Climatic Factors Affecting Maize Grain Yield in Different Growing Areas of the Philippines

Seasonal climate variation is one of the problems faced by Filipino maize farmers, due to varying climatic elements such as solar radiation, rainfall, relative humidity, and air temperature. This study determined the seasonal productivity of selected maize varieties in the major growing areas in the Philippines, and identified the yield-limiting climatic factors specific to location and growing season. Grain yield, covering two wet and dry seasons (2016-2018) from seven field trials (representing 3 climatic types) of the National Corn Testing (NCT) were used in the study. Climatic data (2016-2018) were gathered from the PAGASA weather station nearest to the trial site. Significant variation in the monthly solar radiation, rainfall, relative humidity, and the mean temperature (309.1-786.6 MJ m(2), 19.9-667.5 mm, 64.3-91.4%, 18.8-35.8 degrees C, respectively) were observed across seven locations. Relative humidity significantly varied by season. Mean temperatures below 30 degrees C and mean relative humidity of more than 80% were observed across locations. Grain yield variations due to season (3394.8-9985.1 kg ha(-1)), location (1382.4-11931.4 kg ha(-1)), and climate type (3052.1-8650.9 kg ha(-1)) were highly significant. Grain yield was significantly affected by cumulative solar radiation specific to variety and season. Solar radiation use efficiency (SRUE) during wet season was highly variable, and consistently higher SRUE was observed during dry season. Grain yield of the three varieties were correlated with growing degree days (GDD) during wet and dry seasons (r = 0.28, 0.29, and 0.33). The grain yield of 30B80 was more affected by cumulative solar radiation (r = 0.46), while USM Var10 (r = 0.33) was more associated with GDD. Solar radiation and minimum temperature positively affect the grain yield of variety 30B80, while maximum temperature and relative humidity had negative effect. Solar radiation was the major yield-limiting factor for variety 30B80, whereas maximum temperature and solar radiation increased the grain yield of IPB Var11. The major yield-limiting factor for IPB Var11 was relative humidity. Grain yield of USM Var10 increased with solar radiation, while relative humidity and maximum temperature had negative effect. Location was the maize yield-limiting factor, whereas relative humidity affected the grain yield of USM Var10 dominantly. Significant seasonal climate variation can be observed in the major maize growing areas resulting in different seasonal productivity, while solar radiation and relative humidity are the major yield-limiting climatic factors. Moreover, the hybrid variety, 30B80, can be recommended for dry season in Batac, Tupi, and Baybay; wet season in Ubay; and both wet and dry season in Maramag, Kabacan, and Ilagan as a high-yielding maize variety.