Comparação entre métodos de estimativa da evapotranspiração de referência (ETo) em regiões citrícolas paulistas

As regiões escolhidas para o estudo são importantes no cenário citrícola irrigado, tanto em expansão quanto em atuação. Os dados meteorológicos utilizados para as estimativas são integrantes do banco de dados climáticos do software IRRIPLUS®. Com este software, estimou-se a evapotranspiração de referência (ETo) diária, utilizando as metodologias propostas por Penman-Monteith (EToPM), Hargreaves & Samani (EToHG) e Blaney-Criddle-FAO (EToBC), para o período de um ano. O objetivo deste estudo foi comparar os métodos de estimativa com EToPM, utilizando parâmetros de regressão (β0, β1), coeficiente de determinação (r²), e correlação (r), estimativa do erro-padrão (SEE), índices de concordância (d) e confiança (c). Os resultados indicam tendência de EToHG à superestimativa dos valores de ETo, exceto na região de Jaú, e subestimativa por EToBC, para todas as regiões estudadas. Nos valores mensais de ETo, os três métodos apresentam a mesma distribuição. O método de EToHG apresenta-se como uma excelente alternativa na estimativa de consumo de água pela cultura.The chosen regions for this study are important in the irrigated citrus context both for its expansion and performance. Meteorological data used for estimates are components of the software IRRIPLUS® climatic database. Using this software, the daily reference evapotranspiration (ETo) was estimated for one-year period, applying proposed methodologies by Penman-Monteith (EToPM), Hargreaves & Samani (EToHG), and Blaney-Criddle-FAO (EToBC). The objective of this study was to compare EToPM estimate methods using regression parameters (β0, β1), determination coefficient (r²), correlation coefficient (r), standard error estimation (SEE), agreement index (d), and confidence index (c). The results indicated an EToHG tendency to overestimate ETo values, except for Jaú region, and an EToBC underestimate for all studied regions. All methods show the same distribution for monthly ETo values. The EToHG method is an excellent alternative for estimating the crop water consumption

Produtividade e qualidade de tubérculos de batata sob diferentes regimes de irrigação por aspersão convencional

O sistema de irrigação por aspersão convencional é muito utilizado na suplementação de água na cultura da batata. Pressionado, devido à baixa eficiência de aplicação de água, este têm sido substituído pela irrigação por pivô central e localizada, objetivamente mais eficiente. A adoção de sistemas mais eficientes a programas de manejo de irrigação podem aumentar a eficiência do uso de água da batateira. Diante disso, o presente trabalho objetivou a avaliação do efeito de diferentes lâminas e regimes de irrigação no cultivo de batata durante a estação outono/inverno de 2007, na região Sul do estado de Minas Gerais. O experimento foi conduzido sob delineamento estatístico de blocos casualizados, com parcelas subdivididas e quatro repetições. Nas parcelas as duas frequências de irrigação [F4(quatro dias) e F6(seis dias)], e nas subparcelas as quatro lâminas de irrigação em função do percentual da irrigação total necessária (ITN) [L1: 0,8 ITN (80%); L2: 1,00 ITN (100%); L3: 1,10 ITN (110%) e L4: 1,25 ITN (125%)]. As variáveis qualitativas foram avaliadas pelo teste t, com nível de probabilidade (≤10%) e análise de regressão, considerando os valores dos coeficientes de regressão (R²). O ciclo total foi de 119 dias com evapotranspiração média de 181,0 a 186,4 mm. As menores lâminas aplicadas foram 129,5 mm e 133,3 mm em L1, nas frequências de 4 e 6 dias e as maiores 203,4 mm e 209,3 mm em L4 para as frequências de 4 e 6 dias, respectivamente. As maiores produções de batata graúda ocorreram nas lâminas de irrigação de 0,99 e 1,05 ITN para as frequências F4 e F6. A maior produção total foi obtida em F6, com a lâmina de 1,06 ITN. O maior valor de uso eficiente de água foi de 38,05 kg de tubérculo m-3 de água, obtido com a combinação de tratamentos F6/L2 e o menor 32,89 tubérculo m-3 de água na combinação F4/L1.The conventional sprinkler irrigation system is widely used in water supplementation in the potato crop. This is pressed due to the low efficiency of water application, so it has been replaced by central pivot and trickle irrigation, which is more efficient. The adoption of more efficient systems for irrigation management programs can increase the efficiency of water use on potato crop. In view of this, the study aimed to evaluate the effect of different water blades and irrigation regimes on potato cultivation during the fall/winter of 2007, in the southern region of Minas Gerais state, Brazil. The experiment was conducted in a randomized block experimental design with split plots and four replications. In the plots two irrigation frequencies [F4 (four days) and F6 (six days)], and in the subplots the four water irrigation levels were evaluated, based on the percentage of total irrigation necessary (ITN) (L1: 80% ITN, L2: 100% ITN, L3: 110% ITN and L4: 125 ITN). Qualitative variables were analyzed by t test with a probability level (≤10%) and regression analysis, considering the values of the regression coefficients (R²). The total cycle was 119 days with average evapotranspiration from 181.0 to 186.4 mm. The lower water blades 129,5 mm and 133,3 mm were applied in the treatment L1, in the frequency 4 and 6 days and the higher water blades 203.4 mm and 209.3 mm in the treatment L4, in the frequency 4 and 6 days respectively. The highest yield of great tubers production occurred in water blades of 0.99 and 1.05 ITN and in the frequency F4 and F6. The highest production was obtained in F6, with the water blade of 1.06 ITN. The highest value of efficient water use was 38.05 kg of tuber m-3 of water, obtained with the combination of treatments F6/L2 and the lowest value 32.89 kg of tuber m-3 of water in the combination F4/L1

