Yield gap analysis and assessment of climate-induced yield trends of irrigated rice in selected provinces of the Philippines

This study describes a combined empirical/modeling approach to assess the possible impact of climate variability on rice production in the Philippines. We collated climate data of the last two decades (1985-2002) as well as yield statistics of six provinces of the Philippines, selected along a North-South gradient. Data from the climate information system of NASA were used as input parameters of the model ORYZA2000 to determine potential yields and, in the next steps, the yield gaps defined as the difference between potential and actual yields. Both simulated and actual yields of irrigated rice varied strongly between years. However, no climate-driven trends were apparent and the variability in actual yields showed no correlation with climatic parameters. The observed variation in simulated yields was attributable to seasonal variations in climate (dry/wet season) and to climatic differences between provinces and agro-ecological zones. The actual yield variation between provinces was not related to differences in the climatic yield potential but rather to soil and management factors. The resulting yield gap was largest in remote and infrastructurally disfavored provinces (low external input use) with a high production potential (high solar radiation and day-night temperature differences). In turn, the yield gap was lowest in central provinces with good market access but with a relatively low climatic yield potential. We conclude that neither long-term trends nor the variability of the climate can explain current rice yield trends and that agroecological, seasonal, and management effects are over-riding any possible climatic variations. On the other hand the lack of a climate-driven trend in the present situation may be superseded by ongoing climate change in the future.

Natal nest locations of the Asian house rat (Rattus tanezumi) in lowland rice–coconut cropping systems: a coconut penthouse or rice bunds with water frontage?

CONTEXT. Rattus tanezumi is a serious crop pest within the island of Luzon, Philippines. In intensive flood-irrigated rice field ecosystems of Luzon, female R. tanezumi are known to primarily nest within the tillers of ripening rice fields and along the banks of irrigation canals. The nesting habits of R. tanezumi in complex rice–coconut cropping systems are unknown. AIMS. To identify the natal nest locations of R. tanezumi females in rice–coconut systems of the Sierra Madre Biodiversity Corridor (SMBC), Luzon, during the main breeding season to develop a management strategy that specifically targets their nesting habitat. METHODS. When rice was at the booting to ripening stage, cage-traps were placed in rice fields adjacent to coconut habitat. Thirty breeding adult R. tanezumi females were fitted with radio-collars and successfully tracked to their nest sites. KEY RESULTS. Most R. tanezumi nests (66.7%) were located in coconut groves, five nests (16.7%) were located in rice fields and five nests (16.7%) were located on the rice field edge. All nests were located above ground level and seven nests were located in coconut tree crowns. The median distance of nest sites to the nearest rice field was 22.5m. Most nest site locations had good cover of ground vegetation and understorey vegetation, but low canopy cover. Only one nest location had an understorey vegetation height of less than 20 cm. CONCLUSIONS. In the coastal lowland rice–coconut cropping systems of the SMBC, female R. tanezumi showed a preference for nesting in adjacent coconut groves. This is contrary to previous studies in intensive flood-irrigated rice ecosystems of Luzon, where the species nests mainly in the banks of irrigation canals. It is important to understand rodent breeding ecology in a specific ecosystem before implementing appropriate management strategies. IMPLICATIONS. In lowland rice–coconut cropping systems, coconut groves adjacent to rice fields should be targeted for the 20 management of R. tanezumi nest sites during the main breeding season as part of an integrated ecologically based approach to rodent pest management.

Root distribution, nutrient uptake, and yield of two upland rice cultivars under two water regimes

Upland rice (Oryza sativa L.) cultivation has been increasing in global importance due to the decreasing water availability for flood- irrigated rice. The use of sprinkler irrigation to supplement rainfall and the identification of cultivars more adapted to lower water availability could be effective alternatives for producing upland rice without yield losses while using less water. The objective of this field study was to evaluate the root distribution, plant nutrition, and grain yield of two drought tolerant upland rice cultivars under two water regimes in the Cerrado Region of Brazil during two growing seasons. The main plots were two water regimes (rainfed and sprinkler-irrigation plus rainfall). Subplots were two upland rice cultivars Carajás and IAC 201. Low water availability reduced root growth by 7% and grain yields were from 2644 to 4002 kg ha-1 on average for rainfed and sprinkler irrigation treatments, respectively. Carajás had a significantly better root distribution, nutrient uptake, and higher grain yield (3732 kg ha-1) compared with IAC 201 (2914 kg ha-1) averaged over two growing seasons and water regimes. There were no treatment interactions. Our results suggest that, even when cultivars with a higher tolerance to less water availability are used, using sprinkler irrigation to augment limited rainfall during dry periods may be a viable method to increase upland rice grain yields. © 2013 by the American Society of Agronomy.

Increasing the effectiveness of the land manure after irrigated rice harvest.

