Irrigated Rice Yield Research Articles

Perception by farmers of the determinants of irrigated rice yield in Mali

Recommendations for crop management are based on agronomic diagnoses of yield determinants at plot scale usually without the farmers being involved in the evaluation process. Farmers may consequently not apply the recommendations that do not account for their own perception of yield determination. We assumed that (i) farmers have their own perceptions of yield determination; (ii) it is possible to access these perceptions through individual discussions with farmers; (iii) subsequent group discussions allow knowledge to be exchanged between farmers and a common viewpoint to be reached; (iv) agronomists can use this common viewpoint as a basis for building improved solutions in collaboration with the farmers. In this study, we used participatory methods to identify and discuss the visual references the farmers consider the crop growth as indicators to forecast the yield of their plot and the drivers they think affect these indicators. The study was conducted in two sites in the Office du Niger irrigated rice scheme in Mali and comprised three steps: (i) individual discussions with rice producers about their perception of how yield is determined, (ii) group discussions to share their individual perceptions and reach a common viewpoint, (iii) analysis of these perceptions. Seven production indicators and 29 factors that may affect these indicators were identified. The three mains indicators used by farmers were tiller abundance, hill density, and grain weight per panicle. Crop practices and constraints may prevent farmers from achieving high yields, such as a delay in the supply of fertilizers or in crop establishment. They had a complex perception of yield determination that was often close to agronomic knowledge. Here we demonstrate for the first time that farmers in the Office du Niger scheme have technical knowledge to which extension services could refer to provide relevant advice and tools for managing their constraints and improving yield.

No-tillage increases irrigated rice yield through soil quality improvement along time

No-tillage (NT) systems have arisen as a promising alternative to traditional rice cultivation in flooded soils, such as pre-germinated (PG) and conventional tillage (CT) systems. However, how NT affects soil properties and grain yield is not completely understood, especially over the long term. The objective of this study was to evaluate the long-term impact of three tillage systems (CT, NT and PG) on soil chemical, physical and biological attributes and the influence of these attributes on rice yield over time in a lowland soil of the Brazilian subtropical region. The rice grain yield was evaluated for 16 growing seasons, and the soil properties were evaluated from 17 to 21 years after the beginning of the experiment. After 14 growing seasons, rice yield was greater (3.4%) under the NT system compared to under the CT system. The increase in rice yield over time resulted in 67% greater soil organic matter (OM) content, exchangeable Ca and Mg and consequently cation exchange capacity (CEC) under the NT system compared to the CT and PG systems. In addition, soil bulk density and microbial C and N were 15%, 40% and 75% greater, respectively, under the NT system than under the CT system in the surface soil layer. The lack of soil disturbance associated with the high input of crop residues and flooding soil conditions favored the chemical, physical and biological soil properties through soil OM content, improving rice yields after 14 yr of NT adoption in relation to CT adoption.

Future changes in rice yields over the Mekong River Delta due to climate change—Alarming or alerting?

The crop simulation model Decision Support System for Agrotechnology Transfer (DSSAT) was applied over the Mekong River Delta (MRD), Southern Vietnam, to assess future (2020–2050) impacts of climate change on rice production. The DSSAT model was driven using observed station data and projected climate data derived through the dynamical downscaling of three global climate models (GCMs) using the Weather Research and Forecasting (WRF) model. The WRF model was simulated at a spatial resolution of 30 km over the study region, and the large-scale driving fields for future climates were taken from the Coupled Model Inter-Comparison Project Phase 3 (CMIP3) global models ECHAM5, CCSM3, and MIROC5 under the A2 emission scenario. Rice growth during two main seasons, namely, the winter-spring (winter) and summer-autumn (summer), were selected to quantify impacts under both irrigated and rain-fed rice cultivation. The results from this climate-crop study suggest that under rain-fed conditions, winter rice yield was likely to experience nearly 24% reduction while summer rice yield was projected to decrease by about 49%. Without irrigation, the annual rice yield was projected to decrease by about 36.5%, and under irrigated conditions, climate change is likely to reduce annual irrigated rice yields by about 1.78%. Winter rice yield was likely to decrease by 4.7% while summer rice yield was projected to marginally increase by about 0.68%. Increasing temperatures and seasonal variations of precipitation are likely to significantly reduce rice yields under rain-fed condition. In addition, (1) a decrease (increase) in the number of rainy days during the dry (wet) season and (2) positive effects of elevated CO2 for rain-fed rice growth under each of the three WRF model realizations would markedly influence rice yields. With Vietnam being one of the largest exporters of rice, these findings have serious implications for the local agricultural sector. This also serves an early warning for the policymakers and stakeholders for effective planning of not only crop production but also water resource management. The findings call for prudent diversification strategy planning by those countries which import rice.

