Effects of Time of Second Nitrogen Application on Growth and Development of Rice Plants

Pot and field experiments were conducted to study the effect of different times of second nitrogen (N) application on growth, yield, protein content of grain and milling quality of rice (Oryza sativa L variety Seberang). Second N application was carried out at three-day intervals from 39 to 78 and 39 to 81 days after transplanting in pot and field experiments, respectively. Experimental design used was a randomized complete block design with treatments replicated three times. In the pot experiment, significantly higher yields were obtained from second N application made from late vegetative (39 days after transplanting) to late primary rachis branch differentiating stage (48 days after transplanting) and at middle stage of spike let differentiation (57 days after transplanting). Time of second N application had no significant effect on grain yield in the field but second N applied at panicle initiation stage (45 days after transplanting) resulted in the highest grain yield. In the field, second N application made from late vegetative to late primary rachis branch differentiating stage and from extine formation stage (66 days after transplanting) onwards significantly increased panicle number and percentage of filled grains, respectively

Effects of water management on nitrogen fertiliser uptake and recovery efficiency in rice

A planthouse experiment was carried out to determine the uptake and recovery efficiency of nitrogen fertilizer applied to rice varieties, MR 84 and Siam, grown under flooded, non-flooded (NF)-saturated and NF-field capacity water management conditions. The total nitrogen uptake and nitrogen fertilizer uptake of rice were higher under flooded and NF-saturated than under NF-field capacity condition irrespective of rice varieties. On average, the recovery efficiency of applied nitrogen fertilizer was 47.7, 43.2 and 30.4% under flooded, NF-saturated and NF-field capacity conditions, respectively. Recovery efficiency of applied nitrogen fertilizer was higher for MR 84 than Siam regardless of water management treatments. Recovery efficiency of nitrogen fertilizer from soil was 26.1, 26.9 and 18.5% for flooded, NF-saturated and NF-field capacity conditions, respectively. On the contrary, under NF-field capacity condition, the amount of nitrogen fertilizer losses from the plant-soil system was the highest (51.1%), followed by NF-saturated condition (29.9%) and flooded condition (26.2%)

Response of non-flooded rice to nitrogen rate

Nitrogen and water supply are important factors that influence rice growth and yield. The grain yield response to N application rate was significantly quadratic in nature irrespective of water management practices. A higher yield response to N application rate was observed under flooded as compared to non-flooded (NF)- saturated and non-flooded (NF)-field capacity conditions. The estimated N rates for maximum yield were 99, 105 and 126 kg/ha for flooded, NF-saturated and NF-field capacity conditions, respectively. The higher amount of N needed for maximum rice yield under NF-field capacity conditions was probably due to greater N losses as a result of alternate wetting and drying of soil as well as the reduced root system. However, the optimum N rate for maximum yield did not differ very much between flooded and NF-saturated conditions indicating the close similarity in N requirement under both water management practices. The dry shoot biomass response to N rate was quadratic but it was not significant under flooded and NF-saturated conditions. However, a significant quadratic response was observed for dry root biomass under flooded and NF-saturated conditions. The dry shoot and root biomass response to N rate was significantly linear under NF-field capacity conditions

Establishment of Desmodium ovalifolium on an ultisol

The effect of various scarification treatments on the germination of seeds of Desmodium ovalifolium (Prain) was studied. Following this a pot trial was conducted to evaluate the effects of lime, phosphorus and Rhizobium inaculation on the dry matter yield, nodulation and the nitrogen and phosphorus content in the plant. Mechanical scarification by abrasion with sandpaper improved germination by 30 percent. Liming up to the highest level of 1000 kg/ha significantly increased dry matter yield and nodulation. Phosphorus increased nodule number and phosphorus content in leaves and stems. Inoculation increased dry matter yield, nodulation and the levels of nitrogen and phosphorus in the leaves and stems

Effects of irrigation regime on irrigated rice

Field experiments on the effects of irrigation regime on irrigated rice production were carried out in Muda irrigation scheme (MADA) and Kemubu irrigation scheme (KADA) during off season 2004 and main season 2004/05. Five irrigation regimes were imposed on MR 220. Results showed that rice can be grown under saturated conditions without significant effect on the growth and yield when compared with rice grown under normal flooded or partially flooded conditions. However, rice growth and yield were significantly affected when rice was grown under field capacity conditions. Plants and panicles were also shorter whereas aboveground biomass at maturity and grain yield were lower when compared to rice grown under flooded or saturated conditions. Yield reduction in the range of 8–16% was observed in MADA and 40–61% in KADA for rice grown under field capacity conditions. Results from this study suggest that saturated conditions throughout the crop growth period which requires less irrigation water input than flooded conditions has high potential for the growing of direct-seeded rice under minimal water input

