Evane Ferreira

Chemistry of Lowland Rice Soils and Nutrient Availability

Rice is the staple food crop for about 50% of the worlds population. It is grown mainly under two ecosystems, known as upland and lowland. Lowland rice contributes about 76% of the global rice production. The anaerobic soil environment created by flood irrigation of lowland rice brings several chemical changes in the rice rhizosphere that may influence growth and development and consequently yield. The main changes that occur in flooded or waterlogged rice soils are decreases in oxidation–reduction or redox potential and increases in iron (Fe2+) and manganese (Mn2+) concentrations because of the reductions of Fe3+ to Fe2+ and Mn4+ to Mn2+. The pH of acidic soils increased and alkaline soils decreased because of flooding. Other results are the reduction of nitrate (NO3 −) and nitrogen dioxide (NO2 −) to dinitrogen (N2) and nitrous oxide (N2O); reduction of sulfate (SO4 2−) to sulfide (S2−); reduction of carbon dioxide (CO2) to methane (CH4); improvement in the concentration and availability of phosphorus (P), calcium (Ca), magnesium (Mg), Fe, Mn, molybdenum (Mo), and silicon (Si); and decrease in concentration and availability of zinc (Zn), copper (Cu), and sulfur (S). Uptake of nitrogen (N) may increase if properly managed or applied in the reduced soil layer. The chemical changes occur because of physical reactions between the soil and water and also because of biological activities of anaerobic microorganisms. The magnitude of these chemical changes is determined by soil type, soil organic-matter content, soil fertility, cultivars, and microbial activities. The exclusion of oxygen (O2) from the flooded soils is accompanied by an increase of other gases (CO2, CH4, and H2), produced largely through processes of microbial respiration. The knowledge of the chemistry of lowland rice soils is important for fertility management and maximizing rice yield. This review discusses physical, biological, and chemical changes in flooded or lowland rice soils.

Dry Matter, Grain Yield, and Yield Components of Dry Bean as Influenced by Nitrogen Fertilization and Rhizobia

Dry bean is an important legume crop for a large portion of the worlds population. Nitrogen (N) is one of the most yield-limiting nutrients in all dry bean–producing regions of the world. A greenhouse experiment was conducted to evaluate responses of 15 dry bean genotypes to N fertilization with and without rhizobial inoculation grown on a lowland soil locally known as Varzea. Nitrogen treatments were (i) 0 mg N kg−1 (control or N0), (ii) 0 mg N kg−1 + inoculation with rhizobial strains (N1), (iii) inoculation with rhizobial strains + 50 mg N kg−1 (N2), and (vi) 200 mg N kg−1 (N3). Shoot dry weight, grain yield, yield components, maximum root length, and root dry weight were significantly affected by N fertilization, rhizobial inoculation, and genotype treatments. The N × genotypes interactions were significant for shoot dry weight, grain yield, number of pods per plant, number of grain per pod, 100-grain weight, grain harvest index (GHI), and maximum root length and root dry weight. These significant interactions indicate that genotypes performance varied with varying N rates and inoculation treatments. Maximum grain yield was produced at 200 mg N kg−1 treatment. Inoculation with rhizobial strains improved grain yield but did not reach the level of 200 mg N kg−1 applied with chemical fertilizer. Based on grain yield efficiency index, genotypes were classified as efficient, moderately efficient, and inefficient in N-use efficiency. Overall, the most efficient genotypes were BRS Pontal, Diamante Negro, BRS Grafite, BRS Requinte, and BRS 9435 Cometa, and inefficient genotypes were BRSMG Talisma and Aporé.

Biofortification of Trace Elements in Food Crops for Human Health

Micronutrient deficiencies have been reported in food crops worldwide. Several macro- and micronutrients are essential for human health. However, among these elements, the trace elements zinc (Zn), iron (Fe), iodine (I), selenium (Se), and cobalt (Co) are limiting in the diets of much of the worlds population. According to United Nations estimates, about 1 billion people, especially woman and children, are suffering from malnutrition of trace elements, especially in Africa, Asia, and South America. Improving bioavailability of these elements in food crops is an important strategy to overcome trace-element deficiencies in food crops and improving human health. Genetic variability in micronutrient contents in the grain of crops such as rice, corn, wheat, barley, soybean, and dry bean is widely reported in the literature. Hence, use of genetic variability among crop species and genotypes within species is an important strategy to achieve biofortification of grain of staple food crops. Other practices that can be adopted to improve bioavailability of essential elements in food crops are adopting appropriate agronomic practices, such as adequate rate, effective sources, and effective methods of fertilizer application. Use of biotechnology is also feasible to biofortification of staple food crops. Planting indigenous and traditional food crop species with high nutritive value is another important strategy to improve trace elements in human food.

