Conselho Nacional de Desenvolvimento Científico e Tecnológico / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Na agricultura moderna, apesar de serem empregadas as mais modernas tecnologias de cultivo de plantas e apesar dos progressos que têm sido feitos em programas de melhoramento, o máximo potencial das culturas de interesse agronômico está ainda longe de ser plenamente explorado. Assim, os bioestimulantes – uma categoria de produtos relativamente novos de diversas formulações, os quais afetam positivamente processos vitais de uma planta e apresentam grande potencial para uso na agricultura brasileira – podem ser uma alternativa promissora para os orizicultores. O objetivo deste trabalho foi conceituar e discutir o uso de agroquímicos de regulação hormonal e avaliar a influência de duas fontes bioestimulantes de aplicação foliar com Tecnologia AZAL5 (extrato de Ascophyllum nodosum) contendo silicato de potássio e micronutrientes, em aspectos nutricionais e vegetativos, na cultura do arroz de sequeiro. O primeiro capítulo teve a finalidade de, a partir de uma revisão bibliográfica, discutir o uso, os conceitos, os percalços e os benefícios de bioestimulantes, biorreguladores, bioativadores, ácidos húmicos e fúlvicos, bem como extrato de algas na agricultura brasileira. Os capítulos seguintes consistiram de dois experimentos (testes biológicos) em que foram avaliadas as duas fontes bioestimulantes – uma contendo silicato de potássio + molibdênio (Capítulo 2) e outra contendo silicato de potássio + zinco (Capítulo 3) – aplicadas via foliar na cultura do arroz. Os experimentos foram realizados em casa de vegetação, em vasos de 5 kg, com solo classificado como Neossolo Quartzarênico, utilizando-se a cultivar BRS Primavera. O delineamento experimental foi inteiramente casualizado, com quatro repetições, em arranjo 5 x 2. Os tratamentos consistiram de cinco doses (0; 1,50; 3,00; 4,50; 6,00 L ha-1), em dois modos de aplicação (parcelado e não parcelado). Foram avaliados: teores de clorofilas A, B e Total; teores foliares de silício e macro e micronutrientes; massa de matéria seca de raiz e parte aérea. Foram testadas as pressuposições estatísticas dos dados obtidos com os testes de normalidade de Kolmogorov-Smirnov e de homogeneidade das variâncias de Levene, ambos a 0,01 de significância e submetidos à análise de variância pelo teste de Tukey a 0,05 de significância. Os dados significativos para o fator quantitativo (doses) foram submetidos à análise de regressão. A aplicação da fonte bioestimulante contendo silicato de potássio + molibdênio alterou os teores foliares de K, Ca, S, Zn, Cu e a produção de massa de matéria seca de raiz; porém, não houve alteração nos teores foliares de N, P, Mg, Fe, Mn e Si, nos teores das clorofilas A, B e Total aos 55 DAE e na produção de massa de matéria seca da parte aérea em função das diferentes doses da fonte bioestimulante e dos diferentes modos de aplicação. A aplicação da fonte bioestimulante contendo silicato de potássio + zinco alterou os teores foliares de N, Ca, Mg, S, Zn e Cu e a produção de massa de matéria seca de raiz; contudo, não houve alteração nos teores foliares de Si, P, K, Fe e Mn, na produção de massa de matéria seca de parte aérea e nos teores das clorofilas A, B e Total aos 55 DAE em função das diferentes doses da fonte bioestimulante e dos diferentes modos de aplicação. / Despite the use of the most modern technologies of plant cultivation and the progress in breeding programs, the full potential of crops of agronomic interest is still far from being fully exploited. Biostimulants, a relatively new product category of various formulations, positively affect vital processes of plants and have shown great potential for use in the Brazilian agriculture, especially in the rice agriculture. The aim of this study is to discuss the use of hormonal regulation agrochemicals and assess the agronomic and nutritional efficiency of the foliar application of two biostimulants based on AZAL5 Technology (extract of Ascophyllum nodosum) containing potassium silicate and micronutrients. Chapter 1 draws on a review of the literature to discuss uses, concepts, benefits of and obstacles to biostimulants, bioregulators, bio-activators, humic and fulvic acids, as well as seaweed extract in the Brazilian agriculture. The following chapters report on two experiments (biological testing) that assessed