Summary Water scarcity due to global warming can increase the water demand for upland rice at critical stages of crop development. However, there is little research on cultivar responses to this scenario and technologies that enhance water use efficiency (WUE). To determine the influence of water stress at and after flowering stages of drip-irrigated upland rice cultivars on physiology, yield, and WUE, a shelter experiment was conducted using a randomized block design with a split-plot arrangement of treatments. Three modern and one traditional cultivar were subjected to five irrigation managements: 100% of the field capacity considered the reference management (RM), 70 and 40% of the RM at the flowering stage, and 70 and 40% of the RM at the grain-filling stage. In general, the modern cultivars tended to maintain higher photosynthetic rate, stomatal conductance, transpiration, leaf water potential, and lower crop water stress index compared to the traditional cultivar under water stress. The WUE decreased for all cultivars under severe stress, averaging 0.55 and 0.62 kg m−3 when stress occurred at flowering and grain-filling, respectively, whereas moderate stress imposed at grain-filling maintained WUE for all cultivars, averaging 1.21 kg m−3. In addition, grain yield (GY) showed a similar variation trend under drought stress as WUE, and its reduction was mainly associated with low filled grain percentage. Among the five irrigation treatments, both GY and WUE were the highest in the RM; the best cultivar recorded 9.3 Mg ha−1 and 1.62 kg m−3, respectively. Findings suggest that attending to the full water demand under precision drip irrigation and appropriate cultivar selection can enhance upland rice production at significant levels.

AGRONOMIA-CIêNCIA dO SOlO Fuentes alternativas de fósforo en suelos del "cerrado" cultivados con maíz (Zea mays) Alternative sources of phosphorus in "savannah" soil cultivated with maize (Zea mays

Nitrogen (N) is the most important nutrient in crop productivity and silicon (Si) increases the uptake of nutrients and affect the uptake of N. The objective of this study was to evaluate the effect of Si combined with rates of N on the growth, root development, uptake of N and Si, assimilation of N, and photosynthesis of the tomato plants (Solanum lycopersicum). A factorial 3 × 3 was used, with rates of Si 0 (control treatment), 1, and 3 mmol L–1, and rates of N 5 (control treatment), 15, and 25 mmol L–1 in the nutrient solution. The rates of N did not affect the dry mass production and uptake of Si. However, the application of Si improved the plant growth and accumulation of Si and N. Relating to control treatment, the rate of Si 1 mmol L–1 increases the dry mass production and accumulation of Si and N in order of 52, 37, and 54 %, respectively. Although the rate of N did not increase the plant growth, it was verified that the N 15 mmol L–1 improves the concentration and accumulation of N in the shoots, and the relative concentration of chlorophyll with values of 43.5, 67, and 14 %, respectively, compared to the control. The supply of Si under low and high availability of N improved the glutamine synthetase, but at the rate of N 25 mmol L–1, a decrease in the transpiration rate and stomatal conductance was verified. Under the high availability of N, the glutamine synthetase raised 78 % as an effect of Si 3 mmol L–1 compared to control treatment (Si 0 mmol L–1). Nevertheless, the transpiration rate and stomatal conductance decreased 49 and 52 % under that condition. The excess of N 25 mmol L–1 negatively affected the root development, but under that condition, the application of Si increased the root length, root surface, and root hood in order of 70, 40, and 77 % compared to the control treatment. Application of Si is recommended for tomato growth, especially when cultivated with high N availability. The application of silicon enhances the plant growth, root development, nutrient uptake, nitrogen assimilation, and photosynthesis of the tomato plants cultivated under rates of N. We recommend the use of Si 3 mmol L–1 and N 15 mmol L–1 for the tomato plants under the nutrient solution

The objective of this study was to evaluate the efficiency of glauconitic siltstone as a multi-nutrient source for flooded rice. Two experiments were carried out under greenhouse conditions, one using a Ferralsol and the another an Arenosol. Glauconitic siltstone was applied in different doses (0, 5, 20, 40, and 80 mg dm-3 K2O) and potassium chloride, wollastonite, and manganese sulfate were respectively used as standard sources, at doses of 80 mg dm-3 K2O, 270 mg dm-3 Si, and 2 mg dm-3 Mn. The sources were incubated for 90 days on the two soil types and, after the incubation period, rice plants were sown, and two consecutive rice growths were performed. The application of glauconitic siltstone in tropical soils promotes increases in the plant and grain dry matter of rice plants, as well as K, Si and Mn contents in soil samples and accumulated in plants. Greater effects following the application of glauconitic siltstone are obtained after the second rice growth due to its gradual release.

ARRIETA, RAFAEL GÓMEZ. Reactivity and agronomic efficiency of Verdete and fine-grained calcined Verdete as a multinutrient fertilizer in flooded rice. (2017). 105 f. Dissertation