Gestão sustentável do solo em ambientes tropical e mediterrânico

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Ground Management Through Grazing in Rainfed Olive Orchards Provides High Olive Yields and Has Other Potential Benefits for Both the Soil and the Farmer

Publication . Dimande, Paulo; Arrobas, Margarida; Correia, Carlos M.; Rodrigues, M.A.

Soil management in orchards can have several economic and environmental implications. In this study, three different soil management systems were compared in a dry-farmed olive grove: conventional tillage (tillage), glyphosate-based herbicide (herbicide) and sheep grazing. The experiment lasted eleven years (2011-2022) and was carried out after a previous trial conducted on the same plot with the same treatments and duration (2001-2011). However, in the earlier trial, the herbicide and sheep grazing treatments switched positions in the plot, while the tillage treatment remained in its original place. The average total accumulated olive yields between 2011 and 2022 were 225.1, 230.9, and 245.0 kg tree(-1) for the sheep grazing, tillage, and herbicide treatments, respectively. However, no significant differences were observed between the treatments. The levels of total organic carbon in the soil, measured in samples collected in the last year of the study, were 41.3, 33.7, and 37.3 g kg(-1), respectively, for the same treatments. These findings indicated that the tillage treatment exhibited lower soil organic matter content and reduced bioavailability of some nutrients, which raises concerns about its sustainability. On the contrary, employing sheep grazing with an appropriate stocking rate, effectively controlling vegetation in the spring, ensured favourable soil properties and olive yields comparable to the other treatments. Moreover, the sheep grazing approach provides supplementary advantages to the farmer, including revenue from the sale of animal products and the opportunity to transition to organic farming systems, which better align with the preferences of contemporary societies.

2024Journal article

Open access

Intercropped Maize and Cowpea Increased the Land Equivalent Ratio and Enhanced Crop Access to More Nitrogen and Phosphorus Compared to Cultivation as Sole Crops

Publication . Dimande, Paulo; Arrobas, Margarida; Rodrigues, M.A.

Sub-Saharan African smallholder farmers face challenges due to limited access to commercial fertilizers, affecting food security. Exploring the benefits of intercropping is promising, but evaluating crop performance in specific agroecological contexts is crucial. This study in Vilankulo, Mozambique, conducted over two growth seasons (2018 and 2019), aimed to assess the benefits of intercropping maize (Zea mays L.) and cowpea (Vigna unguiculata L., Walp) (M+C) compared to maize (M) and cowpea (C) as sole crops. Key variables for comparison included dry matter yield (DMY), land equivalent ratio (LER), competitive ratio (CR), tissue nutrient concentration, nutrient recovery, and apparent N fixation (ANF). This study also examined the effects on cabbage (Brassica oleracea L.), cultivated as a succeeding crop, and soil properties. In 2018, maize plants were severely affected by drought and did not produce grain. This year, cowpea grain yields were 2.26 and 1.35 t ha-1 when grown as sole crop or intercropped. In 2019, maize grain yield was 6.75 t ha-1 when intercropped, compared to 5.52 t ha-1 as a sole crop. Cowpea grain yield was lower when intercropped (1.51 vs. 2.25 t ha-1). LER values exceeded 1 (1.91 and 1.53 for grain and straw in 2019), indicating improved performance in intercropping compared to sole crops. In 2019, CR was 1.96 for maize grain and 0.58 for cowpea grain, highlighting the higher competitiveness of maize over cowpea. Cowpea exhibited higher average leaf nitrogen (N) concentration (25.4 and 37.6 g kg-1 in 2018 and 2019, respectively) than maize (13.0 and 23.7 g kg-1), attributed to its leguminous nature with access to atmospheric N, benefiting the growth of maize in intercropping and cabbage cultivated as a succeeding crop. Cowpea also appears to have contributed to enhanced phosphorus (P) absorption, possibly due to access to sparingly soluble P forms. In 2019, ANF in M+C was 102.5 kg ha-1, over 4-fold higher than in C (25.0 g kg-1), suggesting maize accessed more N than could cowpea provide, possibly through association with endophytic diazotrophs commonly found in tropical grasses.