both biostimulants – one containing potassium silicate + molybdenum (Chapter 2) and the other containing potassium silicate + zinc (Chapter 3) – applied to upland rice foliage. The experiments were carried out in a greenhouse, using 5-kg vases with Quartzipsamment soil and BRS Primavera cultivar. The experimental design was completely randomized, with four repetitions in a 5 x 2 structure. The treatments consisted of five doses (0; 1.50; 3.00; 4.50; 6.00 L ha-1) used in two modes of application (single application or in portions). The following parameters were evaluated: concentrations of chlorophyll A, B and Total; leaf content of macro and micronutrients and Si; and dry matter of root and aerial part. Statistical assumptions were assessed for the obtained data using Kolmogorov-Smirnov normality test and Levene’s test for homogeneity of variances, both set at 1%. Tukey’s test was used for analysis of variance and set at 5% significance. The significant data for the quantitative factor (doses) were included in a regression analysis. The application of biostimulant containing potassium silicate + molybdenum significantly changed the leaf content of K, Ca, S, Zn and Cu, as well as the production of dry matter of root. However, the leaf content of N, P, Mg, Fe, Mn and Si, the concentrations of chlorophyll A, B and Total, and the production of dry matter of aerial part were not significantly influenced by the different doses of said biostimulant and modes of application. The application of biostimulant containing potassium silicate + zinc significantly impacted on the leaf content of N, Ca, Mg, S, Zn and Cu, and on the production of dry matter of root. However, the leaf content of Si, P, K, Fe, and Mn, the production of dry matter of aerial part and the concentrations of chlorophyll A, B and Total were not significantly influenced by the different doses of said biostimulant applied in different modes. / Dissertação (Mestrado)

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An injection technique, in which undisturbed soil cores are labelled with ³²P to study dissolution of phosphate fertilisers in the soil, was evaluated in field and glasshouse trials. When ³²P was injected between 0-150 mm depths of the undisturbed soil columns and fertilisers applied at the surface, the amounts of fertiliser P dissolved, as measured by the increases in the exchangeable P pools, were overestimated. Three possible reasons were suggested: (i) the interaction between surface-applied fertiliser, ³²P injected through the whole soil column, and the vertical decline in root density, (ii) the decline of specific activity in the exchangeable P pool due to losses of ³²P to nonexchangeable P pools and continuous addition of P from fertiliser dissolution, and (iii) non-uniform distribution of ³²P vis-a-vis ³¹P phosphate. The injection technique may be employed to assess the effectiveness of phosphate fertilisers by introducing a concept, the fertiliser equivalent (FE). The FE is a measure of the amounts of soil exchangeable P that the fertilisers are equivalent to in supplying P to plants, when applied at the specific location. Soluble single superphosphate (SSP) applied at the surface of undisturbed grassland soil cores (Tekapo fine sandy loam), was much more effective than surface-applied unground North Carolina phosphate rock (NCPR) and 30% acidulated NCPR with phosphoric acid (NCPAPR) within the 56 day period of plant growth. An isotopic dilution method, based on tracer kinetic theory, was developed to study the rates of dissolution (F in) and retention (F out) of phosphate fertilisers in the soil in growth chamber experiments. The estimation of F in and F out required labelling of the soils with carrier-free ³²P and determination of the corresponding values of the specific activities of the exchangeable P pools, SA₁ and SA₂, and the sizes of the exchangeable P pools, Q₁ and Q₂, at times t₁ and t₂. Most of the phosphate in the monocalcium phosphate (MCP) solution entered the exchangeable P pool immediately after addition to the soils (Tekapo fine sandy loam and Craigieburn silt loam), and there was little further phosphate input. With increasing periods of incubation, the phosphate was quickly transformed to less rapidly exchangeable forms. In the soils treated with ground North Carolina phosphate rock (<150 µm, NCPR) or partially acidulated (30%) NCPR with