This study aims to explain the effects of silicon on chlorophyll and to measure gas exchange and carbohydrate levels in two Lycopersicon esculentum cultivars that are exposed to drought. The experimental design used in this study was a randomised combination of five different water and silicon conditions (control, water deficit + 0.00 μmol Si, water deficit + 0.25 μmol Si, water deficit + 1.00 μmol Si, and water deficit + 1.75 μmol Si) applied to the two cultivars (Super Marmante and Santa Cruz). Parameters measured were gas exchanges, chlorophylls, and total soluble carbohydrates. Silicon at concentrations of 0.25, 1.00, and 1.75 μmol induced a gradual increase in the total chlorophyll levels. A correlation analysis revealed a linear, positive interaction between the leaf water potential and the total chlorophyll (r = 0.71; P < 0.05). This study confirmed the hypothesis that silicon has a beneficial effect with regard to chlorophyll. Under water-deficient conditions, both cultivars showed an increase in chlorophyll a when treated with silicon in addition to changes in the total chlorophyll levels. These results were supported by the change in leaf water potential. In addition, a reduction of the effects of water restriction was also observed in the transpiration rate, the stomatal conductance and in the levels of total carbohydrates.
PK rock biofertilizers made from rocks and elemental sulphur inoculated with Acidithiobacillus improve yield of many short cycle plants similarly to soluble fertilizers. This study aims to evaluate the potential of PK rock biofertilizers for grape cultivation in the Brazilian San Francisco Valley. Three sources of P and K were compared: (a) soluble fertilizers, (b) biofertilizers plus elemental sulphur inoculated with Acidithiobacillus, and (c) ground phosphate and potash rocks, all at three application rates. A control treatment without P and K fertilization was added. Earthworm compound was applied as N source in all treatments. Grape (Vitis vinifera cv. Italia Pirovano) was cultivated in a dystrophic Planossol (medium texture) at the San Francisco River in the Brazilian Semiarid. P, K, Ca, Mg, S-SO 4 2-and Fe concentrations were analyzed in grape leaves and fruits. The results showed adequate leaf contents of S-SO 4 2-, K, and Fe with PK biofertilizer application plus earthworm compound, which indicates this may be alternative to soluble fertilizer for grape in soils with low available P and K.
Land use and management systems are factors that control availability and nitrogen (N) forms in soil environment. The aim was to evaluate the inorganic N fractions dynamics in soil under different use and management systems in Brazilian Eastern Amazon conditions. Soils were sampled at depths of 0.0-0.1 and 0.1-0.2 m in areas under pasture (PAST), no-tillage (NT), conventional tillage (CT) and a reference area under fallow vegetation (FV). In the samples, soil organic matter (SOM), total-N, ammonium (N-NH4+) and nitrate (N-NO3-) contents were determined and the urease enzyme activity was measured. In CT and NT the SOM contents were similar to those found in FV, with an average of 36.7 g kg-1, while under PAST there was a 16.6% reduction when compared to the reference area. The total-N levels followed the same dynamics found for SOM. The ammonium concentration was 2.4 times higher in soils under FV (14 mg kg-1) when compared to other systems and nitrate followed the order NT> CT> FV=PAST. The pasture (44 µg N-NH4+ g-1 soil h-1), among soils for agricultural use, induced the highest ureolytic activity. The preserved soil conversion from native forest to pasture caused a 16.6% reduction in the SOM contents and 55.5% and 46% for ammonium and nitrate, respectively. On the other hand, the NT system has the capacity to accumulate SOM in a similar way to the area of native vegetation studied, as well as a high capacity to retain N in the soil, preferentially in the nitrate form.
Avaliar o potencial de diferentes cultivares de soja em condições complexas como da região amazônica é necessário para investigar a capacidade de adaptação e o comportamento em vários aspectos dessas cultivares. Neste sentido, objetivou-se avaliar o comportamento fenológico, nutricional e de produtividade de cultivares de soja em condições edafoclimáticas do sudeste Paraense. Para isso, foram testadas nove cultivares: BRS 279RR, BRS 333RR, BRS 325RR, BRS 9090RR, BRS 8990RR, BRS SambaíbaRR, P98R31, P98Y51 e P98Y70. O delineamento experimental foi em blocos casualizados, com densidade de 240.000 plantas.ha-1, com quatro repetições. Foram avaliadas altura de planta e de inserção da primeira vagem (cm), florescimento e maturação (dias) e produtividade de grãos (kg.ha-1). Além disso, foi quantificado o teor de N, P e K nas folhas. Para altura de plantas, destacaram-se as cultivares BRS 9090 RR, BRS 333 RR e P98Y70, com alturas de 73,25; 72,25 e 71 cm, respectivamente. A inserção da primeira vagem variou de 8,75 (P98Y51) a 16,75 cm (BRS 333 RR). A floração foi atingida entre 34 (P98R31) e 42 (BRS 333RR e P98Y70) dias após a emergência. O período de maturação teve início mínimo aos 98 dias (P98R31) e máximo aos 119 dias (BRS 333 RR) após a emergência. As maiores produtividades foram registradas para as BRS’s e P98Y70, variando entre 1890 e 3192 kg.ha-1. O teor foliar de N, P, K não diferiu entre as cultivares testadas. A BRS 333 RR, mostrou excelente desempenho das características agronômicas.
The nitrogen (N) fertilization synthetic or biological is primordial for food production worldwide. The consumption of N fertilizers in agricultural systems increased in exponential scale, mainly in developing countries. However, some negative points are associated to industrial N consumption; consequently the industry promoted ways to minimize N losses in production systems of tropical agriculture. Biological nitrogen fixation is a very important natural and sustainable process for the growth of leguminous plants, in which many micronutrients are involved, mainly as enzyme activators or prosthetic group. However, other mechanisms in the rhizosphere and molecular region still need to be clarified. Therefore, the aim of this chapter is to compile information about the historical and current affairs about the advances in N fertilization in tropical environments through a history from N fertilization worldwide, N balance in the main agricultural systems, introduction of alternative ways to avoid N losses, advances between BNF and micronutrients, as well as the effects of N absence in plant metabolisms. Biological nitrogen fixation is a very important natural process for the growth of leguminous plants, in addition many metallic nutrients, micronutrients, are involved in BNF metabolism, mainly as enzyme activators or prosthetic group. But other mechanisms in the rhizosphere and molecular region still need to be clarified.
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