Correlations and path analysis for yield components in irrigated rice

Grain yield of irrigated rice is a complex character resulting from the expression and association of different components, which should be considered by the breeder for an efficient process of selection of new genotypes. In this sense, the objective is to highlight the phenotypic correlations and the direct and indirect associations of the main components related to crop yield via path analysis. The experiment was carried out in an experimental field of the Lowlands Station of Embrapa Clima Temperado using six genotypes of irrigated rice: the cultivars BRS Pampa, BRS IRGA 409, BRS 7 ‘Taim’, BRS Sinuelo CL, BRS Pampeira and AB 10101 CL. The agronomic characters evaluated were grain yield, days to flowering, panicle length, panicle mass, number of fertile spikelets, number of sterile spikelets, number of tillers per plant, number of panicles per square meter, and mass of one thousand grains. The number of fertile spikelets, number of panicles per square meter, panicle mass and mass of one thousand grains influenced grain yield, both through phenotypic correlation and direct effects. In addition, there was a high direct linear tendency of these variables towards yield. Panicle length and number of sterile spikelets showed a potential of use in the indirect selection for grain yield.

Parametrization of Models and Use of Estimated Global Solar Radiation Data in the Irrigated Rice Yield Simulation

Abstract The objective of this study was to evaluate the use of estimated global solar radiation data in the simulations of potential yield of irrigated rice. Global solar radiation was estimated by four empirical models, based on air temperature, and a meteorological satellite derivated. The empirical models were calibrated and validated for 10 sites, representative of the six rice regions of the State of Rio Grande do Sul - Brazil. To evaluate the impact of the radiation estimates on irrigated rice yield simulations, the CERES-Rice model, calibrated for four cultivars, was used. The estimates of global solar radiation of the empirical models based on the air temperature showed deviations, from the observed values, of 20 to 30% and the estimated by satellite deviations of more than 30%. The global solar radiation data estimated by the Hargreaves and Samani, Donatelli and Campbell and derived satellite (PowerNasa) type air temperature-based empirical models can be used as input data in simulation models of crop growth, development and productivity of irrigated rice.

Effects of Alternate Wetting and Drying Irrigation Regime and Nitrogen Fertilizer on Yield and Nitrogen Use Efficiency of Irrigated Rice in the Sahel

The objectives of this study were to investigate water saving strategies in the paddy field and to evaluate the performance of some of the newly released rice varieties. Field experiments were conducted at Fanaye in the Senegal River Valley during two rice growing seasons in 2015. Three irrigation regimes ((i) continuous flooding, (ii) trigging irrigation at soil matric potential (SMP) of 30 kPa, (iii) trigging irrigation at SMP of 60 kPa) were tested in an irrigated lowland rice field. Irrigation regimes (ii) and (iii) are alternate wetting and drying (AWD) cycles. Four inbred rice varieties (NERICA S-21, NERICA S-44, Sahel 210 and Sahel 222) and one hybrid rice (Hybrid AR032H) were evaluated under five nitrogen fertilizer rates (0, 50, 100, 150 and 200 kg N ha−1). The results showed that rice yield varied from 0.9 to 12 t ha−1. The maximum yield of 12 t ha−1 was achieved by NERICA S-21 under AWD 30 kPa at 150 kg N ha−1. The AWD irrigation management at 30 kPa resulted in increasing rice yield, rice water use and nitrogen use efficiency and reducing the irrigation applications by 27.3% in comparison with continuous flooding. AWD30 kPa could be adopted as a water saving technology for water productivity under paddy production in the Senegal River Middle Valley. Additional research should be conducted in the upper Valley, where soils are sandier and water is less available, for the sustainability and the adoption of the irrigation water saving practices across the entire Senegal River Valley.