Performance of drippers in two filtering systems using sewage treatment effluent

ABSTRACT The objective of this study was to evaluate the performance of three models of drippers using treated sewage effluent, pure and diluted, and two types of filters, screen and disc. The treated sewage effluent used in the experiment was collected from the city’s treatment plant. The experiment included 12 lateral lines with three types of emitters to apply pure (100%) and diluted (50%) effluent filtered by screen and disc filters. The combination of those factors set the treatments: T1 (50% effluent diluted in fresh water filtered by a screen filter); T2 (50% effluent diluted in fresh water filtered by a disc filter); T3 (pure effluent filtered by a screen filter); T4 (pure effluent filtered by a disc filter). The results showed that the flat type emitter is less sensitive to clogging, the disc filter is the most suitable to prevent clogging and the use of pure or diluted sewage effluent increases the drippers’ flow rate coefficient of variation

HIGH PRECISION WEIGHING LYSIMETERS FOR EVAPOTRANSPIRATION MEASUREMENTS OF SUGARCANE PRE-SPROUTED PLANTLETS

<div><p>Abstract Sugarcane pre-sprouted plantlets (PSP) production system is an innovative method to enhance crop multiplication rate. Determination of crop evapotranspiration (ETc) is crucial for water requirement identification throughout the plant cycle for irrigation management. ETc can be satisfactorily measured by weighing lysimeters. The objective of the study was to construct and calibrate three low-cost weighing lysimeters to measure ETc of PSP. The built lysimeters had 0.6909 m2 area (1179 mm × 586 mm), with 400 mm depth supported by 3 load cells. Lysimeters calibration showed excellent precision measurements, due to high linear correlation (R2 = 1.0000) between electric signal and equivalent mass, high accuracy, confirmed by mean absolute error between 0.0272 and 0.0382 mm, mean square error between 0.0011 and 0.0024 mm2 and Willmott's index of agreement (d) equal to unit. Maximum hysteresis (0.1951 mm) and hysteresis at full scale (0.4492%) did not compromise the evaluations. Daily ETc measurements showed variation of 0.27 mm among lysimeters and were coincident with daily course of reference evapotranspiration (ETo). The cost of the equipment was low, except for the data acquisition system. Therefore, lysimeters presented low cost and were adequate to measure ETc of PSP in greenhouse-grown.</p></div