Este artigo apresenta o progresso na pesquisa de cultivo mínimo em área de arroz irrigado. É investigado um método de preparo do solo com rolo-faca em áreas de várzea, que é um cilindro com lâminas paralelas usadas para incorporar a palha no solo. A técnica proporciona a antecipação do preparo da terra para a instalação de pastagem durante o inverno e com melhoria no controle de pragas e redução do tempo de preparo e consumo de combustível nas operações. Requerer-se uma menor potência de tração do que métodos convencionais empregando arados e grade.

Soil management, seed treatment and soil compaction on the sowing furrows affect grain yields of upland rice genotypes.

The water availability for flood irrigated rice (Oryza sativa L.) is decreasing worldwide. Therefore, developing technologies to allow growing rice in aerobic condition, such as a no-tillage system (NTS) can contribute to produce upland rice grains without yield losses and also in saving more water. The objective of this study was to determine the effect of soil management, seed treatment and compaction on the sowing furrow on grain yield of upland rice genotypes. We made two trials, one in an NTS and another using conventional tillage, CT (one plowing and two diskings). The field experiments were performed in the Central Region of Brazil in Cerrado soils. For each trial, the experimental design was a randomized block design in a factorial scheme, with three replications. The treatments consisted of a combination of 10 genotypes with 2 compaction pressures on the sowing furrow (25 kPa and 126kPa) and 2 types of seed treatment (with and without pesticide). Under CT, the seed treatment did not contribute to increase upland rice grain yields. However, under NTS the grain yield of some genotypes [BRS Esmeralda (from 723 to 1,766 kg ha-1), BRS Pepita (from 930 to 1,874 kg ha-1), AB072044 (from 523 to 1,579 kg ha-1), and AB072085 (from 632 to 1,636 kg ha-1) at 25 kPA soil compaction pressure, and Sertaneja (from 994 to 2,167 kg ha-1), BRS Pepita (from 1,161 to 2,100 kg ha-1), and AB072085 (from 958 to 2,213 kg ha-1), at 126 kPA soil compaction pressure] increased with the use of this practice. At CT the higher soil compaction pressure on the sowing furrow (from 25 kPa to 126 kPa) increased rice grain yield only when it was used seed treatment and the genotypes Serra Dourada (from 1,239 to 2,178 kg ha-1), Sertaneja (from 1,510 to 2,379 kg ha-1), and Cambará (from 1,877 to 2,831 kg ha-1). On the other hand, under NTS, increasing soil compaction pressure on the sowing furrow allowed for an increased rice grain yield of Serra Dourada (from 1,553 to 2,347 kg ha-1), Esmeralda (from 723 to 1,643 kg ha-1), AB072044 (from 523 to 2,040 kg ha-1), and Cambará (from 1,243 to 2,032 kg ha-1) without seed treatment and Sertaneja (from 1,385 to 2,167 kg ha-1) and AB072044 (from 1,579 to 2,356 kg ha-1) with seed treatment. In CT the most productive genotypes were AB062008 (2,714 kg ha-1) and BRSMG Caravera (2,479 kg ha-1), while at NTS were the genotypes: BRSGO Serra Dourada (2,118 kg ha-1), AB072047 (1,888 kg ha-1), AB062008 (1,823 kg ha-1), BRSMG Caravera (1,737 kg ha-1), Cambará (1,716 kg ha-1), AB072044 (1,625 kg ha-1), BRS Esmeralda (1,604 kg ha-1), and BRS Pepita (1,516 kg ha-1).

Participação do colmo principal e dos afilhos na produtividade do arroz irrigado, em função da densidade de semeadura

Entre as práticas culturais a serem consideradas na implantação da cultura do arroz destaca-se a densidade de semeadura, que deve estabelecer, em grande parte, a participação do colmo principal e dos afilhos nos componentes da produção, possibilitando a obtenção da máxima produtividade. O trabalho teve como objetivo avaliar a participação do colmo principal e dos afilhos na produtividade de grãos de arroz, cv. IAC 102, no sistema irrigado por inundação, em função da densidade de semeadura. O experimento foi desenvolvido sob túnel plástico, em Botucatu (SP), em caixas d'água de cimento amianto de 500 L, contendo Neossolo Flúvico Ta Eutrófico, com profundidade de 30 cm. O delineamento experimental foi o inteiramente casualizado, com quatro repetições. As densidades de semeadura foram: 100, 200, 300, 400, 500 e 600 sementes viáveis por m², em 4 linhas de 1 m por caixa, espaçadas com 20 cm. A elevação da densidade de semeadura diminui o afilhamento e proporciona a maior participação dos colmos principais, porém, não resultando em incremento de produtividade, devido à plasticidade das plantas de arroz, que proporciona o ajustamento dos componentes da produção.