Simulation of growth and yield of various irrigated rice (Oryza sativa L.) genotypes by AquaCrop under different seedling ages

AbstractThe ability of AquaCrop was explored in simulating growth and development of irrigated rice genotypes under various seedling ages. Experiments were conducted in 2008 and 2009 in Amol, Iran. Local and improved cultivars were chosen (Tarom, Ghaem, and Fajr) and planted under various seedling ages. Results showed that AquaCrop simulated the rice growth and yield with reasonable accuracy. The model could follow the same order in simulated grain yield. However, the model had tendency toward slight overestimation of dry matter early in the season. AquaCrop could not capture the senescence of rice genotypes of the oldest seedling age very well and tended to keep leaves green for a longer period. The canopy cover (CC) of improved cutivars was simulated satisfactorily. Overall, it was concluded that AquaCrop is a good tool to simulate the behavior of various rice genotypes, especially improved ones, for management practices established upon seedling age variability.Recommendations for Resource Managers AquaCrop‐Rice is a practical and strong while easy‐to‐run crop simulation model that could be used successfully by extension services and farmers for decision making on their best‐management practices. AquaCrop is able to simulate successfully the effect of variability in seedling age on rice, an important management option by farmers, especially under variable starting window of the growing season in coastal regions with higher climate variability. AquaCrop can successfully capture genotypic variability in rice, which points to its capability to be used for deciding on best rice genotype in a region yielding in higher resource use efficiency.

NOTA TÉCNICA: ZONAS DE MANEJO NOS NÍVEIS DE FÓSFORO E POTÁSSIO NO SOLO E A PRODUTIVIDADE DE ARROZ IRRIGADO

O fósforo participa de processos vitais nas plantas, como a fotossíntese, a respiração, o armazenamento e transferência de energia, a divisão celular e o crescimento das células. O potássio atua na ativação de algumas enzimas e desempenha um papel importante no equilíbrio de água nas plantas. O presente trabalho teve como objetivo correlacionar os níveis de fósforo e potássio com a produtividade em arroz irrigado, bem como avaliar a viabilidade do uso de agricultura de precisão em área de arroz irrigado. O trabalho foi conduzido durante três safras em sucessão de culturas: arroz, soja, arroz, no município de Santa Vitória do Palmar/RS. Utilizou-se uma área de 22,18 ha, dividida em 15 parcelas, as quais foram georreferenciadas no ponto central. Foi coletada uma amostra de solo em cada parcela, composta por 9 subamostras, que foram encaminhadas para análises químicas. Foram gerados mapas de rendimento e de fertilidade através dos dados das análises de solo e produtividade e criadas zonas de manejo com adubação diferenciada para corrigir e uniformizar os teores de fósforo e de potássio. Os resultados deste trabalho mostram que: a agricultura de precisão proporcionou aumento de fertilidade do solo através do uso de zonas de manejo; o emprego de zonas de manejo diminuiu a variabilidade nos teores de fósforo e de potássio nas parcelas do quarteirão estudado; não houve correlação entre os níveis de fósforo e potássio no rendimento da cultura de arroz irrigado.

