Dynamics of Weedy Rice Soil Seedbank Under Differing Control Strategies in Italian Rice Fields: survey and model study

The abundance of weedy rice (Oryza sativa L.) in the soil seedbank was estimated in 2011 in Italian rice (Oryza sativa L.) fields with different histories of IMI-resistant Clearfield® rice varieties (CL), non-Clearfield® varieties (NCL) and planting methods. A model was used to predict weedy rice seedbank dynamics over time under different control strategies. Soil samples were taken from 50 rice fields cultivated with CL varieties consecutively for 0, 1, 2, or 3 years and weedy rice seedbank data were used in a model considering eight scenarios: A) rice monoculture with CL and NCL varieties in alternate years; B) two years of CL, followed by one year with NCL; C) three years of CL followed by one year of NCL; D) rice monoculture with only CL; E) rice monoculture with only NCL; F) two years of CL followed by one year of rotation with another crop (CR), and then by an additional year with NCL; G) one year of CR followed by two years of CL, and then by one year of NCL; H) two years of CR followed by two years of CL. Weedy rice seedbank exceeded 1,000 seeds m−2 in the surveyed fields with no significant differences between rice planting methods. Highest densities were found in fields cultivated for one year with CL varieties. Simulations indicated that where CL varieties were used in rice monoculture susceptible weedy rice seedbank reduced gradually, allowing a depletion after 17, 13, 11, and 9 years in scenarios A), B), C), and D), respectively. The weedy rice seedbank increased in NCL monoculture (E) and declined significantly in crop rotation scenarios (F, G, H). The simulations indicated that the introduction of crop rotation is crucial for obtaining a relatively fast reduction of weedy rice seedbank and delaying the evolution of herbicide-resistant populations.

Plant-mediated rhizospheric interactions in rice-water spinach intercropping enhance Si uptake by rice

Aims Although biodiversity utilization in paddy fields has increased in recent years, silicon (Si) nutrition of rice in intercropping systems is poorly understood. On the basis of our previous study, the present research focused on deciphering the underlying mechanisms involved in rice and water spinach intercropping, which enhance Si uptake by rice.Methods We carried out a series of experiments including field, greenhouse, and incubation experiments to explore the underlying mechanisms.Results The field trials showed that rice-water spinach intercropping with different row ratios can increase Si concentration by 9.8%-52.6% and Si absorption by 34.7%-127.8% in rice leaves at ripening stage compared to rice monoculture. The pot trials further indicated that intercropping can promote rice to increase Si concentration in Si-deficient soil, with an increase of 35.9% in stems and 29.7% in leaves, and intercropping significantly increased soil water-soluble Si content by 168.1% compared to rice monoculture. Further research indicated that there was an interaction between rice roots and water spinach roots under intercropping conditions, which not only induced the up-regulated expression of Si transporter genes in rice roots (OsLsi1, OsLsi2) and stems (OsLsi6), but also stimulated rice roots to secrete more organic acids to increase Si availability in the soil. Moreover, water spinach root exudates helped the mobilization of Si in soil through proton efflux of roots. Conclusions Rice-water spinach intercropping can greatly enhance Si absorption of rice through several beneficial ways, which will have important practical significance for sustainable rice production, especially in Si-deficient soils.

Soil bacterial community composition in rice–fish integrated farming systems with different planting years

The high productivity and efficient nutrient utilization in rice–fish integrated farming system are well reported. However, the characteristics of soil bacterial communities and their relationship with soil nutrient availability in rice–fish field remain unclear. In this study, we selected three paddy fields, including a rice monoculture field and two rice–fish fields with different planting years, to investigate the soil bacterial community composition with Illumina MiSeq sequencing technology. The results indicated that the soil properties were significantly different among different rice farming systems. The soil bacterial community composition in the rice–fish field was significantly different from that in the rice monoculture field. Five of the top 15 phyla were observed with significant differences and Nitrospirae was the most significant one. However, no taxa observed with significance between the rice planting area and aquaculture area no matter in the 1st or 5th year of rice–fish field. RDA analysis showed that the soil bacterial community differentiation in the 5th year of rice–fish field was positively correlated with soil properties, such as AN and OM contents, EC and pH value. Although the rice yields in rice–fish field decreased, the net economic benefit of the rice–fish system enhanced obviously due to the high value of aquaculture animals.

