Drought index
Based on Table 3, level of drought during the strong El Nino climate anomaly in 1997-1998, 2002-2003 and 2015-2016 had strong (S) to moderate (M) drought levels with an average number of months of 9, 7 and 13 months. The level of drought in the year of the moderate El Nino climate anomaly in 2009-2010 had a moderate (M) to strong (S) level of drought with an average number of months of 6 months. The occurrence of drought levels in strong and moderate Elnino years is dominated by moderate (M) to strong (S) drought levels. This has the potential to influence the pattern and timing of maize planting, thereby potentially affecting maize productivity. On the other hand, in a normal year, the drought level is dominated by a weak level (W). The occurrence of climate anomalies since more than 100 years ago shows that the average duration of El-Nino events is around 8.5 months with a range of 4 - 12 months, while La Nina months range from 5 - 15 months. The El-Nino climate anomaly causes changes in the delay in planting time which will impact the following year’s planting season. El-Nino 1997 shifted the 1997-1998 planting time by 2-3 months (6-9 days) which also significantly affected subsequent planting patterns
Irawan (2006a);
Garcia et al., (2009) stated that there are main impacts of climate variability, especially during the transition period, in the form of soil water content with different conditions, erratic soil temperatures that trigger the size of evaporation and transpiration, which have the potential to disrupt the productivity of maize plants.
Hassanli et al., (2009) stated that implementing an appropriate irrigation schedule, especially in sensitive and critical maize development phases, is necessary for efficient water use.
Based on Table 3, pattern of repeated occurrence of drought climate anomalies or El Nino phenomenon ranges from 5 to 6 years, namely 1997-1998, 2002-2003, 2009-2010 and 2015-2016. The frequency of El Nino events tends to increase with longer duration, greater levels of climate anomalies and shorter event cycles. This climate anomaly causes a decrease in rainfall and the availability of irrigation water, which in turn has implications for a decrease in food production of 3.06 per cent for each El Nino event. On the other hand, La Nina events tend to be followed by increased rainfall and stimulate an increase in food production of 1.08 percent. The impact of El Nino year on corn is a decrease in production of 11.93% and in La Nina year there was an increase in production of 3.92% (Table 4). The decline in food production due to the El Nino climate anomaly and the increase in food production due to La Nina was highest in maize production (
Irawan, 2006a). This shows that maize production is most sensitive to climate anomaly events.
Based on Table 5, from 1996 to 2001 the harvested area and corn production were still very low compared to 2002 to 2016. This was because from 2002 to 2014 Gorontalo area became an autonomous provincial region with the main Corn Agropolitan program. This program was able to encourage an increase in harvested area and corn production from 2002 to 2014, but there was a decrease in production in the strong and moderate El Nino climate anomaly years, namely 1997-1998, 2002-2003, 2009-2010 and 2015-2016. This is in accordance with coefficient of reduction in corn production which is categorized as vulnerable to moderate to a decline in production due to El Nino climate anomaly. This is because during El Nino climate anomaly, such as in 1997, there was a water deficit for 6 months from June to November (Table 6). According to
Lesilolo et al., (2024) food plants with relatively shallow roots are plants most sensitive to water shortages when El Nino occurs. On the other hand, when La Nina lasts, the period of water availability on agricultural land will increase, thereby lengthening planting season and increasing planting intensity and production. However, excess water during La Nina needs to be anticipated, especially on land that is sensitive to inundation.
Kaur et al., (2021) states that high temperatures can increase rate of evapotranspiration thereby increasing plant stress factors in the form of water stress accompanied by nutrient stress which will result in stunted growth and low corn seed production.
In La Nina climate anomaly years, namely 2007-2008 and 2013-2014, there was an increase in corn production which reached 753,598 tons/year due to an increase in planting intensity caused by increased water supply for plants. This is indicated by coefficient of reduction in corn production which is categorized as very resistant to decreasing production. This is because in La Nina climate anomalies such as in 1999 there was a water surplus for 10 months which triggered an abundance of water availability during planting period of one year (Table 7). According to
Nangimah et al., (2018) the positive impact of La Nina climate anomaly in form of increased rainfall during dry season can trigger an increase in planting intensity, especially in areas with a dry climate. Through Corn Agropolitan Program, Gorontalo provincial government is also implementing anticipatory strategies when El Nino and La Nina climate anomalies occur in form of using varieties that are resistant to drought and flooding, providing water pumps without engines, repairing irrigation channels and creating reservoirs in upstream areas as temporary water storage areas.
Singh et al., (2017) suggests that climate anomalies can be facilitated by improving irrigation, developing plant varieties that require less water and heat resistant, using minimum tillage for practices to increase soil nutrient and moisture retention as well as regulating changes in planting and harvest times.
Potential accumulation of water loss
Based on Fig 1a and 1b, in the years of strong La Niño climate anomalies in 1999 and 2007 and 2008, the data shows that there was no accumulation of potential water loss, whereas in the years of strong El Nino climate anomalies, 1997-1998, there was an accumulation of potential water loss of 1869 mm. In 2015 and 2016 it was 1861 mm. In the moderate El Nino climate anomaly in 2002-2003 it was 2190 mm and in 2009-2010 it was 1392 mm. This triggers water stress and ultimately a water deficit due to extreme drought which can affect the productivity of maize plants.
Igbadun et al., (2007) states that maize productivity is related to water availability which influences a number of subjects such as the maize varieties cultivated, soil water content per plant (deficit or surplus) and the irrigation technology applied. (Kheira, 2009) stated that the influence of water deficit in reducing maize seeds and crop biomass. In this study, it was found that water stress can affect components of maize production such as cob size, number of kernels per cob and plant seed weight.
a
b
Based on Fig 1a and 1b, in strong El Nino climate anomaly years, namely in 1997-1998, 2002-2003, 2015-2016 and moderate El Nino in 2009-2010, there was a large accumulation of potential loss due to the actual evapotranspiration accumulation rate (ETa). greater than monthly rainfall. This has an impact on reducing soil moisture due to large evapotranspiration rates and ultimately the water available to plants decreases which has an impact on plant water stress.
Ko and Piccinni (2009) stated that treatment with a plant evapotranspiration rate (ETc) of 75% resulted in the reduction of maize seeds and triggered an increase in water use efficiency of 1.6 g m-2 mm-1.
Payero et al., (2009) stated that the water available in the soil is not enough to meet the water needs of maize plants during the planting period and that appropriate irrigation times are needed by considering the plant’s evapotranspiration rate and the efficiency of plant water use to maximize maize production. (
Krishna, 2019) stated that availability of groundwater on a spatial and temporal scale is necessary to maintain soil moisture which acts as a water source to meet plant water needs and crop water needs that are not met through irrigation sources. The evapotranporation process is main source of water loss that flows to the plant root zone which represents water needs from the atmosphere.