Rice growth and nitrogen uptake as influenced by water management

Rice (Oryza sativa L.) is grown in Malaysia mainly under flood irrigation. As water becomes increasingly scarce, demand for available water from urban and industrial sectors is likely to receive priority over irrigation. It is, therefore, necessary to adopt rice production practices that reduce water input without any adverse effects on rice growth and yield. A greenhouse study was conducted to evaluate the effects of water management practices on the growth and nitrogen (N) uptake of rice. The three water management practices studied on rice variety MR 84 and Siam were flooded, non flooded (NF)-saturated and NF field capacity. Nitrogen in the form of 15N-labelled urea (2.52% atom excess) was applied at a rate of 100 kg ha-1 in three splits. Tiller production, plant height, root growth and grain yield were adversely affected when rice was grown under NF-field capacity soil condition. Grain yield was 57.6 and 54.4% lower under NF-field capacity than flooded and NF-saturated soil condition , respectively. The lower grain yield from NF-field capacity soil resulted from few panicles, less spikelets per panicle and lower 1000-grain weight. However, maintaining soil at a NF-saturated level did not seriously affect rice growth. Rice growth, grain yield and N uptake from NF- saturated soil were comparable to rice grown under flooded condition. A lower nitrogen uptake and fertilizer N recovery under NF-field capacity were attributed to smaller root system, lower above-ground dry matter yield and greater N losses from alternate wetting and drying soil condition. These results showed that irrigated rice could be grown under reduced water input at saturated soil condition throughout the growth period without affecting growth, N uptake and yield

PGPM-induced defense-related enzymes in aerobic rice against rice leaf blast caused by Pyricularia aryzae

Rice blast caused by Pyricularia oryzae is the most devastative disease especially under aerobic cultivation systems. The bio-efficacy of plant growth-promoting microorganisms: Pseudomonas aeruginosa (UPMP1), Corynebacterium agropyri (UPMP7), Enterobacter gergoviae (UPMP9) and Bacillus amyloliquefaciens (UPMS3), Trichoderma harzianum (UPMT1) and Trichoderma virens (UPMT2) in induction of defense-related enzymes against Pyricularia oryzae was evaluated in rice cultivated under aerobic conditions. Under dual culture plate testing, all PGPMs indicated antagonism against P. oryzae with percentage inhibition radial growth (PIRG) which ranged from 51.69–81.97 %. The bio-efficacy of the respective PGPM in induction of defense-related enzymes in rice seedlings was evaluated based on individual inoculation before challenged inoculation with P. oryzae under greenhouse conditions. Inoculation of all PGPMs significantly reduced rice leaf blast severity at day eight after P. oryzae inoculation. The reduction in rice leaf blast disease severity was associated to the increase of peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) activities in rice seedlings when pre-inoculated with PGPMs. The highest leaf blast disease reduction (59.17 %) occurred with rice seedlings pre-inoculated with C. agropyri (UPMP9), followed by P. aeruginosa (UPMP1) (40.65 %), T. harzianum (UPMT1) (42.23 %), T. virens (UPMT2) (20.85 %), E. gergoviae (UPMP9) (17.84 %) and B. amyloliquefaciens (UPMS3). The high efficiency of PGPM in leaf blast disease suppression was associated with significant increase in total microbial activity (FDA hydrolysis) in rhizosphera soil (4.80–7.86 μg/g/0.5 h) compared to the control (2.25 μg/g/0.5 h). Thus, the application of PGPM is a potential alternative approach in rice leaf blast disease management of aerobic rice

Bio-efficacy of microbial-fortified rice straw compost on rice blast disease severity, growth and yield of aerobic rice

