Nitrogen and phosphorus fertilization of sunflower crop in alkaline Cambisol

ABSTRACT Sunflower is a crop that has aroused the interest of farmers because of its adaptability to wide climatic conditions and for its use in biodiesel production. However, there are only a few studies on sunflower fertilization in alkaline soils. This study aimed to evaluate nitrogen (N) and phosphorus (P) fertilization in sunflower (Helianthus annuus L.) cultivated in alkaline soil. A field experiment was carried out in Baraúnas-RN, Brazil, in a Haplic Cambisol derived from calcareous rock, where the sunflower H-251 hybrid was cultivated. The treatments were a combination of four doses of N (30, 60, 90 and 120 kg ha-1) and four doses of P2O5 (30, 60, 90 and 120 kg ha-1). Sunflower growth and yield increased with the doses of N and P2O5. Doses of 30 kg ha-1 of N and 30 kg ha-1 of P2O5 were more economical, corresponding to grain yield of 2378 kg ha-1. Critical levels associated with these doses of N and P2O5 were 28.2 g kg-1 for N leaf content, 2.84 for P leaf content, and 6.75 mg dm-3 for soil available P extracted by Mehlich-1

Contribution of non-exchangeable potassium forms and its accumulation in corn plants

ABSTRACT The state of Paraíba, Brazil, has soils from well- to poorly-developed, in which potassium (K) is found in different levels, forms and, consequently, with varying availability to plants. The objective of this study was to evaluate the contribution of non-exchangeable K forms to corn plants in 12 soils from Paraíba state, along four successive cycles. The experimental design was completely randomized block with three replicates and the 24 treatments consisted of the combination between two K levels (0 and 100 mg dm-3) ​​and 12 soils. Before and after each cycle, subsamples of 0.2 dm3 were collected in each pot for the determination of non-exchangeable K (Kne), exchangeable K (Ke) and soluble K (Ks). For each cycle, dry matter production, dry matter K content and plant K content (absorbed K) were determined. In the studied soils, the amounts of absorbed K after successive cycles were higher than the amounts of exchangeable K released, which shows the contribution of non-exchangeable K forms to corn nutrition

Phosphorus availability as a function of its time of contact with different soils

ABSTRACT Phosphorus (P) availability is related to soil sorption capacity and is relevant to planning P fertilization and evaluating its residual effect. The aim of this work was to evaluate the P availability to maize plants after different incubation times of six soils from Paraíba state. For this, four doses of P (0, 100, 200 and 300 mg dm-3) were applied in samples of six soils for 0, 30, 60, 90, 180, 240 and 360 days. After the incubation time, the soil samples received fertilization with macro and micronutrients and were cultivated with maize for 35 days, when they were harvested and analyzed to verify dry matter and P content in soil. The increase in the time of contact of P with the soil decreased P availability to plants; however, the formation of non-labile P was negligible in most soils. After 360 days of incubation, between 26 and 71% of P applied at the highest dose was recovered

Nitrogen and phosphorus fertilization of sunflower crop in alkaline Cambisol

<div><p>ABSTRACT Sunflower is a crop that has aroused the interest of farmers because of its adaptability to wide climatic conditions and for its use in biodiesel production. However, there are only a few studies on sunflower fertilization in alkaline soils. This study aimed to evaluate nitrogen (N) and phosphorus (P) fertilization in sunflower (Helianthus annuus L.) cultivated in alkaline soil. A field experiment was carried out in Baraúnas-RN, Brazil, in a Haplic Cambisol derived from calcareous rock, where the sunflower H-251 hybrid was cultivated. The treatments were a combination of four doses of N (30, 60, 90 and 120 kg ha-1) and four doses of P2O5 (30, 60, 90 and 120 kg ha-1). Sunflower growth and yield increased with the doses of N and P2O5. Doses of 30 kg ha-1 of N and 30 kg ha-1 of P2O5 were more economical, corresponding to grain yield of 2378 kg ha-1. Critical levels associated with these doses of N and P2O5 were 28.2 g kg-1 for N leaf content, 2.84 for P leaf content, and 6.75 mg dm-3 for soil available P extracted by Mehlich-1.</p></div

Production and quality of okra produced with mineral and organic fertilization

ABSTRACT Okra, Abelmoschus esculentus (L.) Moench, is a vegetable with annual fruit native to hot regions of Africa, well adapted to the conditions of the Northeast and Southeast regions of Brazil, where it is widely used by small farmers. This study aimed to evaluate the effect of mineral and organic fertilization on the production and quality of okra fruits. The experiment was conducted in randomized block design, with three replicates and eleven treatments defined according to a Baconian matrix. Treatments consisted of doses of N (0, 100, 200 and 300 kg ha-1), P (0, 100, 200 and 300 kg ha-1) and K (0, 80, 160 and 240 kg ha-1), as well as absence and presence of organic compost (30 t ha-1). The following parameters were evaluated: plant height, stem diameter, number of leaves, production of fruits plant-1, number of fruits plant-1, fruit length and diameter and fruit quality (pH, soluble solids, titratable acidity, vitamin C and electrical conductivity). The crop is demanding in terms of K and N fertilizations, with increments of 15.8 and 36% in the mean number and diameter of fruits, respectively. Organic fertilization did not influence the vegetative growth of okra, but was beneficial to the production of fruits with higher vitamin C content, 52% higher than the contents found in fruits produced without such input