Incidence of Cereal Cyst Nematode Prevailing in Wheat-rice Growing Regions of Punjab Province, Pakistan

Background: Cereal Cyst Nematodes (CCN) are prevailing in all type of agricultural lands and responsible for enormous losses of cereal crops. The understandings on population densities and management of these nematode are required to improve crop health and productivity.Methods: A study was designed to assess the incidence of cereal cyst nematodes in wheat and rice monoculture cropping regions of eight districts of Punjab province, viz., Jhang, Khushab, layyah, Hafizabad, Sheikhupura, Narowal, Gujranwala and Sargodha in Pakistan. Population densities of cereal cyst nematodes were studied by extracting the cysts and second stage juveniles from soil samples and identified the nematode species. Result: The CCNs were found in 80% of the total 250 samples collected from wheat and rice monoculture fields of at least one crop. In the soil samples collected from wheat fields, an average of 7 to 38 cysts/100g of dry soil with eggs and J2 population of 142-771 were recorded. Whereas from the soil samples of rice fields, 17 to 25 cysts/100g soil were found with 345 to 508 eggs and juveniles. Among the wheat fields, the lowest incidence of 5.5% was recorded in kot–momin and highest incidence of 16.88% was recorded in Silanwali tehsils of Sargodha region. In rice fields, 24.69 to 27.00% incidence of CCNs was noticed in soil samples of various surveyed regions. Three different species of Heterodera genus were morphologically identified from the collections. The species includes Heterodera oryzae, Heterodera avenae and Heterodera graminophila. H. oryzae was more abundant in rice growing regions while H. avenae and H. graminophila were present dominantly in wheat growing regions. This study provides an inclusive information regarding cereal cyst nematode densities and species in wheat-rice growing regions of Punjab province of Pakistan.

Efisiensi Penggunaan Pupuk pada Sistem Pertanian Terpadu Minapadi

Rice-fish farming is a model that is considered suitable to be applied in rice fields, both on a large or limited land as long as water availability is sufficient for rice and fish to grow. In rice-fish farming, there is integration between fisheries and agriculture where integration can improve the efficiency of the supply and use of fertilizer and feed. The research aimed to find the reduction of inorganic fertilizer in integrated rice-fish farming with the rice-fish system to increase fertilizer efficiency. The experiment used a single factor randomized block design with five levels of treatment, which are; rice monoculture with 100% inorganic fertilizer, fish monoculture, rice-fish farming with 100% inorganic fertilizer, rice-fish farming with 60% inorganic fertilizer, and rice-fish farming with 20% inorganic fertilizer. Rice-fish farming could reduce the application of inorganic fertilizers through complementary relationships between rice and fish. Applying inorganic fertilizer 20% of the reference dose in the rice-fish farming produced productivity that was not significantly different from the rice-fish farming fertilized with 60% and 100% of the reference dose, and the rice monoculture with 100% of the reference dose of inorganic fertilizer. Rice-fish farming could save 80% of inorganic fertilizers so that increasing the efficiency of using inorganic fertilizers. Fish survival and fish weight in rice-fish farming were not significantly different from fish monoculture. Keywords: inorganic fertilizer, monoculture, productivity, soil nutrients

Relative Competitiveness Between Cultivated and Weedy Rice under Full and Low Light

ABSTRACT: Cultivated and weedy rice biotypes exhibit morphophysiological variations under low light, affecting competition between plants. The aim of this study was to assess relative competitiveness between cultivated and weedy rice under full and low light. Three experiments were conducted in a greenhouse, using a completely randomized design with four repetitions. The treatments in the experiment I were arranged in additive series while in the experiments II and III treatments were arranged in replacement series. Experiments II and III were carried out concomitantly to assess coexistence between the rice cultivar and weedy rice. The treatments consisted of different plants proportions: 100:0 (cultivated rice monoculture), 75:25, 50:50, 25:75 and 0:100 (weedy rice monoculture), keeping the total plant population obtained in experiment I (240 plants m-2) constant. Experiment II was conducted with full solar radiation and III under 50% light. The variables analyzed were shoot dry weight and plant height, 35 days after emergence (DAE). Competition among plants was evaluated via graphs and by interpreting competition indices. Concerning shoot dry weight, mutual losses were recorded between competitors, whereas equal competition for resources was observed for plant height. Weedy rice was more competitive than cultivated rice regardless of the light environment assessed, indicating the need for integrated methods to control this weed.

Evaluation of Mungbean Varieties for Northwest Cambodian Lowland Rice Systems

Small-scale agriculture is the economic, social and cultural foundation of Cambodian rural communities. Crop diversification is not widespread in these traditionally rice-producing smallholder farms. Rice monoculture has led to a decline in farm productivity and farming household income. Mungbean is emerging as a high-value opportunity for crop diversification in smallholder farms in north-west Cambodia. However, its expansion is being constrained by the low quality of varieties available to farmers. This study aims to evaluate the locally available varieties with others from Cambodia and the region by comparing the varieties’ agronomic and economic characteristics. The varieties from Cambodia, CMB-3 and CARDI-Chey, had superior agronomic and quality characteristics compared with the varieties available to farmers. This was reflected in the price estimate and income of both varieties which had the highest gross margins. Hence, the varieties currently available to farmers are unsuitable for continued cultivation in the modern mungbean production environment.