Aplicação tardia de glyphosate e estande e desenvolvimento inicial do arroz em sistema de cultivo mínimo

O controle de plantas daninhas na cultura do arroz é ainda um problema, mesmo em cultivo mínimo, em razão do revolvimento do solo na linha de semeadura, que proporciona o reaparecimento de infestantes. Assim, objetivou-se estudar o efeito do atraso da aplicação de glyphosate sobre a formação do estande e o desenvolvimento inicial das plantas de arroz cv. IAC 102 irrigado por inundação. O experimento foi conduzido sob túnel plástico, em caixas d'água de 500 L, contendo NEOSSOLO FLÚVICO Ta Eutrófico. O delineamento experimental foi o de blocos casualizados, com quatro repetições. Os tratamentos consistiram da aplicação de glyphosate: seis horas antes da semeadura do arroz (testemunha); no início da emergência; três dias após a emergência; e seis dias após, sem e com lâmina d'água. A dose do herbicida foi de 1.920 g i.a. ha-1. Para todas as variáveis analisadas houve efeito significativo dos tratamentos; aos 42 dias após a emergência, constatou-se que a testemunha foi estatisticamente superior, na formação do estande, na altura de plantas, no comprimento de raiz e na massa seca das partes aérea e de raiz, aos demais tratamentos em que ocorreram atrasos na aplicação do glyphosate.

Rice versus fish revisited: On the integrated management of floodplain resources in Bangladesh

Disproportionately little attention has been paid to the dry season trade-off between rice and (inland capture) fish production on the floodplains of Bangladesh, compared to the same trade-off during the flood season. As the rural economy grows increasingly dominated by dry-season irrigated rice production, and floodplain land and water come under ever-increasing pressure during the dry winter months, there is an urgent need to focus attention on these dry months that are so critical to the survival and propagation of the floodplain resident fish, and to the poor people that depend on these fish for their livelihood. This article examines three important dry-season natural resource constraints to floodplain livelihoods in Bangladesh, and finds a common factor at the heart of all three: rice cultivation on lands at low and very low elevations. The article articulates the system interlinkages that bind these constraints and the long-run trend towards irrigated rice cropping on lower-lying lands, and suggests a management approach based on locally tailored strategies to arrest this trend. Apart from its direct relevance to the floodplains of Bangladesh, which support more than 100 million people, these lessons have relevance for river floodplain systems elsewhere in the developing world, notably the Mekong Delta.

Factors affecting technical efficiency of rice farmers in village reservoir irrigation systems of Sri Lanka

Given the importance of water for rice production, this study examines the factors affecting the technical efficiency (TE) of irrigated rice farmers in village irrigation systems (VIS) in Sri Lanka. Primary data were collected from 460 rice farmers in the Kurunagala District, Sri Lanka, to estimate a stochastic translog production frontier for rice production. The mean TE of rice farming in village irrigation was found to be 0.72, although 63% of rice farmers exceeded this average. The most influential factors of TE are membership of Farmer Organisations (FOs) and the participatory rate in collective actions organised by FOs. The results suggest that enhancement of co-operative arrangements of farmers by strengthening the membership of FOs is considered important for increasing TE in rice farming in VIS.

Gas emissions on rice culture and its importance on air quality

Dissertação para obtenção do Grau de Mestre em Engenharia do Ambiente Perfil Gestão de Sistemas Ambientais

Drainage, salt leaching and physico-chemical properties of irrigated man-made terrace soils in a mountain oasis of northern Oman

Little is known about the sustainability of irrigated oasis agriculture in northern Oman. The objective of this study therefore was to examine which factors allowed agricultural productivity to be apparently maintained during the two millenia of a mountain oasis’ existence. Soil moisture and physico-chemical properties were measured in a typical flood-irrigated field sown to alfalfa (Medicago sativa L.). Particle size, organic (C_org) and inorganic carbon content, pH and electrical conductivity (EC)of the soil profile were analyzed at 0.15, 0.45 and 1.00 m. Saturated hydraulic conductivity and the soil’s apparent bulk density and water potential were determined from undisturbed samples at 0.05, 0.25 and 0.60 m. During irrigation cycles of 6–9 days, volumetric water contents ranged from 30% to 13%. A tracer experiment with potassium bromide revealed that 52–56% of the irrigation water was stored in the upper 0.4 m of the soil. The rest of the water moved further down the profile, thus providing the necessary drainage to avoid the build-up of toxic salt concentrations. Due to differences in pore size, plant-available water in the topsoil amounted to 18.7% compared to 13% and 13.5% at 0.25- and 0.60-m depth, respectively. The aggregate structure in the upper 1.0 m of the profile is likely preserved by concentrations of calcium carbonate (CaCO3) from 379 to 434 mg kg^-1 and C_org from 157 to 368 mg kg^-1 soil. The data indicate that the sustainability of this irrigated landuse system is due to high water quality with low sodium but high CaCO3 concentration, the elaborate terrace structure and water management which allows adequate drainage.