phosphoric acid (NCPAPR), the initial exchangeable P pools were not as large as those in the soils treated with MCP, but were maintained at relatively stable concentrations for extended periods, due to the continuous dissolution of PR materials and to lower rates of pretention. An increase in P-retention caused a slight rise in the rate of PR dissolution, but also a rise in the rate of P-retention by the soil. The rate of dissolution was higher at a lower application rate in relative terms, but smaller in absolute terms. The trends in the changes of plant-available P in the soils, measured by the water extractable P, Bray I P and Olsen P, correspond to those predicted by the F in and F out values. The average rates of dissolution between 1-50 and 50-111 days estimated by the F in, however, were higher than those estimated by extractions with 0.5 M NaOH followed by 1 M HCl, and with 0.5 M BaCl₂/TEA. This is partly because the Fin values reflect a plant growth effect on PR dissolution. The relative agronomic effectiveness of NCPR and NCPAPR with respect to MCP was higher after 50 and 111 days of incubation than after 1 day. The F in values were included in all the two-variable models constructed by stepwise regression to describe the relationship between plant P uptake and soil measurements. The amounts of variation in plant P uptake accounted for by the regression model was significantly improved by including F in in the model. This indicates the importance of fertiliser dissolution rates in affecting soil P supply, when phosphate fertilisers differing in solubility are applied.

*‘Pasja’ (Brassica campestris x napus) and kale (Brassica oleracea var. acephala L.) were grown at Lincoln, Canterbury, New Zealand in 2008 with different levels of phosphorus (P) fertiliser. Banded or broadcast P fertiliser was applied at 0, 20, 40 and 60 kg P/ha at establishment. Total dry matter (DM) production, the proportion of the leaf and stem and leaf area development were measured over time and related to the biophysical environment. For ‘Pasja’, final DM increased with P rate from 3730 kg DM/ha to ~4900 kg DM/ha at 60 kg P/ha. For kale the increase was from 8710 kg DM/ha for the control to ~11000 kg DM/ha for all P treatments. The leaf to stem ratio declined from 22-31 at 17 days after emergence to 10.4 at the final harvest for ‘Pasja’, which meant the crop was effectively made up mainly of leaf (~90%). The ratio for kale declined from 2.7 at 24 days after emergence to 0.64 at the final harvest. The leaf to stem ratio for both species did not respond to either the method of application or rate of P. Seedling DM accumulation increased with applied P over the first 10 to 17 DAE for ‘Pasja’ and kale respectively. The crops went from shoot growth priority to root growth. The phyllochron of both species was unaffected by P application but responded linearly to the temperature above 0°C. For ‘Pasja’ the phyllochron was 60°Cd compared with 109°Cd for kale. As a consequence ‘Pasja’ developed its canopy and reached critical leaf area index (LAIcrit) earlier than kale. Leaf area index (LAI) for the control crops of both species was lower than for P fertiliser treatments with a maximum of 3.6 for ‘Pasja’ and 3.8 for kale. There was no difference in leaf area indices among the P fertiliser treatments for ‘Pasja’, while kale LAI differed with the rate of P application up to 40 kg P/ha. Total accumulated intercepted solar radiation (RIcum) was 8 and 11% greater for ‘Pasja’ and kale crops respectively when P was applied compared with the control. Thus, the difference in total dry matter yield due to P application was attributed to the difference in RIcum. Neither the method of application or rate of P applied affected the radiation use efficiency (RUE) of either crop. For ‘Pasja’ the RUE was 1.1 g DM/MJ PAR and for kale 1.33 g DM/MJ PAR. Based on this research, it was concluded that P application increased RIcum as a result of increased LAI. The difference in total DM yield was attributed to differences in RIcum. It is recommended that farmers growing ‘Pasja’ and kale under similar conditions to this experiment should apply 40 kg P/ha for ‘Pasja’ and band 20 kg P/ha for kale. *‘Pasja’ is considered both as a species and cultivar in this document as it marketed as such in New Zealand. Technically ‘Pasja’ is a leaf turnip.

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