Production and water-use efficiency of Megathyrsus maximus cv. Mombaça "Guinea grass" under nitrogen and boron doses / Produção e eficiência do uso da água de Megathyrsus maximus cv. Mombaça "Guinea grass" sob doses de nitrogênio e boro

Brazilian cattle production is mainly conducted with the use of cultivated or native forages, which is considered one of the most efficient ways of production. In this sense, this study aimed to evaluate the production and water-use efficiency of Guinea grass under different associations between nitrogen and boron doses, as well as different regrowth cycles. The experiment field (22°42'14.6'' S, 47°37'24.1'' W, and 569-m altitude) has a regional climate classified as Cwa, which stands for a humid subtropical climate. The experimental design was randomized blocks, with a 4×4×11 factorial arrangement consisting of boron (0, 0.181, and 0.363 kg ha−1 cycle−1) and nitrogen (22.7, 45.5, 68.2, and 90.9 kg ha−1 cycle−1) fertilizations, plus 11 regrowth cycles and 4 replications. The pasture of Mombaça "Guinea grass" (Megathyrsus Maximus Syn. Panicum Maximum) was irrigated by a sprinkler system. Unlike boron, nitrogen positively influenced forage production. The cycles had a strong influence on production, with winter cycles being the least productive compared to the others.(AU)

A produção bovina brasileira é feita principalmente com o uso de forragens cultivadas ou nativas, que é considerada umas das maneiras mais eficiente de produção. Nesse sentindo, teve-se por objetivo avaliar a produtividade e produtividade da água do capim Mombaça com diferentes combinações de nitrogênio e boro em diferentes ciclos de rebrota. O campo experimental (22°42'14,6'' S e 47°37'24,1'' O, com altitude de 569 m) possui um clima regional classificado como tipo Cwa - Subtropical ou tropical de altitude. O delineamento experimental utilizado foi um fatorial 4×4×11, sendo 2 formas de adubação: boratada foram adotados os níveis de 0; 0,181 e 0,363 kg ha−1 ciclo−1 e a adubação nitrogenada com níveis 22,7, 45,5, 68,2 e 90,9 kg ha−1 ciclo−1 com 11 ciclos de rebrota, e 4 repetições. A pastagem utilizada foi o capim Mombaça "Guinea grass" (Megathyrsus Maximus syn. Panicum Maximum) em sistema irrigado por aspersão. Durante o período avaliado observou-se que o nitrogênio influenciou positivamente a produção forrageira, enquanto o boro não influenciou a produção forrageira. Os ciclos tiveram forte influência na produção, sendo que os ciclos de inverno foram os menos produtivos comparados aos demais.(AU)

Crop coefficients of tropical forage crops, single cropped and overseeded with black oat and ryegrass

Crop coefficient (Kc) is the ratio between crop evapotranspiration (ETc) and reference evapotranspiration (ETo), representing the phenological effects on crop water consumption. Kc is fundamental to estimating ETc by agrometeorological methods. This research study aimed to determine Kc and ETc values for Guinea grass (Megathyrsus maximus cv. Mombaça) and Bermuda grass (Cynodon spp.), both single cropped for one year and overseeded with black oat (Avena strigosa) and ryegrass (Lolium multiflorum) during fall/winter. The experiment in the field comprised four plots, two for each tropical forage, with and without overseeding. At the center of each plot, there was a weighing lysimeter with an automated system for data collection. ETc was measured daily over four seasons following the lysimetric method; ETo was calculated using the Penman-Monteith equation. ETc and ETo values were used to estimate Kc values. The single cropped Guinea grass showed the highest values for ETc, with mean ETc and Kc of 3.99 mm d–1 and 1.07, respectively. The single cropped Bermuda grass showed ETc and Kc values of 3.57 mm d–1 and 0.96, respectively. The results of paired t-testing for Kc showed no significant differences (p = 0.05) between single cropped and intercropped for both Guinea grass and Cynodon spp. During winter, intercropped Guinea grass did not show an ETc significantly higher than single cropped Guinea grass, with mean Kc values 0.98 for intercropped and 1.10 for single cropped. Similarly, Bermuda grass did not show significant differences between mean Kc values for intercropped (1.02) and single cropped (1.00).(AU)

