yields from zero-tillage plots and under conventional transplanting methods. In the same trials, the effects of crop establishment methods in wheat were assessed both on wheat yields and rice yields. Rice crop establishment methods markedly influenced the emerging weed flora and attainable yields were measured in relation to intensity of weed management. Over four years, average rice grain yields in the absence of weed competition were greatest (6.56 t ha⁻¹) under wet seeding (sowing pre-germinated rice seed on puddled soil), and similar to those from transplanted rice (6.17 t ha⁻¹) into puddled soil, and dry seeded rice after dry soil tillage (6.15 t ha⁻¹). Lowest yields were observed from dry seeded rice sown without tillage (5.44 t ha⁻¹). Rice yield losses due to uncontrolled weed growth were least in transplanted rice (12%) but otherwise large (c. 85%) where rice had been sown to dry cultivated fields or to puddled soil, rising to 98% in dry seeded rice sown without soil tillage. Weed competition reduced multiple rice yield components, and weed biomass in wet seeded rice was six-fold greater that in rice transplanted into puddled soil and twice as much again in dry seeded rice sown either after dry tillage or without tillage. Wheat grain yields were significantly higher from crops sown into tilled soil (3.89 t ha⁻¹) than those sown without tillage (3.51 t ha⁻¹), and also were elevated (5% on average) where the soil had been dry cultivated in preparation for the previous rice crops rather than puddled. The method of wheat cultivation did not influence rice yield. Soil infiltration rates in the wheat season were least where the land had been puddled for rice (1.52 mm h⁻¹), and greater where the soil had been dry-tilled (2.63 mm h⁻¹) and greatest after zero-tillage (3.54 mm h⁻¹).These studies demonstrated at research managed sites across a wide geographic area, and on farmers’ fields, that yields of dry seeded rice sown after dry cultivation of soil were broadly comparable with those of transplanted rice, providing weed competition was absent. These results support the proposition that direct seeding of rice could provide an alternative to the conventional practice of transplanting, and help address rising costs and threats to sustainability in the rice-wheat rotation. Further, analysis of patterns of long-term rainfall data indicated that farmers reliant on monsoon rainfall could prepare fields for dry direct seeded rice some 30 days before they could prepare fields for either transplanting or seeding with pre-germinated seed. Dry, direct seeding of rice contributes a valuable component of an adaptive strategy to address monsoonal variability that also may advance the time of wheat establishment and yield. Whilst the results illustrate the robustness, feasibility and significant potential of direct seeded rice, they also highlight the critical nature of effective weed control in successful implementation of direct seeding systems for rice.     

The management of rice grown on raised beds with continuous furrow irrigation

A field experiment compared two rice (Oryza sativa L.) cropping systems: paddy or raised beds with continuous furrow irrigation; and trialled four cultivars: Starbonnet, Lemont, Amaroo and Ceysvoni, and one test line YRL39; that may vary in adaptation to growth on raised beds. The grain yield of rice ranged from 740 to 1250 g/m² and was slightly greater in paddy than on raised beds. Although there were early growth responses to fertilizer nitrogen on raised beds, the crop nitrogen content at maturity mostly exceeded 20 g/m² in both systems, so nitrogen was unlikely to have limited yield. Ceysvoni yielded best in both systems, a result of good post-anthesis growth and larger grain size, although its whole-grain mill-out percentage was poor relative to the other cultivars. Starbonnet and Lemont yielded poorly on raised beds, associated with too few tillers and too much leaf area. When grown on raised beds all cultivars experienced a delay in anthesis resulting in more tillers, leaf area and dry weight at anthesis, and probably a greater yield potential. The growth of rice after anthesis, however, was similar on raised beds and in paddy, so reductions in harvest index and grain size on raised beds were recorded. The data indicated that water supply was not a major limitation to rice growth on raised beds, but slower crop development was an issue that would affect the use of raised beds in a cropping system, especially in rice-growing areas where temperatures are too cool for optimal crop development.     

