Resumo-Este trabalho objetivou elaborar um mapa de vulnerabilidade à degradação dos solos da bacia do rio Acaraú, CE, através de Sistema de Informações Geográficas e de metodologia multicritério aditivo. Para a obtenção das classes de vulnerabilidade, foram avaliados os temas geologia, geomorfologia, pedologia, vegetação e clima, definindo-se cinco classes: estável, moderadamente estável, medianamente estável/vulnerável, moderadamente vulnerável e vulnerável. A classe medianamente estável/vulnerável foi a mais representativa, ocupando 9.776 km 2 de extensão (67,8% da bacia), seguida da classe moderadamente estável que ocupou 4.180 km 2 de extensão (mais de 28% da bacia). Os resultados obtidos mostraram a viabilidade da aplicação do método para a elaboração do mapa de vulnerabilidade ambiental que pode ser utilizado na gestão territorial da bacia do Rio Acaraú. Palavras-chave-Risco ambiental. Sistema de Informações Gegoráficas. Gestão agro-ambiental.

The objective of this study was to evaluate the rooting and growth of sweet potato seedlings in trays in response to substrate supplementation with calcium (Ca) and phosphorus (P). Two greenhouse experiments were conducted in a randomized block design with a split plot scheme and eight repetitions. In the Ca experiment, the plots were the doses of 0, 100 and 200 mg kg-1 of Ca, and in the P experiment, by the doses of 0, 150 and 300 mg kg-1 of P. In both experiments, the subplots corresponded to the sampling time of seedlings (15, 30, 45, 60 and 75 days after planting). The Ca present in the substrate was sufficient to promote the proper rooting and growth of sweet potato seedlings in the trays. The Ca supply in excess (200 mg kg-1) adversely affected the growth of seedlings that remained in the tray for more than 60 days. Although the seedlings supplied with P showed higher root growth rate after 45 days, the initial P available in the substrate was sufficient to promote the adequate growth of the seedlings in the trays until 60 days.

Em determinadas condições de relevo, do clima e de uso, com certa frequência pode acontecer acúmulo de sais nos solos, dando lugar à formação dos solos salinos e sódicos - também denominados de solos afetados por sais. A fim de orientar as práticas de manejo e uso das terras da região do Baixo Acaraú, CE, objetivou-se com o presente trabalho gerar um mapa de risco de salinização. Para obtenção das classes de vulnerabilidade, foram avaliados os temas pedologia, geologia, geomorfologia e uso e cobertura das terras e informações de declividade e altimetria, tratados em ambiente SIG com o método multicritério aditivo. Foram definidas quatro classes de risco de salinização: baixo, moderado, alto e altíssimo ou solos naturalmente salinos/sódicos. Foi constatado que 35,47 % da área corresponde à classe de baixo risco de salinização; 26,22 %, à de risco moderado; 8,23 %, à de risco alto; e 19,65 %, à de risco altíssimo.

The storage roots of arracacha have high nutritional value, being rich in carbohydrates, minerals, vitamins A and C, and starch of high digestibility. However, in this crop one of the decisive factors for the production of roots with higher nutritional value is the balanced fertilization. The aim of this study was to evaluate the yield and nutritional quality of storage roots of arracacha, grown at increasing levels of NPK fertilization. The experiment was conducted in the randomized blocks design, with eight replications. The treatments consisted of three NPK levels (AD0 = unfertilized cultivation, AD1 = cultivation with 50% of recommended fertilization, and AD2 = cultivation with 100% ofrecommended fertilization). It was observedthat higher levels of NPK fertilization increase the number, size and marketable yield of storage roots of arracachacrop. NPK fertilization also increases the size and contentsof K, Mg, and Mn of storage roots, without interfering with the pulp pH and contentsof protein, Ca, Cu, and Fe. However, when the increase in root size is not accompanied by an increase in dry matter content, the starch, P, and Zn contents of the roots reduce with increasing levels of NPK fertilization.

Phosphorus (P) is one of the most difficult nutrients for plants to acquire because of its low content in the soil solution. Cassava (Manihot esculenta Crantz) has a thick and sparse absorbent root system; therefore, it is dependent on its association with arbuscular mycorrhizal fungi (AMF) for P acquisition from the soil. Thus, inoculation of cassava with AMF can improve the development of this root crop. This study evaluated the effects of soil disinfection (disinfected vs. natural) and the spore rates of Rhizophagus clarus inoculation (0, 50, 100 and 200 spores per plant) in greenhouse conditions on the initial growth, yield, P acquisition, and P use efficiency of cassava, as well as to evaluate the contribution of the native AMF to P acquisition from the soil. For cassava production in P-deficient soil, inoculation with Rhizophagus clarus significantly increased cassava growth, P uptake, and storage root yield only when the soil was disinfected. When the soil is not disinfected, native AMF contributes up to 86 % of the P taken up by cassava. However, high spore rates of Rhizophagus clarus in natural soil cause detrimental consequences for native AMF by reducing the colonization of the absorbent roots. Therefore, for cassava grown in natural soil under greenhouse conditions, a rate of 50 spores per plant of Rhizophagus clarus is sufficient to promote a 14.5 % increase in the yield of fresh storage roots. A management strategy that favors the native AMF multiplication in the soil is a potential strategy to improve P uptake and yield of cassava in P-deficient soils.