Crop coefficients of tropical forage crops, single cropped and overseeded with black oat and ryegrass

Crop coefficient (Kc) is the ratio between crop evapotranspiration (ETc) and reference evapotranspiration (ETo), representing the phenological effects on crop water consumption. Kc is fundamental to estimating ETc by agrometeorological methods. This research study aimed to determine Kc and ETc values for Guinea grass (Megathyrsus maximus cv. Mombaça) and Bermuda grass (Cynodon spp.), both single cropped for one year and overseeded with black oat (Avena strigosa) and ryegrass (Lolium multiflorum) during fall/winter. The experiment in the field comprised four plots, two for each tropical forage, with and without overseeding. At the center of each plot, there was a weighing lysimeter with an automated system for data collection. ETc was measured daily over four seasons following the lysimetric method; ETo was calculated using the Penman-Monteith equation. ETc and ETo values were used to estimate Kc values. The single cropped Guinea grass showed the highest values for ETc, with mean ETc and Kc of 3.99 mm d–1 and 1.07, respectively. The single cropped Bermuda grass showed ETc and Kc values of 3.57 mm d–1 and 0.96, respectively. The results of paired t-testing for Kc showed no significant differences (p = 0.05) between single cropped and intercropped for both Guinea grass and Cynodon spp. During winter, intercropped Guinea grass did not show an ETc significantly higher than single cropped Guinea grass, with mean Kc values 0.98 for intercropped and 1.10 for single cropped. Similarly, Bermuda grass did not show significant differences between mean Kc values for intercropped (1.02) and single cropped (1.00).

Comparison of water consumption estimates for tropical and winter forages by FDR probes and weighing lysimeters / Consumo de água em forrageiras tropicais e de inverno obtido por sonda FDR e lisímetros de pesagem

Soil moisture determination is essential for a good use of available water resources. In this regard, the use of frequency domain reflectometry (FDR) probes has as advantages mobility and practicality in relation to lysimeters. The experiment was carried out between April and June 2016 at the Luiz de Queiroz College of Agriculture (ESALQ/USP), located in Piracicaba, SP at the geographical coordinates 22°42′14.6″ S and 47°37′24.1″ W and altitude of 546 m. This study aimed to assess these FDR probes to estimate water consumption in comparison to measurements by weighing lysimeters (ETcLys) and reference evapotranspiration (ETo) in Mombaça and Bermuda grass pastures under single cultivation and overseeded with oat and ryegrass. Soil moisture was assessed daily by FDR probes by estimating crop evapotranspiration (ETcFDR probe) from soil water balance calculation, which was correlated with ETcLys and ETo (Penman-Monteith, FAO 56). For all treatments, FDR probes presented the highest water consumptions when compared to the other two evapotranspiration methods, with accumulations of 126.5 and 125.6 mm for single and overseeded Mombaça grass, respectively. For Bermuda grass, water consumption was 123.4 mm in the single cultivation and 128.5 mm when overseeded. The method of estimating evapotranspiration by FDR probes showed good correlations with ETo and ETcLys.(AU)