Comparison of conventional puddling and dry tillage in rice–wheat system

In many parts of Asia, rice is transplanted in puddled fields and after the harvest of this crop wheat is grown. This traditional method of growing rice may have deleterious effect on the growth of the subsequent crop in a rice–wheat cropping system. Wheat crop was planted in the same plots following a rice crop to evaluate the residual effects of various tillage treatments suitable for rice on the growth of the subsequent crop. Rice cultivar Super-basmati was grown in summer and wheat cultivar Auqab-2000 in autumn after rice. Four treatments were used to grow rice viz. transplanting in continuously flooded conditions (TRF), transplanting with intermittent flooding and drying (TRI), direct seeded using dry seeds (DSR) and direct seeded using primed seeds (DSP). Traditional puddling tillage system was followed in TRF and TRI, while for DSR and DSP, dry tillage system was followed. For convenience, the abbreviations of the rice treatments were used to indicate the same plots during the wheat crop. For the rice crop, tiller number, fertile tillers, kernel and straw yield, and harvest index were significantly better with transplanted treatments (TRI and TRF) than the direct seeded treatments. TRI also gave a yield advantage of 5% over TRF. For wheat, crop following direct seeded rice was better than transplanting. This study suggests that intermittent irrigation in the traditional puddling tillage system and DSP dry tillage system are the promising alternatives that may be opted.     

Productivity and management of rice–wheat cropping systems: issues and challenges

Rice (Oryza sativa L.) and wheat (Triticum aestivum L.) are now grown in sequence on the same land in the same year over 26 Mha of South and East Asia to meet the food demand of a rapidly expanding human population. This rice–wheat (R–W) system brings together conflicting and complementary practices. Much of the system operates at low yield because of inadequate nutrients and inappropriate water management. The challenge to research is to understand crop responses to the required combination of practices so that management systems can be devised for high and sustainable combined yield. The repeated transitions from anaerobic to aerobic to anaerobic growing conditions affect soil structure, nutrient relations, the growth of the component crops, and their associated pests and diseases. This review establishes realistic yield targets and discusses strategies and tactics to improve complementarity of the two crops by choice of cultivar, sowing time, mechanization, soil and water management, choice and combination of organic and inorganic fertilizers, management of weeds, pests and diseases, and the inclusion of other crops into the system, especially legumes. While research must attend to existing problems and improve resource-use efficiency of existing practices, the review suggests the need to look for new production strategies that might avoid existing constraints in some areas of the R–W region. In particular, soil, water and nutrient management strategies, such as reduced tillage and use of raised beds, that avoid the deleterious effects of puddling on soil structure and fertility, improve water- and nutrient-use efficiencies, and increase crop productivity, may be appropriate.     

Assessment of management of direct seeded rice production under different water conditions in Cambodia

In order to assess direct seeding of rice technology to cope with future agricultural labor shortage in Cambodia, agronomic experiments were conducted in 2005 and 2006 to compare direct seeding with transplanting under three water conditions (non-flooded, shallow flooded, and deep flooded conditions) with/without weed control by herbicides (bentazone and cyhalofop-butyl) for two Cambodian rice varieties (shorter stature and early maturity Sen Pidao, taller stature and longer maturity Phka Rumduol). Average rice yield in 2 years was lower in direct seeding (341 g m⁻²) than transplanting (404 g m⁻²), but interaction components with year, varieties, water conditions, and weed management were significant, and the attained maximum yield of direct seeding (510 and 464 g m⁻² for Phka Rumduol variety in shallow flooded condition with weeding in 2005 and 2006, respectively) was similar to that of transplanting. Plant length and dry weight of rice were reduced in non-flooded and deep flooded conditions compared with shallow flooded condition, and grain yield was the highest in shallow flooded condition. Yield advantage of Phka Rumduol over Sen Pidao increased under direct seeding, particularly under non-flooded conditions in 2005 because weed infestation was more suppressed in Phka Rumduol even without weeding. Increase in 100 g m⁻² of weed infestation prior to heading (dry weight basis) reduced about 20% of attainable yield with weed control. This study identified importance of stature and growth duration of rice varieties and presence of standing water as well as the weed control, in order to develop and extend direct seeding in the Cambodia.     