The bio-efficacy of microbial-fortified rice straw compost was evaluated for plant growth promotion, resistance induction and yield increment with Pyricularia oryzae challenged inoculation at 14, 56 and 80 days after sowing (DAS) on rice variety M4 under greenhouse conditions. Soil treatments included control (laterite soil alone), rice straw compost and rice straw compost fortified with four plant growth-promoting rhizobacteria: Pseudomonas aeruginosa (UPMP1), Corynebacterium agropyri (UPMP7), Enterobacter gergoviae (UPMP9), Bacillus amyloliquefaciens (UPMS3) and two plant growth-promoting fungi: Trichoderma harzianum (UPMT1) and Trichoderma virens (UPMT2). Soil amended with microbial-fortified rice straw compost significantly increased plant growth and productivity. Rice yield was highly correlated to productive tiller number (r = 0.96), leaf area index (LAI) (r = 0.96) and plant height (r = 0.97) for P. oryzae inoculation at 14 DAS. However, 1000 grain weight (r = 0.96), area under disease progress curve (AUDPC) (r = −0.62) and infected panicle (r = −0.59) were highly correlated to rice yield with P. oryzae inoculation at 80 DAS. Low productivity was expected with P. oryzae infection at the later growth stage. This was due to increase in panicle blast that caused deterioration of grain quality and resulting in severe yield loss (30.99 %) as compared to early infection at 14 DAS in soil amended with microbial-fortified rice straw compost. Disease development and yield loss data with different P. oryzae inoculation timings is important for disease management in rice under aerobic cultivation system

Development of microbial-fortified rice straw compost to improve plant growth, productivity, soil health, and rice blast disease management of aerobic rice

In aerobic rice cultivation systems, compost mulching and incorporation are important to rehabilitate the soil. Microbial-fortified compost is increasingly accepted as a safe approach in agro-waste management to recycling of crop residuals in agriculture soil and also to promote growth and suppress disease. This study aims to examine the stability and viability of the selected plant growth-promoting microorganisms (PGPM) in rice straw compost (RSC) over incubation period and its bio-efficacy in promoting rice (Oryza sativa) plant growth, productivity, soil health, and controlling of Pyricularia oryzae in aerobic cultivation conditions. Six selected PGPM: Pseudomonas aeruginosa (UPMP1), Corynebacterium agropyri (UPMP7), Enterobacter gergoviae (UPMP9), Bacillus amyloliquefaciens (UPMS3), Trichoderma harzianum (UPMT1), and Trichoderma virens (UPMT2) were used as a consortium of microbial inoculants to develop the microbial-fortified rice straw compost (MRSC). The MRSC was incorporated into mineral soil used for aerobic rice cultivation and its bio-efficacy was evaluated at harvest. The viability of Trichoderma spp. found stabilized at 6.78–6.00 log cfu/g and declined for all the bacterial isolates. At harvest, soil amended with MRSC significantly increased in plant height, leaf area index, 1000 grain weight, and productivity. The MRSC amended plots had significant low in rice blast disease severity with area under disease progress curve (AUDCP) of 748.22 unit/square, as compared to control (1782.67 unit/square). The physicochemical and microbiological properties of soil amended with MRSC were improved at harvest. The application of MRSC has potential to improve plant growth, productivity, rice blast disease management, and soil health of rice under aerobic cultivation systems

The effect of calcium silicate as foliar application on aerobic rice blast disease development

The bio-efficacy of calcium silicate as foliar application in enhancing physical barrier mechanism against Pyricularia oryzae in aerobic rice was investigated. A blast-partially resistant cultivar, MR219–4 and a resistant cultivar MARDI Aerob 1 were cultivated under aerobic conditions with foliar application of calcium silicate at 3, 6 and 9 mg/L. Foliar application of calcium silicate at 9 mg/L indicated the highest rice blast disease reduction for both cultivars, MR219–4 (89.21%) and MARDI Aerob 1 (97.87%). Scanning Electron Microscope (SEM) with energy dispersive X-ray (EDX) demonstrated that MARDI Aerob 1 has uniform distribution on the dumbbell shape of silica bodies in leaf epidermis compared with MR219–4 where there was a fractured on the dumbbell shape with non-uniform distribution of silica dumbbell bodies. Besides, MARDI Aerob 1 has significantly higher Silicon (Si) weight (34.49%) compared with MR219–4 (18.29%). Both rice cultivars exhibited significant increases in Si deposition for plant treated with calcium silicate through foliar application, especially when P. oryzae was inoculated. The Si content in rice leaf shown a consistence result with the Si distribution. However, the lignin content in Si-treated rice plant was significantly increased only with P. oryzae inoculation. MARDI Aerob 1 demonstrated higher lignin content (0.74%) compared with MR219–4 (0.60%) for Si-treated and P. oryzae inoculated treatment. This study revealed that foliar application of calcium silicate at 9 mg/L enhanced the resistance of aerobic rice against P. oryzae infection through accumulation and fortification of Si in the epidermal cell wall and increased lignin content in the leaf