A determinação da umidade do solo é preponderante para o bom uso dos recursos hídricos disponíveis. Neste aspecto, as sondas de Reflectometria no Domínio da Frequência (FDR) tem a vantagem da mobilidade e praticidade em relação aos lisímetros. O experimento foi conduzido entre abril e junho de 2016 na Escola Superior de Agricultura “Luiz de Queiroz” (ESALQ/USP), localizada em Piracicaba, SP nas coordenadas geográficas 22°42′14.6″ S e 47°37′24.1″ O e altitude de 546 m. O objetivo desse trabalho foi avaliar o uso de sonda FDR para estimativa do consumo de água em relação a medidas obtidas através de lisímetros de pesagem (ETcLis) e da evapotranspiração de referência (ETo) em pastagens de capim Mombaça e Cynodon em cultivos exclusivos e sobressemeados com aveia e azevém. A umidade de solo foi diariamente avaliada pela sonda FDR estimando a evapotranspiração de cultura (ETcsonda FDR), a partir do cálculo de balanço hídrico no solo, que foi correlacionada com a ETcLis e a ETo (Penman-Monteith - FAO 56). A sonda FDR apresentou para todos os tratamentos os maiores consumos em relação aos outros dois métodos de evapotranspiração, com acúmulos durante o ciclo de 126,5 mm e 125,6 mm, no Mombaça exclusivo e sobressemeado, respectivamente. No Cynodon spp., o consumo foi de 123,4 mm no cultivo exclusivo e 128,5 mm no sobressemeado. O método de estimativa de evapotranspiração pela sonda FDR apresentou boas correlações com a ETo e ETcLis.(AU)

Comparison of water consumption estimates for tropical and winter forages by FDR probes and weighing lysimeters / Consumo de água em forrageiras tropicais e de inverno obtido por sonda FDR e lisímetros de pesagem

Soil moisture determination is essential for a good use of available water resources. In this regard, the use of frequency domain reflectometry (FDR) probes has as advantages mobility and practicality in relation to lysimeters. The experiment was carried out between April and June 2016 at the Luiz de Queiroz College of Agriculture (ESALQ/USP), located in Piracicaba, SP at the geographical coordinates 22°42′14.6″ S and 47°37′24.1″ W and altitude of 546 m. This study aimed to assess these FDR probes to estimate water consumption in comparison to measurements by weighing lysimeters (ETcLys) and reference evapotranspiration (ETo) in Mombaça and Bermuda grass pastures under single cultivation and overseeded with oat and ryegrass. Soil moisture was assessed daily by FDR probes by estimating crop evapotranspiration (ETcFDR probe) from soil water balance calculation, which was correlated with ETcLys and ETo (Penman-Monteith, FAO 56). For all treatments, FDR probes presented the highest water consumptions when compared to the other two evapotranspiration methods, with accumulations of 126.5 and 125.6 mm for single and overseeded Mombaça grass, respectively. For Bermuda grass, water consumption was 123.4 mm in the single cultivation and 128.5 mm when overseeded. The method of estimating evapotranspiration by FDR probes showed good correlations with ETo and ETcLys.

A determinação da umidade do solo é preponderante para o bom uso dos recursos hídricos disponíveis. Neste aspecto, as sondas de Reflectometria no Domínio da Frequência (FDR) tem a vantagem da mobilidade e praticidade em relação aos lisímetros. O experimento foi conduzido entre abril e junho de 2016 na Escola Superior de Agricultura “Luiz de Queiroz” (ESALQ/USP), localizada em Piracicaba, SP nas coordenadas geográficas 22°42′14.6″ S e 47°37′24.1″ O e altitude de 546 m. O objetivo desse trabalho foi avaliar o uso de sonda FDR para estimativa do consumo de água em relação a medidas obtidas através de lisímetros de pesagem (ETcLis) e da evapotranspiração de referência (ETo) em pastagens de capim Mombaça e Cynodon em cultivos exclusivos e sobressemeados com aveia e azevém. A umidade de solo foi diariamente avaliada pela sonda FDR estimando a evapotranspiração de cultura (ETcsonda FDR), a partir do cálculo de balanço hídrico no solo, que foi correlacionada com a ETcLis e a ETo (Penman-Monteith - FAO 56). A sonda FDR apresentou para todos os tratamentos os maiores consumos em relação aos outros dois métodos de evapotranspiração, com acúmulos durante o ciclo de 126,5 mm e 125,6 mm, no Mombaça exclusivo e sobressemeado, respectivamente. No Cynodon spp., o consumo foi de 123,4 mm no cultivo exclusivo e 128,5 mm no sobressemeado. O método de estimativa de evapotranspiração pela sonda FDR apresentou boas correlações com a ETo e ETcLis.