Bed planting of wheat(Triticum aestivum L.)improves nitrogen use efficiency and grain yield compared to flat planting

Conventional flat planting is commonly used for growing wheat in Pakistan and the crop is irrigated by flood irrigation, but it leads to ineffective use of applied nitrogen owing to poor aeration and leaching and volatilization losses. The practice also results in greater crop lodging, lower water use efficiency, and crusting of the soil surface. In contrast, bed planting of wheat not only saves water but improves fertilizer use efficiency and grain yield. Three years of pooled data from the present study showed that wheat planting on beds and nitrogen application at 120 kg ha-1produced 15.06% higher grain yield than flat planting at the same nitrogen rate. Similarly, 25.04%, 15.02%, 14.59%, and 29.83% higher nitrogen uptake, nitrogen use, and agronomic and recovery efficiencies, respectively, were recorded for bed compared to flat planting. Wheat planting on beds with a nitrogen application of80 kg ha-1gave a yield similar to that of flat planting with 120 kg ha-1nitrogen. However,the economic return was 29% higher in bed planting as compared to flat planting, when nitrogen was applied at 120 kg ha-1.     

水直播对寒地粳稻产量和品质性状的影响

直播稻面积在黑龙江省逐年增加,为了解水直播栽培技术对寒地粳稻产量和品质的影响,笔者对黑龙江省水直播面积最大的虎林市和抚远县进行了试验调查。结果表明,水直播对寒地粳稻穗部结构的影响因品种而异,对金禾1号的穗长、一次枝梗数和二次枝梗数影响较小,对龙粳31号的穗长、一次枝梗数和二次枝梗数影响较大;在水直播栽培条件下,金禾1号和龙粳31号的产量可达7.78 t/hm2和8.73 t/hm2,但仍极显著低于插秧栽培,这主要与水直播稻千粒重显著降低有关;金禾1号和龙粳31号的精米率、整精米率和蛋白质含量表现出水直播的低于插秧,而直链淀粉含量要高于插秧,但两种栽培方式间的差异均未达显著水平;金禾1号的垩白粒率和垩白度表现为水直播显著低于插秧,而龙粳31号的垩白粒率和垩白度在两种栽培方式间差异不显著;金禾1号和龙粳31号的食味评分两种栽培方式间的差异也未达显著水平。     

Estimation of paddy water productivity (WP) using hydrological model: an experimental study

Water productivity (WP) expresses the value or benefit derived from the use of water. A profound water productivity analysis was carried out at experimental field at Field laboratory, Centre for Water Resources, Anna University, India, for rice crop under different water regimes such as flooded (FL), alternative wet and dry (AWD) and saturated soil culture (SSC). The hydrological model soil-water-atmospheric-plant (SWAP), including detailed crop growth, i.e, WOFOST (World Food Studies) model was used to determine the required hydrological variables such as transpiration, evapotranspiration and percolation, and bio-physical variables such as dry matter and grain yield. The observed values of crop growth from the experiment were used for the calibration of crop growth model WOFOST. The water productivity values are determined using SWAP and SWAP–WOFOST. The four water productivity indicators using grain yield were determined, such as water productivity of transpiration (WP_T), evapotranspiration (WP_ET), percolation plus evapotranspiration (WP_ET+Q) and irrigation plus effective rainfall (WP_I+ER). The highest value of water productivity was observed from the flooded treatment and lowest value from the saturated soil culture in WP_T and WP_ET. This study, reveals that deep groundwater level and high temperature reduces the crop yield and water productivity significantly in the AWD and SSC treatment. This study reveals that in paddy fields 66% inflow water is recharging the groundwater. There is good agreement between SWAP and SWAP–WOFOST water productivity indicators.     

Interaction of genotype × management on vegetative growth and weed suppression of aerobic rice

Water shortage in drought-prone rice-growing areas of the world is threatening conventional irrigated rice production systems, in which rice is transplanted into fields where standing water is maintained until harvest. Aerobic rice production systems, in which rice is grown as a direct-seeded upland crop without flooding, require less water than conventional systems, but the transition to aerobic rice systems is impeded by severe weed infestation. An environmentally friendly and less labor-intensive weed control method needs to be introduced to aerobic rice farmers. A study was conducted at the International Rice Research Institute in the 2003 wet season and 2004 dry season to evaluate the effects of genotype, seeding rate, seed priming and their interactions on vegetative growth, yield and weed suppression. Three contrasting aerobic rice genotypes differing in yield and weed-suppressive ability (WSA) were grown at three seeding rates (100, 300 and 500 viable seeds m⁻²) with or without seed priming under two weed management treatments (weed-free and weedy) in a split-plot design. In 2004, the overall weed pressure was higher than in 2003, and consequently treatment effects in this year were more distinct than in 2003. No significant interactions among the experimental factors were found for crop yield, weed biomass, leaf area index, tiller number and vegetative crop biomass. Raising seeding rate from 100 to 300 viable seeds m⁻² resulted in a significant increase in yield and a decrease in weed biomass, whereas a further increase from 300 to 500 viable seeds m⁻² did not result in a further improvement in yield and weed suppression. The stronger WSA of genotype Apo than that of genotypes IR60080-46A and IRAT 216 related to a stronger competitive ability of individual plants and a faster canopy closure (0.5–6 days earlier). The WSA of weakly competitive genotypes was partially compensated for by a higher seeding rate. Seed priming, which was only evaluated in 2003, accelerated emergence by 2 days and slightly enhanced early crop growth, but had no significant effect on yield and weed suppression. The present study suggests that combining a weed-suppressive genotype with an optimum seeding rate can serve as a tool to manage weeds.     

Rice responses to soil management in a rice-based cropping system in the semi-arid tropics of southern Lombok,Eastern Indonesia

This paper is the first of a series that investigates whether new cropping systems with permanent raised beds (PRBs) or Flat land could be successfully used to increase farmers’ incomes from rainfed crops in Lombok in Eastern Indonesia. This paper discusses the rice phase of the cropping system. Low grain yields of dry-seeded rice (Oryza sativa) grown on Flat land on Vertisols in the rainfed region of southern Lombok, Eastern Indonesia, are probably mainly due to (a) erratic rainfall (870–1220 mm/yr), with water often limiting at sensitive growth stages, (b) consistently high temperatures (average maximum = 31 °C), and (c) low solar radiation. Farmers are therefore poor, and labour is hard and costly, as all operations are manual. Two replicated field experiments were run at Wakan (annual rainfall = 868 mm) and Kawo (1215 mm) for 3 years (2001/2002 to 2003/2004) on Vertisols in southern Lombok. Dry-seeded rice was grown in 4 treatments with or without manual tillage on (a) PRBs, 1.2 m wide, 200 mm high, separated by furrows 300 mm wide, 200 mm deep, with no rice sown in the well-graded furrows, and (b) well-graded Flat land. Excess surface water was harvested from each treatment and used for irrigation after the vegetative stage of the rice. All operations were manual. There were no differences between treatments in grain yield of rice (mean grain yield = 681 g/m²) which could be partly explained by total number of tillers/hill and mean panicle length, but not number of productive tillers/hill, plant height or weight of 1000 grains. When the data from both treatments on PRBs and from both treatments on Flat land, each year at each site were analysed, there were also no differences in grain yield of rice (g/m²). When rainfall in the wet season up to harvest was over 1000 mm (Year 2; Wakan, Kawo), or plants were water-stressed during crop establishment (Year 1; Wakan) or during grain-fill (Year 3: Kawo), there were significant differences in grain yield (g/1.5 m²) between treatments; generally the grain yield (g/1.5 m²) on PRBs with or without tillage was less than that on Flat land with or without tillage. However, when the data from both treatments on PRBs and from both treatments on Flat land, each year at each site, were analysed, the greater grain yield of dry-seeded rice on Flat land (mean yield 1 092 g/1.5 m²) than that on PRBs (mean 815 g/1.5 m²) was mainly because there were 25% more plants on Flat land. Overall when the data in the 2 outer rows and the 2 inner rows on PRBs were each combined, there was a higher number of productive tillers in the combined outer rows (mean 20.7 tillers/hill) compared with that in the combined inner rows on each PRB (mean 18.2 tillers/hill). However, there were no differences in grain yield between combined rows (mean 142 g/m row). Hence with a gap of 500 mm (the distance between the outer rows of plants on adjacent raised beds), plants did not compensate in grain yield for missing plants in furrows. This suggests that rice (a) also sown in furrows, or (b) sown in 7 rows with narrower row-spacing, or (c) sown in 6 rows with slightly wider row-spacing, and narrower gap between outer rows on adjacent beds, may further increase grain yield (g/1.5 m²) in this system of PRBs. The growth and the grain yield (y in g/m²) of rainfed rice (with rainfall on-site the only source of water for irrigation) depended mainly on the rainfall (x in mm) in the wet season up to harvest (due either to site or year) with y = 1.1x − 308; r² = 0.54; p < 0.005. However, 280 mm (i.e. 32%) of the rainfall was not directly used to produce grain (i.e. when y = 0 g/m²). Manual tillage did not affect growth and grain yield of rice (g/m²; g/1.5 m²), either on PRB or on Flat land.     

Evaluation of Water-Saving Rice-Winter Crop Rotation System in a Suburb of Tokyo

Abstract

Water-saving rice-winter crop rotation systems were repeated for 4 cycles from 2000 to 2004 in an urban area, Nishitokyo, Japan, to assess the effects of water-saving (i.e. non-flooded vs. flooded) on grain yield of rice (Oryza sativa L.) and chemical constituents of percolating water. The effects of pre-rice winter cropping compared with fallow on rice yield were also examined. The pre-cultivated crops were wheat (Triticum aestivum L.), italian ryegrass (Lolium multiflorum Lam.) or spinach (Spinacea oleracea L.) with their above-ground parts removed, chinese milk vetch (Astragalus sinicus L.) or rapeseed (Brassica napus L.) with their above-ground parts incorporated before rice transplanting. Neither winter cropping effects nor its interaction with water-saving were significant for rice yield, although the yield after rapeseed incorporation tended to be 9 % higher than that after fallow. In 2001, 2003 and 2004, when more than 70% of irrigation water was saved in the non-flooded trial, average yield in non-flooded trial was 58 % of flooded trial, but water productivity increased (from 0.10 to 0.16 kg m^-3). Among the 3 years, yield in non-flooded trial was highest in 2004 when the amounts of irrigation and total water supply was larger, the frequency of dry spells was the lowest, and 2 seedlings were transplanted per hill. The nitrate and nitrite concentrations in the percolating water were far below the environmental standard values by WHO. The study showed that incorporation of winter crops had no negative effects on water-saving rice production at least for the first 4 years, and that under extreme water-saving, irrigation and planting methods could minimize yield reduction.     

Evaluation of alternative tillage and crop establishment methods in a rice–wheat rotation in North Western IGP

The rice–wheat rotation covering 13.5 million ha in the Indo-Gangetic Plains is vital for food security. Its sustainability is at risk as the current production practices are inadequate resulting in high cost of cultivation and inefficient use of inputs (i.e. water, labor and energy). In a field study, we evaluated resource conserving and cost-saving alternative tillage and crop establishment options with an aim to improve system productivity and efficiency. Treatments included transplanting and direct-seeding of rice after reduced and no-tillage, followed by wheat after no-tillage. Conventional-tilled (puddled) transplanted rice followed by conventional-tilled wheat was included as a current practice. Rice yields of transplanted rice were similar irrespective of tillage/puddling. However, both dry and wet direct-seeded rice yielded 0.45–0.61 Mg ha⁻¹ lower than puddled transplanted rice. Wheat yield after no-tillage was either higher or equivalent to conventional practice. Wheat provided more economic return (US $35 ha⁻¹) than rice. No-till wheat was 6% more profitable than the conventional practice (T1). Rice transplanting with or without puddling had similar water application but dry direct-seeded rice had 10–12% lower and wet direct-seeded rice 20–24% higher. Machine labor without tillage was lower by maximum of 51 and 43% in rice and wheat, respectively. Similarly, human labor was also 9–16% lower in no-till rice compared to other practices. Two years results consistently showed $35 more net income when rice was transplanted without puddling than that of conventional practice. Direct-seeded/un-tilled rice had variable response in 2 years; US $16 more in year 1 and similar in year 2 to the puddled transplanted rice. Direct-seeded or transplanted rice after no-tillage can be more efficient and profitable alternatives to current practice (puddled transplanted rice), however, require further refinement in areas of cultivar development for no-till direct-seeding condition, nutrient, water and weed management to harness maximal potential.