Divergência genética de cultivares de arroz quanto à resistência a Tibraca limbativentris Stål (Hemiptera: Pentatomidae)

The genetic divergence of sixteen rice cultivars regarding their resistance to the rice stem bug, Tibraca limbativentris Stal, was estimated by multivariate analysis techniques. The experiment was carried out in greenhouse, in randomized block design with eight replications. Eight plant resistance related traits were evaluated. Genetic divergence was evaluated by multivariate procedures: generalized Mahalanobis (D2) distance, the Tochers grouping optimization method and canonical variables. The most dissimilar cultivars were Bico Ganga and Maraba Branco, while Agulha and Branco Tardao were the most similar. Five clusters were formed by the Tochers optimization method. Three canonic variables explained 88.5% of the observed variation. We concluded that the multivariate analysis techniques are suitable for analyzing the genetic divergence among rice cultivars, indicating Bico Ganga and Maraba Branco as the most promising for future breeding programs of resistance to the rice stem bug.

Growth of Tropical Legume Cover Crops as Influenced by Nitrogen Fertilization and Rhizobia

Tropical legume cover crops are important components in cropping systems because of their role in improving soil quality. Information is limited on the influence of nitrogen (N) fertilization on growth of tropical legume cover crops grown on Oxisols. A greenhouse experiment was conducted to evaluate the influence of N fertilization with or without rhizobial inoculation on growth and shoot efficiency index of 10 important tropical cover crops. Nitrogen treatment were (i) 0 mg N kg−1 (control or N0), (ii) 0 mg N kg−1 + inoculation with Bradyrhizobial strains (N1), (iii) 100 mg N kg−1 + inoculation with Bradyrhizobial strains (N2), and (iv) 200 mg N kg−1 of soil (N3). The N × cover crops interactions were significant for shoot dry weight, root dry weight, maximal root length, and specific root length, indicating that cover crop performance varied with varying N rates and inoculation treatments. Shoot dry weight is considered an important growth trait in cover crops and, overall, maximal shoot dry weight was produced at 100 mg N kg−1 + inoculation treatment. Based on shoot dry-weight efficiency index, cover crops were classified as efficient, moderately efficient, and inefficient in N-use efficiency. Overall, the efficient cover crops were lablab, gray velvet bean, jack bean, and black velvet bean and inefficient cover crops were pueraria, calopo, crotalaria, smooth crotalaria, and showy crotalaria. Pigeonpea was classified as moderately efficient in producing shoot dry weight.

Potassium-Use Efficiency in Upland Rice Genotypes

Potassium (K) uptake is greatest among essential nutrients for rice. Data related to yield, yield components, and K-use efficiency by upland rice genotypes are limited. A greenhouse experiment was conducted to evaluate influence of K on growth, yield and yield components, and K-use efficiency by upland rice genotypes. Potassium levels applied to an Oxisol were zero (natural K level) and 200 mg K kg1 of soil and 20 upland rice genotypes were evaluated. Plant height, shoot dry weight, grain yield, 1000-grain weight, and spikelet sterility were significantly affected by K and genotype treatments. Genotypes Primavera and BRA 1600 were the most efficient and genotype BRAMG Curinga was most inefficient in producing grain yield. Plant growth (plant height and shoot dry weight) and yield components (panicle number, grain harvest index, 1000-grain weight, and panicle length) were significantly and positively associated with grain yield. However, spikelet sterility was significantly and negatively correlated with grain yield.

