Zinc doses, sources and application times: seed physiological potential and flooded rice yield

Abstract Zn is the most deficient micronutrient in soils worldwide and the most important and limiting micronutrient essential for rice growth and yield. It can be applied in the soil for rice cultivation or by coating seeds or leaves of plants. However, only a small amount of Zn can be applied by coating seeds or plants. We evaluated the effect of dose, source and application time of zinc (Zn) on germination, cold test (germination), seed physiological potential and flooded rice yield. The rice cultivar was Puitá INTA Cl, and the laboratory experimental design was completely randomized with a factorial 6 × 2 scheme. Six Zn doses were assessed: 0, 50, 100, 200, 400 and 800 g ha −1 , using two Zn sources such as ZnSO 4 .7H 2 O and ZnCl 2 . After treating the seeds, germination, seedling length, seedling dry matter, cold test, accelerated ageing and seedling emergence were evaluated. Seven Zn doses were used in the field: 0, 50, 100, 200, 400, 800 and 1600 g ha −1 on seeds and at the V 4 and V 11 vegetative stages. The results showed that the Zn rice seed treatment did not change germination or seedling emergence. The seedling dry mass and germination at low temperatures (cold test) are the physiological potential parameters that benefited when using ZnSO 4 .7H 2 O. Foliar application of ZnCl 2 at the V 11 vegetative stage caused leaf damage when used at a dose of 400 g ha −1 , and caused more intense damage at 1600 g ha −1 . Treating rice seeds by coating with ZnCl 2 provided 6.4% higher grain yield compared to that of ZnSO 4 .7H 2 O. Applying Zn by coating the seeds promoted 5.8% higher rice grain yield and increased grain yield 7.0% by spraying at the V 11 stage compared with that at the V 4 vegetative stage. The principal components analysis by seed treatment condition showed that the cold test and accelerated ageing had the highest contributions to the first and third components and acted in opposition to grain yield. Yield had the highest contribution to the second component and was the third component that most influenced the first and third components

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

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

Promoting black oat and ryegrass growth via Azospirillum brasilense inoculation after corn and soybean crop rotation

Inadequate management of nitrogen fertilization, due to high costs, compromises the nutrition and productivity of winter forage plants, highlighting the need to adopt sustainable alternatives, such as using nitrogen-fixing bacteria. This research evaluated the growth promotion of black oat (Avena strigosa) and ryegrass (Lolium multiflorum) plants inoculated with Azospirillum brasilense rhizobacteria. The experiments were carried out over two consecutive harvests in Santa Maria, Brazil. The sowing density was 300 viable seeds per square meter for black oats and 100 viable seeds per square meter for ryegrass. A dose of 5 ml per kg of seeds from the consortium was used as an inoculant. Following sowing, the seeds were incorporated into the soil through light harrowing. At the beginning of tillering, 50 kg of N ha-1 was applied to create treatments with and without nitrogen. Plant emergence, plant height, number of leaves and tillers were evaluated. In the first year, an inoculation response was observed for the number of black oat plants emerged m-2. In the second year (corn residue), an inoculation response was observed for the number of leaves and height of black oats. Under soybean straw for oat leaf number and ryegrass tiller number. The current research highlights the effectiveness of inoculation with Azospirillum brasilense in promoting significant improvements in the morphological components of forage crops. Following corn, an increase in the number of leaves and tillers was observed, as well as in the height of black oats. Similarly, following soybeans, there was an increase in the number of black oat tillers and the number of ryegrass leaves. The results emphasize the importance of inoculation as an effective practice to enhance crop development and performance in agricultural systems, improving sustainability and productivity under soybean and corn residues

Inoculation of soybean seeds coated with osmoprotector in diferents soil pH's

  Inoculation with nitrogen-fixing bacteria (Bradyrhizobium) is an indispensable technology to increase the productivity of the soybean crop. The objective of this study was to evaluate the viability of the inoculation with Bradyrizobium bacteria associated with the osmoprotector coating on different pre-sowing days and the effect of different soil pH on the components of yield, nodulation and grain yield of soybean. Two soybean cultivars were used, sown in two seasons and submitted to soil pH of 5.3 and 6.5. The seeds were inoculated at different pre-sowin periods with Bradyrizobium bacteria in the presence or absence of osmoprotectants. In the cultivar NA 5909RG (pH 5.3), the seeds inoculated with Bradyrhizobium and osmoprotector, at four and seven days of pre-sowing, presented an increase of 10.8% and 8.3% of productivity, in relation to those without osmoprotector. The osmoprotector and the inoculation of Bradyrhizobium increases the number and dry mass of nodules in soil with more acidic pH. The soil of lower acidity is responsible for higher grain yield, compared to the higher acidity, when both were not inoculated. The variable with the greatest explanatory power and contribution in the variability in the data of the experiment is the grain yield.

Soil tillage, rice straw and flooded irrigated rice yield

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