Organic fertilizers are a viable alternative to increase oilseed productivity in family agriculture systems. The study aimed to evaluate the effects of timing and placement of cattle manure and/or gliricidia (Gliricidia sepium Jacq. Walp) prunings on cotton (Gossipium hirsutum L.) and sunflower (Helianthus annuus L.) nutrient accumulation and biomass productivity. Experiments were carried out in 2010 and 2011 in Taperoá, Paraíba, Brazil. The organic fertilization treatments were: GI - gliricidia incorporated before planting; GS - gliricidia applied on surface 45 days after planting (DAP); MI + GI - manure and gliricidia incorporated before planting; MI + GS - manure incorporated before planting and gliricídia applied on the surface 45 DAP; MI - manure incorporated before planting; and T - with no organic fertilization. In 2010, treatment MI + GS increased N, P, and K accumulation in cotton (12 and 7 kg ha^-1) as well as in sunflower (20 and 29 kg ha^-1). In 2011, GI and GS treatments resulted in higher N, P, K accumulations in both crops. The highest cotton productivity in 2010 was obtained with MI + GS treatment (198 kg ha^-1) and in 2011 with GS treatment (594 kg ha^-1). For sunflower, MI + GS treatment yielded the highest productivity in 2010 (466 kg ha^-1) and GI treatment in 2011 (3542 kg ha^-1). GI and MI + GS treatments increased total biomass productivity for cotton and sunflower. The treatment that combined both cattle manure incorporated into the soil before planting and gliricidia applied on the surface 45 days after planting was the most viable management strategy.

O aproveitamento de resíduos agroindustriais na forma de composto orgânico, pode resultar em maior sustentabilidade para sistemas agrícolas. Propôs-se, neste trabalho, analisar a qualidade final do composto orgânico em relação à composição em nutrientes e à presença de substâncias toxocologicamente ativas. Avaliaram-se as combinações de talo de fumo triturado, esterco e rúmen bovino (TF+EB+RB), talos de fumo, esterco bovino e Microsept-Pó (TF+EB+MP) e talos de fumo mais esterco bovino (TF+EB). Amostras médias de cada composto foram analisadas para determinação da concentração em macro e micronutrientes, aos 60 e 120 dias e, para verificar a concentração de nicotina e a presença ou não de resíduos agrotóxicos na matéria-prima (TF) nos compostos obtidos aos 120 dias. Os dados obtidos demonstraram alta concentração de potássio (K), nitrogênio (N), cloreto (Cl) e ferro (Fe) no composto final em relação aos demais macro e micronutrientes. Não se detectaram resíduos de agrotóxicos na matéria-prima (TF) nem a presença de nicotina nas amostras obtidas aos 120 dias, demonstrando ausência de risco de impacto ambiental no uso agrícola desses compostos. No final do processo de compostagem a mistura TF+EB foi a que resultou no composto orgânico com maior concentração em macro e micronutrientes.

The stable fraction of soil organic matter (SOM) has received considerable attention due to concerns about the sustainability of agricultural systems. The main structural characteristics of the SOM of an Entisol in the semi-arid region of Paraíba state, Brazil, after 6 years of cultivation of annual crops with different organic fertiliser treatments, were determined. Six different treatments were evaluated, as follows: (1) gliricidia prunings (Gliricidia sepium Jacq. Walp) incorporated into the soil before planting (GI); (2) cattle manure incorporated before planting (MI); (3) gliricidia applied after planting (GS); (4) manure and gliricidia incorporated before planting (MI + GI); (5) manure incorporated before planting and gliricidia applied after planting (MI + GS); and (6) a control treatment. Spectroscopic techniques were used to analyse carbon in whole soil samples (0–20 cm), as well as in fulvic acid (FA) and humic acid (HA) extracts. Surface-applied gliricidia resulted in the highest SOM content. Laser-induced fluorescence spectroscopy showed that MI + GS contributed to increases in the degree of humification, whereas for the HA fraction, the highest degree of humification occurred with the GS treatment. The ultraviolet–visible absorbance spectra of FA fractions indicated the presence of fresh soluble SOM in all treatments except GS, and mid-infrared region spectra revealed no differences in the chemical structure of the HA fractions. Application of gliricidia prunings (GI and GS), which are nitrogen rich and highly labile, resulted in low HA transformations compared with the control based on nuclear magnetic resonance analysis. Therefore, gliricidia, whether incorporated before planting or applied after planting, decreases the labile fractions of SOM, probably because of its higher decomposition rates.

Effects of annual organic fertilization on maize and sunflower yields and on physical and chemical characteristics of a Fluvisol were evaluated in the semiarid area of Paraiba state, from 2007 to 2011. The experiment was a block design in a 4 × 2 factorial arrangement, corresponding to one control and three fertilizer treatments (cattle manure and Gliricidia sepium and Croton sonderianus prunings) and two application procedures (soil surface or incorporated in the 0–10 cm layer), with four replications. Maize was grown in the first 3 years and then sunflower was grown for 2 years. Grain and straw yields increased with fertilization, especially in the years of good rains (maize, 0–61%, reaching 3.4 Mg ha⁻¹ of grain; sunflower, 48–112%, reaching 1.4 Mg ha⁻¹ of achenes), differing only slightly between fertilizer types and form of application. All fertilizers incorporated for 5 years reduced water infiltration time (20–50%), but only manure and G. sepium reduced soil bulk density (about 10%) and increased soil porosity (7–10%). Manure increased soil pH (0.7–1.0 units). Surface application of manure and C. sonderianus increased soil organic matter (28 and 72%) and phosphorus concentrations (about 70%). We suggest that, in sites with soil physical problems (slow water infiltration, high soil compaction, and low porosity), organic fertilizers may lead to better responses if incorporated into the soil. If there is a need for greater improvement of soil organic matter, nutrients and water conservation, surface applied organic manure and C. sonderianus may be a better management practice.