Effects of soils flooding. II. Influence on nutrient uptake and growth of rice (Oriza sativa)

Com a finalidade de estudar o efeito da inundação do solo sobre a absorção e o crescimento do arroz, foi instalado um experimento em casa de vegetação. O experimento estava constituído de 16 tratamentos (quatro solos e quatro níveis de fósforo, correspondentes a 0, 40, 80 e 120 kg de P2O3/ha), em três repetições. Imediatamente depois da semeadura, os vasos foram inundados com uma lâmina de água de 3 cm sobre a superfície do solo, tendo-se permitido o desenvolvimento de quatro plantas de arroz (Oriza sativa L. var. Sinaloa A 68) por unidade experimental. Ao final do experimento, colheram-se as partes aéreas das plantas, considerando-se o seu peso seco como índice do crescimento. A produção de matéria seca foi muito pequena em todos os solos e níveis de fósforo empregados. A análise química quantitativa do fósforo, nitrogênio, potássio, cálcio, magnésio, ferro e manganês das tolhas e caules do arroz permitiu verificar que o pequeno crescimento das plantas foi causado por múltiplas deficiências nutricionais. Entre estas, estavam envolvidas, principalmente, a do fósforo, do potássio, do cálcio e do magnésio. Foi verificado que as deficiências detectadas não foram devidas à escassez dos nutrientes nos solos e, sim, às alterações nos processos de absorção. Estas alterações foram atribuídas à redução do solo, assim como à presença de ácidos orgânicos e outros produtos resultantes da decomposição anaeróbia da matéria orgânica, na zona radicular.The objective of this work was to study the influence of waterlogging on nutrient uptake and growth of rice. The experiment was composed of 16 treatments (4 soils and 4 levels of phosphorus, corresponding to 0, 40, 80 and 120 kg/ha), with 3 replications. Immediately after sowing, the soils were flooded. Four rice plants (Oriza sativa L. var. Sinaloa A 68) were grown in each pot. After 84 days the above ground portions of the plants were harvested. The dry matter weight was used as the yield index. Growth was extremely limited in all treatments. The quantitative chemical analysis of P, N, K, Ca, Mg, Fe and Mn in the stems and leaves indicated that the poor growth was caused by multiple nutritional deficiencies. Among these, deficiencies of phosphorus, potassium, calcium and magnesium were involved. The detected deficiencies were not caused by lack of nutrients in the soils but by alterations in the absorption process. These alterations were caused by soil reduction, and the accompanying presence of organic acids and other products of anaerobic decomposition in the root zone.

Efeitos da inundação do solo. I. influencia sobre o pH, o potencial de óxido-redução e a disponibilidade do fósforo no solo

Four soils and four levels of phosphorus (0, 40, 80 and 120 kg/ha) have been used with the objective of studying the influence of waterlogging on pH, redox potential and phosphorus availability. The pH, the Eh, the phosphorus of the soil solution and phosphorus extracted from soil by an anion exchange resin were determined every 7th day during the flooding period. The pH of the acid soils increased and the pH of the alkaline soil decreased after inundation. In both cases the final values were between 6.5 and 7.0. The redox potentials of the soils changed remarkably after waterlogging. The Eh of the soils decreased rapidly for the 5 first weeks of submergence followed by a slow decrease between the 5th and 7th weeks, at which time Eh values became stable, between - 200 and - 300 mV. Phosphorus applied to soil as a fertilizer was fixed at the beginning of the flooding. Availability increased only after pH and Eh changes had taken place. Both extracted and soil solution phosphorus increased with time of inundation. Correlation coeficients between these two forms of phosphorus were 0.91, 0.85, 0.90 and 0.88 respectively for the soils La Granja loam, Mesillas clay, Hogamacho clay and Piedras Negras clay. It was observed that soil temperature influenced the velocity of changes on pH, Eh and phosphorus availability.Quatro solos e quatro níveis de fósforo (0, 40, 80 e 120 kg de P 2O5/ha) foram usados com a finalidade de estudar a influência da inundação dos solos sobre o pH, o potencial de óxido-redução e a disponibilidade do fósforo dos solos. Para tal, a cada sete dias e durante todo o período de inundação, se determinaram o pH, o Eh, o fósforo presente na solução do solo e o fósforo extraído pela resina de intercâmbio aniônico, Amberlita IRA-400. O pH dos solos ácidos aumentou e o do solo alcalino diminuiu com o tempo de inundação. Em ambos os casos, os valores finais se estabilizaram entre 6,5 e 7,0. A alteração dos valores do potencial de óxido-redução dos solos foi muito pronunciada. Houve uma rápida diminuição do Eh nas primeiras semanas de submergência, seguida por uma diminuição mais lenta entre a quinta e sétima semanas. A partir desse período, os valores se mantiveram estáveis entre —200 e —300 milivolts. O fósforo, aplicado ao solo como fertilizante, foi fixado no início da inundação. Somente depois que ocorreram alterações no pH e no Eh dos solos é que aumentou a disponibilidade do fósforo. Tanto o fósforo extraído como o presente na solução do solo aumentou consideravelmente com o transcurso do tempo. Os coeficientes de correlação entre estas duas formas de fósforo foram de 0,91, 0,85, 0,90 e 0,88, respectivamente para os solos franco La Granja, argila Mesillas, argila Hogamacho e argila Piedras Negras. Foi verificado que a temperatura do solo influencia a velocidade de modificação do pH e do Eh, assim como a velocidade de liberação do fósforo do solo.