Influence of organic and inorganic nitrogen on the growth and yield of irrigated rice

The objective of this research was to evaluate the impact of organic and inorganic sources of nitrogen (N) on growth dynamics, yield, N content, N uptake and agronomic efficiency (AE) of irrigated rice. Four high-yielding boro (dry season irrigated) rice cultivars viz. BRRI dhan29, BRRI dhan59 Binadhan-8 and Binadhan-10 along with six N management combinations viz. Control (no N application), 140 kg N ha-1 from Prilled Urea (PU), 83 kg N ha-1 from Urea Super Granule (USG), 105 kg N ha-1 from PU + 3 t ha-1 Poultry manure, 112 kg N ha-1 from PU + 5 t ha-1 Cowdung and 77 kg N ha-1 from PU + 4 t ha-1 vermi compost were used in the study. The cultivar Binadhan-8 had a higher yield than all other cultivars because of the highest total dry matter (TDM), number of effective tillers hill-1, and number of grains panicle-1.Growth, TDM, yield, and AE were highest with 105 kg N ha-1 from PU + 3 t ha-1 Poultry manure application .The highest N uptake in grain and straw (120.1 kg ha-1 and 96.14 kg ha-1, respectively) was shown by rice cultivar Binadhan-8. In addition, significant relationships between N concentration and growth dynamics, TDM, N content, N uptake, and yield were observed. These results indicated that cultivars with the capacity to uptake more N can produce more yield and N application along with poultry manure could enhance growth, yield, AE. Therefore, the combined application of N sources in the form of PU + Poultry manure can produce good performances in terms of growth and yield of HYV rice under irrigated condition.
 Asian Australas. J. Biosci. Biotechnol. 2017, 2 (1), 9-23

Effect of irrigation and nitrogen fertilization on the agronomic traits and yield of irrigated rice

ABSTRACT Water and nitrogen management is essential to achieve high yield potential in irrigated agricultural systems. This study aimed to evaluate the influence of flood timing and nitrogen management on the agronomic performance of irrigated rice in tropical lowland. Two experiments were conducted in a Dystrophic Haplic Gleysol during the 2007/08 and 2008/09 crop years. The experiments were carried out using the cultivars BRS Jaçanã and Epagri 109. Flood timing combined with timing of topdressing 90 kg ha -1 N was evaluated at 15, 30, 45 and 60 days after emergence. The experiment was arranged in a split plot completely randomized design, flood timing in the plots and N application in the subplots, with six replications. Late flooding as well as late nitrogen application resulted in reduction of phytobiomass, grain quality and yield of irrigated rice. Flooding is recommended at the beginning of tillering for cultivar that shows higher initial growth, while for slower growth cultivar, ponding water can be established until mid-tillering. Early flooding increases sheath blight severity in rice stems. For improved quality and productive potential of irrigated rice, early flooding period and efficient sheath blight control is necessary.

EFFECT OF NITROGEN-FIXING BACTERIA ON GRAIN YIELD AND DEVELOPMENT OF FLOODED IRRIGATED RICE

ABSTRACT: This study aimed at evaluating the effect of Azospirillum brasilense, a nitrogen-fixing bacterium, on flooded irrigated rice yield. Evaluations were carried out in a shaded nursery, with seedlings grown on an Alfisol. Were performed two sets of experiments. In the first, were carried out four experiments using the flooded rice cultivars INIA Olimar, Puitá Inta-CL, Br Irga 409 and Irga 424; these trials were set up as completely randomized design in a 5x4 factorial scheme, with four replications. Treatments consisted of five nitrogen rates (0, 40, 80, 120 and 160 kg ha-1) and four levels of liquid inoculant Ab-V5 and Ab-V6 - A. brasilense (0, 1, 2 and 4 times the manufacturer's recommendation) without seed treatment. In second set, were performed two experiments using the cultivars Puitá Inta-CL and Br Irga 409, arranged in the same design, but using a 4x2 factorial. In this set, treatments were composed of four levels of Ab-V5 and Ab-V6 - A. brasilense liquid inoculant (0, 1, 2 and 4 times the recommendation of 100 mL ha-1), using rice seeds with and without insecticide and fungicide treatment. Shoot dry matter, number of panicles, and rice grain yield per pot were the assessed variables. The results showed that rice seed inoculation with A. brasilense had no effects on rice grain yield of the cultivars INIA Olimar, Puitá Inta-CL, Br Irga 409 and Irga 424.

Grain yield, water productivity and CH4 emission of irrigated rice in response to water management in south China

Reducing water input and CH4 emission while maintaining grain yield is important for the sustainable rice production in south China. However, water-saving technology has not been widely adopted by farmers because of constrains in handling, effectiveness and reliableness. Recently a simplified and easy-to-use alternate wetting and drying technology, namely “safe” AWD, has been developed and recommended to farmers in Asian countries. However, the performance of the safe AWD technology has not yet been evaluated in south China. The objective of this study was to determine whether the safe AWD technology could maintain grain yield with reduced water input and CH4 emission as compared to the conventional farmer’s practice (FP) in south China. Two on-station field experiments were conducted in Guangzhou, Guangdong province during 2014 early and late seasons. In the early season, a hybrid rice variety, Tianyou 3618 (TY3618), was arranged in a randomized complete block design with three water treatments, i.e., AWD15, AWD30 and continuous flooding (CF). In the late season, a split-plot design was employed with four water management (AWD15, AWD30, CF and FP) as main plots and two varieties as subplots. The two varieties were TY3618 and Hefengzhan (HFZ, inbred). Field water level and soil water potential were recorded daily and the CH4 emission was monitored at 7-day intervals. Crop growth, grain yield and water productivities were measured. Results showed that grain yields under AWD15 and AWD30 were comparable with CF, while water input and total CH4 emissions were significantly reduced under the two AWD treatments for both seasons. In the late season, there were no significant differences in grain yield among the four irrigation treatments for HFZ. While for TY3618, grain yield in AWD30 was significantly lower than AWD15. Irrigation water input in AWD15 and AWD30 was 19.4% and 29.7% lower, and irrigation water productivity was 31.7–37.6% and 48.4–53.2% higher than FP, respectively. Over all, no significant differences were found in maximum tiller number, leaf area index, total aboveground dry weight, among the four irrigation treatments for HFZ. While for TY3618, the crop growth rate during grain-filling stage in AWD30 was significantly lower than CF and FP. The CH4 emission under AWD15 and AWD30 were 37.4–45.7% and 61.1–77.1% lower than FP, respectively. Multi-location on-farm comparisons were conducted in north, central, and southwest region of Guangdong province and the results confirmed that AWD15 could obtain comparable grain yield as FP with fewer irrigations. These findings suggested that the AWD15 could be used for water-saving and CH4 emission mitigation while maintaining grain yield in rice production in south China. This is the first report on the performance of safe AWD in south China.

Improving Rice Productivity and Profitability with a Single Fertilizer-Management Option over Two Cropping Seasons in the Senegal River Valley

One of the main factors limiting the yield and productivity of irrigated rice in the Sahel of West Africa is the high cost of fertilizers and inefficient use of nutrients in the cropping systems. A two-year experiment was conducted over four consecutive seasons at Ndiaye (16°11'N, 16°15'W) and Fanaye (16°32'N, 15°11'W) along the Senegal River Valley to investigate alternative fertilizer management options in the double cropping system of rice. Eight fertilizer management options (FMO) were compared to the recommended seasonal application of NPK fertilizer based on yield data, the value-cost ratio (V/C) and the sustainabily of the recommendation. Rice yields increased from 2.5 t/ha without fertilizer application to 8 t/ha under the nine FMOs, which produced similar yields each season at both sites. The V/Cs of the recommended NPK fertilizer (applied each season) varied from 2.3 to 3.7. The V/Cs of FMO that supplied NPK during the hot dry season (HDS) and N during the wet season (WS), or conversely (NPK-N) varied from 3.2 to 5.7. The V/Cs of NPK-NP varied from 2.4 to 4.3. The V/Cs of NPK-NK varied from 2.4 to 4.4. The highest V/Cs ratios (5.2 to 6.3) were obtained by FMOs that supplied NP during the HDS and N during the WS, or conversely. It is concluded that when soil P-Bray1 is above 7 mg P ha-1, FMOs that supply NPK fertilizer in one season and only N fertilizer in the following season could reduce the cost of fertilization by 26% and improve rice productivity for sustainable management of the double cropping system of rice in the Senegal River Valley.