Silicon fertilization on rice blast severity, insect pest incidence, and grain yield of irrigated rice

Rice blast and insect pests have laid a ceiling on the grain yield of irrigated rice in tropical regions. The objective of this investigation was to evaluate the effects of calcinated serpentinite and wallastonite on rice blast severity and insect pest incidence as well as grain yield of rice, in the main and ratoon crops. The effect of calcinated serpentinite and wollastonite rates (0, 1, 2, 4 and 8 Mg ha-1) on leaf blast severity were assessed on cultivar Metica 1, under greenhouse conditions. Two field experiments were conducted in the municipality of Duere, and two in Formoso do Araguaia, in the State of Tocantins. The treatments consisted of five doses of calcinated serpentinite (0, 2, 4, 6, 8 Mg ha-1) with and without fungicide application, and two genotypes BRS Formoso CNA 8502, susceptible and resistant to rice blast, respectively. The calcinated serpentinte was as much as, or more efficient than, wollastonite in reducing blast severity. It increased biomass, grain yield and percentage of endosperms without lesions caused by the rice stink bug. The application of Si contributed to sustainable management of blast and insect pest by reducing the number and doses of chemical foliar sprays, besides increasing the rice quality.

A Field technique for infesting rice with Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae) and evaluating insecticide treatments

Uma tecnica para produzir lagartas Elasmopalpus lignosellus (Zeller), no laboratorio, infestar plantas em campo e avaliar tratamentos foi descrita e testada em arroz. A acao de inseticidas para tratamento de sementes no controle da lagarta elasmo, utilizando infestacao artificial e natural, tambem foi avaliada em experimentos de tres datas de plantios. O delineamento experimental foi quadrado latino 6x6. A unidade experimental era formada de sete fileiras de arroz de 4 m de comprimento, espacadas de 0,4 m. Os tratamentos consistiram dos seguintes inseticidas e doses: tiametoxam (52,5; 70 e 105 g i.a./100 kg sementes), furatiocarbe (320 g i.a./100kg sementes), carbofuram (525 g i.a./100 kg sementes) e testemunha nao tratada. Infestacoes artificiais foram realizadas em dois grupos de tres colmos, selecionados nas fileiras bordadura das parcelas e confinados em cilindros de PVC, em tres datas de cada plantio. Colmos de cada cilindro foram infestados com tres lagartas de E. lignosellus com sete dias de idade. Imediatamente apos as infestacoes, os cilindros contendo tres colmos de arroz foram protegidos do efeito das chuvas sobre as lagartas. Os danos foram avaliados 20 dias apos as infestacoes. Infestacoes artificiais usadas neste estudo aumentaram o dano em 32 vezes, em relacao a infestacao natural das testemunhas. Inseticidas reduziram significativamente a sobrevivencia de larvas ate 60 dias apos o plantio, comparados com a testemunha.

Genotypic Differences in Dry Bean Yield and Yield Components as Influenced by Nitrogen Fertilization and Rhizobia

Dry bean (Phaseolus vulgaris L.) is an important legume worldwide and nitrogen (N) is most yield limiting nutrients. A field experiment was conducted for two consecutive years to evaluate response of 15 dry bean genotypes to nitrogen and rhizobial inoculation. The N and rhizobia treatments were (i) control (0 kg N ha−1), (ii) seed inoculation with rhizobia strains, (iii) seed inoculation with rhizobia strains + 50 kg N ha−1, and (iv) 120 kg N ha−1. Straw yield, grain yield, and yield components were significantly influenced by N and rhizobial treatments. Grain yield, straw yield, number of pods m−2, and grain harvest index were significantly influenced by year, nitrogen + rhizobium, and genotype treatments. Year × Nitrogen + rhizobium × genotype interactions were also significant for these traits. Hence, these traits varied among genotypes with the variation in year and nitrogen + rhizobium treatments. Inoculation with rhizobium alone did not produce maximum yield and fertilizer N is required in combination with inoculation. Based on grain yield efficiency index, genotypes were classified as efficient, moderately efficient, and inefficient in nitrogen use efficiency (NUE). NUE defined as grain produced per unit N applied decreased with increasing N rate. Overall, NUE was 23.17 kg grain yield kg−1 N applied at 50 kg N ha−1 and 13.33 kg grain per kg N applied at 120 kg N ha−1.