<b>The use of photothermal quotient and frost risk to identify suitable sowing dates for wheat</b> doi: 10.4025/actasciagron.v36i1.14854

Abstract

The potential yield of wheat is mainly determined by temperature, solar radiation and the photothermal quotient. The objective of this study was to determine the temporal and spatial variability of the photothermal quotient and the frost risk to identify suitable sowing dates for wheat in Parana State, Brazil. The results showed that the photothermal quotient has greater spatial variability than temporal variability. The sowing date affects crop conditions that can in turn affect yield. However, the photothermal quotient and frost risk fluctuate differently in different Value for Cultivation and Use (VCU) regions. The regions VCU 1 and VCU 2 showed greater temporal variability of the photothermal quotient. The photothermal quotient ranged from 1.5 to 2.0 MJ m -2 day ºC in VCU 1, from 1.1 to 1.5 MJ m -2 day ºC in VCU 2 and from 1.0 to 1.2 MJ m -2 day ºC in VCU 3. Sowing performed in June provided the greatest photothermal quotient in all VCU regions. However, June sowing increased the frost risk in VCU 1. Thus, the sowing date can be used as a management tool for the attainment of higher yield in wheat.Uso do quociente fototermal e risco de geadas na identificação de época de semeadura adequadas em trigo RESUMO. O potencial de rendimento de grãos em trigo varia, principalmente, em função da temperatura, radiação solar e do quociente fototermal. O objetivo foi estudar a variabilidade temporal e espacial do quociente fototermal (QF) e o risco de geadas visando identificar épocas de semeadura para a cultura do trigo que propicie o maior rendimento de grãos no estado do Paraná, Brasil. Os resultados demonstraram que há maior variabilidade do QF no espaço em relação ao tempo. A época de semeadura afeta as condições de crescimento da cultura, podendo incrementar o rendimento de grãos. Entretanto, o QF e o risco de geadas variam conforme a região de VCU. As regiões de VCU 1 e 2 apresentaram a maior variabilidade temporal do QF. A variação temporal para a região de VCU 1 ficou entre 1,5 a 2,0 MJ m -2 dia ºC (VCU 1), 1,1 a 1,5 MJ m -2 dia ºC (VCU 2) e 1,0 a 1,2 MJ m -2 dia ºC. Em todas regiões de VCU, semeaduras realizadas no mês de junho proporcionam o maior valor de QF. Entretanto, há elevado risco de geadas na região de VCU 1 quando a semeadura ocorre em junho. Assim, a época de semeadura pode ser uma importante ferramenta no manejo para alto rendimento de grãos em trigo.Palavras-chave: Triticum aestivum (L.), potencial de rendimento, radiação solar. 100Silva et al.

Environment-specific selection to identify high yielding wheat genotypes and response to fungicide application

“…These sites are located at altitudes higher than 1.000 m (Table 1), submitting the wheat crop to mild temperatures throughout its cycle (Figure 1), which, combined with the greater availability of incident solar radiation, results in a high photothermal coefficient (PC -relationship between solar radiation and temperature) (Cunha et al 2005;Silva et al 2014). Sites with high PC allow the elongation of growth subphases and consequently greater differentiation of yield components (Fischer, 1985;Gaju et al 2009).…”

Meteorological conditions and their associations with the productive performance of wheat

“…The productivity potential of the wheat crop indicates a relationship existing between the number of spikes, number of spikelets per spike, grain mass and hectoliter mass. The relationship between air temperature, solar radiation, quotient phototermal (PQ), photoperiod and precipitation may change the photosynthetic production in each of the stages (Silva et al, 2014;Lizana and Calderini, 2012). The PQ was determined according to the model proposed by Fischer (1985), where PQ = RS/(Tmed-Tb).…”

“…Here, PQ is the daily photothermal quotient (MJ m -2 day °C), RS is the global solar radiation (MJ m -2 day), Tmed is the mean daily temperature (°C) and Tb is the basal temperature. This quotient photothermal can be used to predict or explain wheat production (Kumar et al, 2016) and frost risk to identify suitable sowing dates for wheat (Silva et al, 2014), estimation of wheat grain yield (Ratjen et al, 2012). The PQ can be used to identify sowing times and regions that maximize grain yield potential (Nalley et al, 2009;Silva et al, 2014).…”

“…This quotient photothermal can be used to predict or explain wheat production (Kumar et al, 2016) and frost risk to identify suitable sowing dates for wheat (Silva et al, 2014), estimation of wheat grain yield (Ratjen et al, 2012). The PQ can be used to identify sowing times and regions that maximize grain yield potential (Nalley et al, 2009;Silva et al, 2014). The sensitive stages of wheat to temperature and water stress were calculated using quotient photothermal in Australia (Dreccer et al, 2018).…”

“…Fischer (2016) investigated the relationship between the duration of the vegetative period (sowing to the anthesis) and the productivity components in semidwarf wheat cultivars in Mexico using the PQ. Therefore, further research is crucial to understand the physiological, morphological and productive behaviors of the wheat cultivars and their responses to a variety of combinations of temperature, solar radiation and precipitation (Silva et al, 2014). However, none of the recent studies evaluated the relationship between the photothermal quotient and production of spring wheat cultivars under the climatic conditions of Santa Maria, Rio Grande do Sul.…”