Contributions of lateral flow and groundwater to the spatio-temporal variation of irrigated rice yields and water productivity in a West-African inland valley

Water management techniques to elevate rice yields and productive use of water resources in Africa, frequently lack a substantial spatial assessment as they are often based on plot level measurements without taking into account toposequential effects present in the landscape. These effects have been shown to significantly affect spatio-temporal variations in water availability and rice productivity in Asia. Therefore, this study addresses the spatio-temporal variations of the various water components within irrigated toposequences in an African inland valley and assesses its effect on water productivity and respective rice yields for two irrigation practices: (i) continuous flooding (CF), a well-known water management practice in rice cultivation used worldwide and (ii) a reduced irrigation scheme (RI) where irrigation is applied every 5 days resulting in a 1–2cm water layer after irrigation.The lateral flow observed in the inland valley had a strong two-dimensional character, contributing to water gains between fields, located at the same toposequential level as well as along toposequences. The toposequential effect on sub-surface hydrological processes masked the overall effect of water management treatment on rice production. Additionally, the associated water productivity (WP) was not found to differ significantly between the treatments when standard calculations (i.e. net irrigation and evapotranspiration) were used but a clear toposequential effect was found for the fertilized lower lying fields when the net irrigation was corrected by the lateral flow component. Results of the established mixed regression model indicated that based on the groundwater table, rainfall and standard soil physico-chemical characteristics rice yields can be predicted in these African inland valleys under continuous flooding and reduced irrigation practices. Validation of the established regression function of inland valleys, representing various groundwater tables in the region, could lead to improved regression functions suitable to estimate spatial variation in rice production and water consumption across scales as affected by water management, fertilizer application and groundwater tables.

Water and Fertilizer Productivity in Dry Season Irrigated Rice at Farmer’s Field

Two on-farm experiments were conducted during dry seasons, 2001-04 at Kurigram and Pirgonj in Thakurgaon districts to select the best water management practices and to find out the suitable and economically viable combination of irrigation scheduling and fertilizer dose for maximizing irrigated rice yield. In alternate irrigation at saturation (AIS) treatment, about 28% water was saved compared to continuous flooding (CF), but it was needed to apply water frequently. However, alternate wetting and drying (AWD) method saved 31% and 39% water in Kurigram and Pirgonj, respectively compared to CF. In both the sites, there was no significant yield difference among the water treatments, though the applied water varied from 836-1046 mm in Kurigram and 802-1092 mm in Pirgonj. The water productivity in Kurigram ranged from 0.62 to 0.89 kg m-3, whereas in Pirgonj it varied from 0.54 to 0.75 kg m-3. Besides, AWD had the highest water productivity irrespective of locations and farmer can follow AWD practices for achieving competitive rice yield with reduced irrigation cost. The soil test based (STB) fertilizer management gave the highest grain yield followed by BRRI recommend dose irrespective of water managements. About 33-35% less amount of water was required in AWD compared to farmer’s practice (FP) in both the sites having 0.5-1.0 t ha-1 yield advantage. In both the locations, the water productivity was the highest with STB fertilizer in combination with AWD water management which required additional fertilizer cost of Tk. 2800 ha-1, but resulted in added benefit of Tk. 8400 ha-1 compared to FP. In STB fertilizer treatment, nutrient uptake was more compared to BRRI recommendation and FP. It was concluded from the study that AWD water management practice was the best option for water saving and improving water productivity. The combination of AWD with STB fertilizer management is suitable for maximum return from rice cultivation in light textured soils.DOI: http://dx.doi.org/10.3329/brj.v17i1-2.20902Bangladesh Rice j. 2013, 17(1&2): 64-74