Management of cerrado soils. I. Production of bean, wheat and rice in a dark-red latosol.

Um experimento foi instalado em Latossolo Vermelho-Escuro distrófico (LEd) de Goianira, GO, para estudar a influência da calagem, correção com fosfato, adubação verde, e micronutrientes na produção de arroz, feijão e trigo, em um sistema de agricultura intensiva com três cultivos anuais. Nos três primeiros cultivos constatou-se o efeito do adubo verde na produção de arroz; e o efeito da calagem na produção de trigo e de feijão. A produção de feijão também foi influenciada pela adubação verde. A mistura de micronutrientes + S somente teve efeito significativo no primeiro cultivo do feijoeiro. Os três cultivos de trigo também foram influenciados pelos micronutrientes + S, mas a diferença média em produtividade foi menor que 10%. Após o quarto cultivo, as produtividades em todos os tratamentos não diferiram estatisticamente e mostram a importância da incorporação dos resíduos orgânicos e adubação de manutenção na produtividade de feijão, trigo e arrozAn experiment has been carried out in a distrophic dark-red latosol (oxisol) of Goianira, GO, Brazil, to study the effect of lime, corrective phosphate fertilization, green manure and micronutrients on the yield of bean, wheat and rice in an intensive agriculture system with three crops per year. In the first three crops the effect of green manure on the yield of rice and the effect of lime on the yield of bean and wheat were determined. The bean yield was also influenced by the green manure. The mixture of micronutrients + S increased the yield of bean in the first crop. All three crops of wheat were influenced by micronutrients + S but the increase in yield was less than 10%. In the fourth and following crops the yield of all treatments was not statistically different. This shows the importance of plant residues incorporation and maintenance fertilization on the growth and yield of bean, wheat and rice

Porous ceramic cups for soil solution extiaction

Em um solo bem drenado (LE) e em um solo de várzea (GPI-1) submetido a inundação, analisaram-se semanalmente soluções coletadas em campo, através de cápsulas porosas mantidas no solo durante todo o período de amostragem (15 semanas para o LE e 22 semanas para o GPII). Foram observados o movimento de Ca, Mg, K e NO no perfil do solo LE e o aumento na concentração de Fe no solo GPII. A progressiva obstrução dos poros das cápsulas com partículas coloidais em ambos os solos e a deposição de óxidos-hidróxidos de Fe na superfície interna das cápsulas no solo inundado foram alguns dos inconvenientes observados no método.Sou selution samples of a well drained latosol (LE-oxisol) and of a lowland flooded soU (Low-}lumic Gley - LHG) were collected with porous ceramic cups and analysed weekly. The pomos ceramic cups were kept iii the soU during the whole sampimg periods (15 weeks for the Lii soil and 22 weeks for the LIIG soil). The movement of Ca, Mg, K and NOT ipi the LE soU profile and the iiicrease in Fe in the solution of the LUO soU were observed. Obstruction of the ceramie cups pores by a progressive deposition of coiloidal material on the external surface of tbe cups and precipitation of Fe oxi-hydroxides on the internal surface of the cups were problems one observed that reduced the efficiency of the ceramic eups in laking reliable soi.l solution sample

Calagem, adubação com micronutrientes e produção de arroz irrigado e feijoeiro em solo de várzea

Grain production, and absorption of nutrients by flooded rice (cv. Cica-8, and BR IRGA-409) and dry-bean (cv. Carioca, and LM 30030) planted in successive and alternate crops in a Low Humic Gley soil of the county of Goianira, GO, Brazil, were evaluated as affected by treatments which associated five lime doses and two micronutrients doses. Lime did not influence the grain yield of rice or bean, and micronutrients increased significantly (p < 0.05) the yield of beans, but not of rice. In the plots which had received no micronutrients, the bean plants showed symptoms of B deficiency and Mn toxicity. In all treatments, the rice cv. BR IRGA-409 absorbed more Fe than cv. Cica-8, but none of the two cultivars showed any symptom of Fe toxicity.Avaliou-se o efeito de tratamentos que associaram cinco doses de calcário e duas doses de micronutrientes aplicados a um solo Gley Pouco Húmico do município de Goianira, GO, sobre a produção de grãos e a absorção de nutrientes pelas plantas de arroz irrigado (cultivares Cica-8 e BR IRGA-409) e de feijoeiro (cultivar Carioca e linhagem LM 30030), em cultivos sucessivos e alternados. A calagem não influenciou a produção de grãos das duas culturas, e os micronutrientes causaram aumento significativo (p<0,05) apenas da produção de grãos do feijoeiro. Nas parcelas sem micronutrientes, as plantas de feijoeiro mostraram sintomas semelhantes aos de deficiência de B e toxidez de Mn. Em todos os tratamentos, a cultivar de arroz BR IRGA-409 acumulou mais Fe na parte aérea do que a cultivar Cica-8, mas nenhuma das cultivares mostrou sintomas de toxidez do elemento

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost