A B S T R A C TThis study aimed to evaluate the production and mineral nutrition of Piatã grass as a function of nitrogen and potassium fertilization in Oxisol collected in the Cerrado. The experiment was carried out in a greenhouse, the experimental design was completely randomized, in a 5 x 5 factorial scheme, corresponding to five nitrogen doses (0, 100, 200, 300 and 400 mg dm -3 of N) and five potassium doses (0, 90, 180, 270 and 360 mg dm -3 of K 2 O), with four replicates. Three cuts of the shoots were performed every 30 days. Chlorophyll index, dry mass of shoots and roots, and nitrogen and potassium contents in the leaves were evaluated. The dry mass of shoots showed interaction between nitrogen and potassium in the three cuts; in the second and third cuts, it had maximum production at the nitrogen and potassium doses of 254 and 158 mg dm -3 , in the second, and 250 and 306 mg dm -3 in the third, respectively. The nitrogen and potassium contents are influenced as a function of nitrogen and potassium fertilization isolated by factor. The nitrogen and potassium ratio in the Piatã grass crop was around 1:1.Nitrogênio e potássio no cultivo do capim-piatã em solo do Cerrado brasileiro R E S U M O Objetivou-se avaliar a produção e a nutrição mineral do capim piatã em função da adubação nitrogenada e potássica em Latossolo Vermelho coletado no Cerrado. Realizouse o experimento em casa de vegetação, o delineamento experimental foi inteiramente casualizado em esquema fatorial de 5 x 5 sendo cinco doses de nitrogênio (0, 100, 200, 300 e 400 mg dm -3 ) e cinco doses de potássio (0, 90, 180, 270 e 360 mg dm -3 ), com quatro repetições. Realizaram-se três cortes da parte aérea a cada 30 dias. Foram avaliados o índice de clorofila, a massa seca da parte aérea e das raízes, a concentração de nitrogênio e de potássio, nas folhas. A massa seca da parte aérea apresentou interação entre o nitrogênio e o potássio nos três cortes sendo que no segundo e no terceiro apresentou máxima produção nas doses de nitrogênio e potássio, de 254 e 158 mg dm -3 no segundo e de 250 e 306 mg dm -3 no terceiro, respectivamente. As doses de nitrogênio e de potássio apresentaram interação significativa para a massa seca da parte aérea do capim piatã, nos três cortes. As concentrações de nitrogênio e potássio são influenciadas em função da adubação nitrogenada e potássica isolada por fator. A relação de nitrogênio e potássio no capim piatã é de 1:1. Key words:Brachiaria brizantha nitrogen content potassium content N:K ratio in plants Palavras-chave: Brachiaria brizantha concentração de nitrogênio concentração de potássio relação N:K nas plantas
The quality of cherry tomato fruits is directly related to the management strategies used in the production system, such as irrigation and fertilization. This study aimed to assess the quality of cherry tomato fruits cultivated under water availability and potassium fertilization. The experiment was carried out in a greenhouse in pots of 12 dm 3 of an Oxisol. The experimental design was a randomized block design in a 5 2 fractional factorial arrangement with five water availabilities in the soil (4, 14, 24, 34, and 44-kPa), five potassium doses (0, 125, 250, 375, and 500 mg dm-3) and with four blocks. Irrigation was performed with a semi-automated drip irrigation system with soil moisture monitoring by the Diviner 2000 ® capacitance probe. The assessed variables in fruits were longitudinal and transversal diameter and pulp thickness, fruit shape index, total soluble solids (SS), titratable acidity (TA), the SS/TA ratio, and vitamin C. The data were submitted to statistical analyses at 5% probability error, with analysis of variance by the F-test and polynomial regression. Fruit size presents a reduction as water availability decreased. The total soluble solids have a higher concentration at a potassium dose of 326 mg dm-3. The quality of cherry tomato fruits cultivated in an Oxisol is influenced by water availability and potassium doses.
Safflower crops is usually intended for production of seeds to oil extraction. The objective of this work was to evaluate the chlorophyll index, biometric characteristics and water use efficiency of safflower plants grown under different nitrogen and potassium rates and controlled soil water tension. The experiment was conducted in a greenhouse, in pots containing 8 dm3 of a Oxisol. A complete randomized block experimental design in a 5x5 factorial arrangement was used, with four replications, consisting of five nitrogen rates (0, 60, 120, 180 and 240 mg dm-3) and five potassium rates (0, 50, 100, 150 and 200 mg dm-3). The safflower number of leaves, stem diameter, chlorophyll index, number of capitula, shoot, root and total dry weights, water consumption and water use efficiency were evaluated. Data were subjected to analysis of variance (F test) at 5% of probability and to polynomial regression. The nitrogen and potassium fertilization, as independent factors, affected the safflower plants. The chlorophyll index, biometric characteristics and water use efficiency of safflower showed better responses under nitrogen rates of 82 to 168 mg dm-3. The responses of chlorophyll index, biometric characteristics and water use efficiency of safflower increased 10 to 60% with potassium fertilization.
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