Phosphorus and silicon effects on growth,yield, and phosphorus forms in potato plants

Silicon (Si) can increase phosphorus (P) use efficiency (PUE) by increasing P availability in the soil and altering P metabolism in the plant, thus resulting in improved yield under low soil P conditions. The objective was to evaluate the effect of P (10, 50, 100, and 200?mg dm^?3) and Si (0, 50, and 200?mg dm^?3) interrelationship on P and Si uptake by plants, forms of P in leaves and tubers, plant growth, and tuber yield of potato plants. Silicon supply increased organic and inorganic P in the leaves. At low soil P rates, Si also increased organic P in the tubers. However, alterations in the P metabolism of potato plants with Si supply did not promote significant changes in dry matter (DM) production and tuber yield. Phosphate fertilization increased growth and yield of plants. Silicon uptake by the plants were also increased by phosphate fertilization with soil Si supply.     

Reactivity of Sedimentary and Metamorphic Limestones of Different Particle Sizes under Controlled Conditions

The efficiency of limestone in amending soil acidity is primarily based on the particle size and the neutralization value of the ground rock, but the origin of the rock can also affect its reactivity. The aim of this work was to evaluate, under controlled conditions, the efficiency of the reactivity of sedimentary limestones of different particle sizes in neutralizing soil acidity. The experiment was conducted using a clayey and a sandy soil, and the treatments consisted of four samples of a sedimentary limestone (with the same neutralization values but different particle sizes), two metamorphic limestones and an untreated control. In the first months of incubation, the sedimentary limestones demonstrated higher soil amelioration abilities than the metamorphic limestones, but all samples used in the study achieved the goal of neutralizing soil acidity to desired values: a base saturation (BS) of ~70% and a pH > 6.0. In sedimentary limestones, the availability of calcium (Ca) and magnesium (Mg) was more closely related to the levels of Ca oxide (CaO) in the amendment than to the size of the particles. The results of this study suggest that the currently used equation may underestimate the reactivity of certain limestones.     

Spatial variability of leaf macronutrient concentration and fruit production of an Arabica coffee plantation using two sampling densities

Precision Agriculture - The nutritional and productive attributes of Arabica coffee (Coffea arabica L.) can vary spatially within cultivated areas. Precision farming techniques applied to coffee...