Climate change impacts on rain-fed and irrigated rice yield in Malawi

There is extensive scientific evidence on climate impacts and adaptation in rice (Oryza sativa L.), but the majority relates to production in South Asia and China. Only a handful of studies have been conducted in Sub-Saharan Africa and none in Malawi. In this paper, the climate impacts on rain-fed and irrigated rice yield have been assessed by combining the downscaled outputs from an ensemble of general circulation models (GCM) (HADCM3, INCM3 and IPCM4) with data from the LARS-WG weather generator to drive the CERES-Rice crop model. This was calibrated and validated using 10 years (2001–2010) field data from three rice schemes to simulate the baseline (1961–1990) yield (t ha−1) and then model future yield changes for selected (B1 and A2) emissions’ scenarios for the 2050s. Although relatively small increases in average yield were projected (+8% and +5% for rain-fed and irrigated rice, respectively), there was large uncertainty (−10% to +20% yield change) when considering different GCMs and emission scenario. Farmer responses to cope with the projected impacts include both autonomous and planned adaptation strategies, such as modifying planting dates to maximize crop growth calendars and available soil moisture, increased use of on-farm water conservation measures and land levelling to improve water efficiency in rice schemes dependent on surface irrigation.

Manejo do solo, palha residual e produtividade de arroz irrigado por inundação

The objective of this study was evaluate the effect of management systems and straw in flooded irrigated rice yield. The experimental design was a completely randomized with three experiments and, 10 replications in experiment 1 and 2 and, 6 replications in experiment 3. The experiments were: E1 – no-till system (E1PD) and conventional system with two harrowings at 0.0–0.07 m layer and leveling with remaplam (E1PC), after three years of sowing rice, after fallow of rice tillage, with sowing of rye grass in winter and grazing; E2 – no-till system (E2PD) and conventional system after native field (E2PC); E3 – no-till without straw on soil surface (E30P), current straw on soil surface of 3,726 kg ha-1 (E31P), two times current straw of 7,452 kg ha-1 (E32P) and three times current straw of 11,178 kg ha-1 (E33P). In soil, were evaluated the average geometric diameter of aggregates, soil bulk density, soil porosity, macro and microporosity, in 0.0-0.05 and 0.05-0.10 m layer. In harvest were evaluated the panicles number in 0,25 m2 area, number of filled, empty an total grains in 10 panicles, mass of one thousand seeds and rice grains yield in 2 m2. The conventional system presented greater macroporosity and total porosity, compared with no-till system, however, does not result in differences in production components and rice grains yield. Soil tillage in no-till, with rice straw on soil surface up to 11,178 kg ha-1, before sowing, not reduces flooded irrigated rice grains yield.

Accumulation and utilization of nitrogen, phosphorus and potassium of irrigated rice cultivars with high productivities and high N use efficiencies