2024Journal article

Open access

Em climas tropicais quentes e solos arenosos, um guano de morcego mineralizou-se muito rapidamente comportando-se como um fertilizante mineral

Publication . Dimande, Paulo; Arrobas, Margarida; Rodrigues, M.A.

Na África Subsaariana, a gestão da fertilidade do solo deve depender de corretivos orgânicos locais uma vez que a maioria dos agricultores não tem acesso a fertilizantes industriais. Em Vilankulo, Moçambique, em algumas grutas existem depósitos naturais de guano de morcego e os agricultores aprenderam as preparar biochar por um processo artesanal. Sendo estes recursos orgânicos escassos, ainda que prometedores no seu valor fertilizante, torna-se muito importante aprender a geri-los corretamente para maximizar a produtividade das culturas. Neste estudo, com a cultura do milho (cv. MRI 514), foram estabelecidos nove tratamentos consistindo na aplicação de 5 (G5) e 10 (G10) t ha-1 de guano à sementeira, 5 (B5) e 10 (B10) t ha-1 de biochar à sementeira, 5 [G5(-1)] e 10 [G10(-1)] t ha-1 de guano um mês antes da sementeira, 1 e 4 (B1G4) e 2 e 8 (B2G8) t ha- 1 de biochar e guano, respetivamente, na sementeira e uma testemunha não fertilizada (T). Os tratamentos G10 e B2G8 originaram as maiores produtividades de milho (3,77 e 2,68 t ha-1 em 2018 e 5,05 e 5,17 t ha-1 em 2019, respetivamente), sendo os resultados estatisticamente superiores à testemunha (1,35 e 1,63 kg ha-1, respetivamente). O azoto aparentemente recuperado do guano de morcego foi próximo de 100%, mostrando uma mineralização quase completa durante a estação de crescimento do milho, devido à baixa relação carbono/azoto do corretivo orgânico e a condições ambientais muito favoráveis à mineralização. Devido à rápida mineralização, não é recomendável antecipar a aplicação do corretivo orgânico relativamente à sementeira, pois reduz a eficiência do uso dos nutrientes. Biochar não influenciou significativamente as propriedades do solo nem contribuiu significativamente para a nutrição das plantas, sendo o seu uso recomendado em combinação com outros materiais de maior valor fertilizante.

2023Conference object

Open access

Sewage sludge showed high agronomic value, releasing nitrogen faster than farmyard manure

Publication . Dimande, Paulo; Arrobas, Margarida; Correia, Carlos M.; Rodrigues, Manuel Ângelo

The use of fertilizers in agriculture, particularly organic fertilizers such as sewage sludge, is a key research priority due to its impacts on crop productivity, production costs, environmental risks and the push for a more circular economy. This study, conducted in Bragan & ccedil;a, northeastern Portugal, focused on forage maize during the 2022 and 2023 growing seasons. Eight fertilization treatments were established corresponding to the application of mineral nitrogen (N) at rates of 50 (N50), 100 (N100), 150 (N150) and 200 (N200) kg ha(-1), three organic amendments applied at a rate equivalent to 200 kg ha(-1) of N, namely sewage sludge (SS200), cow manure (CM200) and sheep manure (SM200), and a non-fertilized control (N0), with the aim of assessing the agronomic value of these treatments for forage maize (Zea mays L.). Maize dry matter yield (DMY) ranged from 10.8 to 20.3 t ha(-1) in 2022 and 13.7 to 23.6 t ha(-1) in 2023 for N0 and N200, respectively. Organic amendments produced 14.7-17.7 t ha(-1) in 2022 and 20.5-24.4 t ha(-1 )in 2023. Increased mineral N rates resulted in higher soil inorganic N content, N concentration in leaves and N recovery in tissues, with organic amendments showing lower values than crops fertilized with N200. However, due to cumulative nutrient release, organic amendments improved DMY and N use efficiency in the second year. Sewage sludge mineralized rapidly due to its low carbon (C)/N ratio and absence of hard-to-degrade compounds. It is also rich in phosphorus (P), enhancing its fertilizing value. Although nitrate leaching and denitrification potential appeared lower with organic amendments, long-term applications may increase risks, requiring careful monitoring to ensure sustainable and safe practices.

2025Journal article

Open access