In the Jiangsu province of Southeast China, high irrigated rice yields are supported by high nitrogen (N) fertilizer inputs and low fertilizer N use efficiencies. A little attention has already been paid to the combined increase of rice yield and N use efficiency, however, the accumulation and utilization of N, phosphorus (P) and potassium (K) of irrigated rice genotypes with high yield and N use efficiency is still obscure. Field experiments were conducted in 2010 and 2011 where two cultivars with low productivity and low N use efficiency (LPLNE), two cultivars with high productivity and medium N use efficiency (HPMNE) and two cultivars with high productivity and high N use efficiency (HPHNE) were grown separately under their respective optimum N application to achieve maximum attainable yields. Accumulation and utilization of N, P and K as well as their interacting relationships were studied. The results showed that: (i) When values were averaged across cultivars and years, compared with LPLNE, HPMNE and HPHME showed 18.1, 25.3, and 9.6% higher N, P, K accumulations at maturity, respectively. The N grain production efficiency (NGPE) and K grain production efficiency (KGPE) were both higher, although P grain production efficiency (PGPE) showed no consistent tendencies; (ii) When values were averaged across cultivars and years, in comparison with HPMNE, HPHNE achieved a 1.7% lower total N accumulation, but a 6.5% higher N accumulation during the period from heading to maturity. At maturity, N accumulation in leaves increased by 3.5% and that in grains decreased by 4.0%. Total P and total K accumulation increased by 2.5% and 2.8%, respectively, which was mainly attributed to greater accumulation after panicle initiation, especially in the period from heading to maturity. At maturity, P accumulation in leaves increased by 11.5% and that in stems and grains did not differ significantly, K accumulation in stems increased by 4.2% and that in leaves and grains did not differ significantly. The N, P and K accumulation in grains at maturity did not explain the higher N use efficiency of HPHNE. This study suggested that a decrease of N accumulation before panicle initiation and increase of N, P, K accumulation during the period from heading to maturity may be helpful to combine the high yield and high N use efficiency in rice.

Correlação linear entre componentes da produção e produtividade do arroz de terras altas em sistema plantio direto

The rice is one of the main sources of the humanity’s feeding. During the agricultural year 2009/2010, in Selvíria County, Mato Grosso do Sul State, in the Brazilian Savannah, an experiment was installed with rice upland in a Dystropherric Red Latosol (Typic Acrustox) under no-tillage, irrigated by central pivot, with the purpose of selecting the best components production to explain the variability the irrigated rice yield upland. The geostatistical grid was installed, to collect the data, with 120 sampling points, in an area of 3.0 ha and and homogeneous slope of 0.055 m m-1. The medium rice yield was of the 5980 kg ha-1. For the simple lineal regressions, the number of spikelets grenades for panicle presented the best direct potential correlation with the yield rice, given for: PGO = 115,5.NEG0,770. However, for the multiple lineal regressions, the equation equação PGO = 2754,30-411,55.NEG-461,07.NEC+436,59. NET it was the one that better she came to esteem the yield rice. However, spatial, it was not possible to establish correlation between the yield rice and the components production, once none of those it presented spatial dependence in their data.

Produtividade e qualidade industrial do arroz de terras altas em função da disponibilidade hídrica e adubação

A combinação de adubações com nitrogênio e silício, em quantidades adequadas, pode aumentar a produtividade e a qualidade dos grãos de arroz. Este trabalho objetivou avaliar componentes de produção, produtividade e qualidade industrial de grãos de arroz, cultivar BRS Primavera, em função da aplicação de silício combinado com adubação nitrogenada em cobertura, em condições de sequeiro e irrigado, em Selvíria (MS). O delineamento experimental foi em blocos casualizados, em esquema de parcelas subsubdivididas, com quatro repetições. Os tratamentos foram constituídos pelos sistemas de cultivo (sequeiro e irrigação por aspersão), as subparcelas pela aplicação de silício (0 kg ha-1 e 100 kg ha-1) e as subsubparcelas por doses de nitrogênio em cobertura (0 kg ha-1, 30 kg ha-1, 60 kg ha-1 e 90 kg ha-1). A irrigação proporcionou aumento na altura da planta e produtividade de grãos, e a aplicação de silício não alterou os componentes da produção e a produtividade de grãos, nem interferiu no rendimento industrial em cultivo irrigado. O aumento das doses de N, no sistema irrigado por aspersão, incrementou a altura, número de colmos e de panículas m-2, número total de espiguetas e a produtividade de grãos, no entanto, no sistema de sequeiro, a produtividade de grãos foi reduzida.