Land management without burning and corn productivity enhancement during long dry season in West Kalimantan, Indonesia

In long dry season (El Nino), thousand hectares of agricultural land in Indonesia to experience drought, and sometimes wildfires occur naturally. Land management without burning and environmentally friendly agricultural cultivation needs to be done in the long dry season. It is not recommended to use crop residue that is burned on the land, since the residue can be composted into organic matter which later is returned to the agricultural land as organic fertilizer. Currently, about 40% farmers use local corn varieties. Corn farming lands in Indonesia are generally deficient in nitrogen. Consequently, drought tolerant new superior corn varieties complemented with right dose fertilizer based on plant needs, especially N fertilizer, are needed to increase corn productivity in the dry season. This research aimed to ascertain adaptive hybrid corn varieties and right N fertilizer rate on the growth and productivity of corn planted on the land without burning. The experimental design was Randomized Complete Block Design consisting of 2 factors. The first factor was corn varieties, namely Bima 19, Nasa 29, and JH 21; whereas, the second factor was N fertilizer rate, namely 64, 86.5, 109, and 131.5 kg ha-1. The combination of the two factors consisted of 12 treatments, which were repeated 3 times. The results showed that there was an interaction between the new high yielding varieties and the N fertilizer rate on corn productivity. Greater yields were performed in Bima 19 with N rate of 109 and 131.5 kg ha-1 and Nasa 29 with N rate of 131.5 kg ha-1 i.e., 8.45, 7.94, and 8.04 t ha-1, respectively. Bima 19 and Nasa 29 are drought tolerant high yielding corn varieties.


Introduction
Forest and land fire disasters in several regions in Indonesia almost every year occur during the long dry season (El Nino) as shown in figure 1. Hotspot detection using VIIRS and MODIS sensors on polar satellites (NOAA20, S-NPP, TERRA, and AQUA) provides an overview of the locations of Indonesian areas experiencing forest fires.In July 2023, 162 forest fires or hotspots have been detected throughout Indonesia (Figure 1) [1].The distribution of forest fires or hotspots has greatly affected the climate, especially related to land clearing or land preparation for agriculture.
The occurrence of a long drought will have an impact on agricultural sector, such as forest and land fires and lack of water availability for plant growth.This conditions can affect reduced crop yields.In addition, forest and land fires also destroy plant and animal genetic resources.Various efforts have been made by the Indonesian government to prevent and control forest and land fires.One way to prevent forest and land fires, especially on agricultural land, is land clearing and land management without burning, which is environmentally friendly, especially during the long dry season (El Nino).If we look at the derivative products of Himawari-9 Potential Rainfall (Figure 2) [2], the potential for light, moderate, heavy, to very heavy rainfall categories, which is classified based on the relationship between cloud top temperatures and potential rainfall, it is estimated that the Indonesian region will experience a long dry season [2].
Source: Meteorological Climatological and Geophysical Agency, 2023

Figure 2. Himawari-9 Potential Rainfall throughout Indonesia
Upland is defined as a stretch of land that is utilized without flooding, either permanently or seasonally with water sources from rainfall or irrigation water [3].In addition, Soil Survey Staffs also describes upland as an expanse of land that has never been inundated or inundated for a period most of the year.This typology of land can be found from the lowlands (0-700 m asl) to the highlands (>700 m asl) [4].From the above understanding, the types of land use included in the upland group include: rainfed land, dry fields, fields, mixed gardens, plantations, forests, bushes, grasslands, and alang-alang (Imperata cylindrica) grasslands [5,6].
Drylands and rainfed land for agricultural practices are affected by water availability or limited water depending on rainfall.While wetlands for agricultural areas are supported by water availability almost all year round.Understanding drylands and rainfed land management is critical to obtaining higher crop yields and promoting long-term sustainable soil fertility.
Clearing and cultivating land for agriculture is the process of clearing land from trees, stumps, shrubs, and other obstacles for farming.However, in practice, in the field, tree residues, stumps, straws, crop residues, and shrubs resulting from logging are burned in the land without care, this is what causes land fires.Therefore, the technology of agricultural cultivation without burning is needed.This technology, among other things, is by providing decomposer on the remains of cutting and plant straw to make organic compost which can be used as fertilizer for plants.This research provides information on managing and cultivating the land for corn fields without burning the land on rainfed agroecosystem during the dry season in Sungai Kakap Sub District, instead composting the corn straw with a decomposer, and applying as organic fertilizer.
The utilization of high-yielding or superior quality corn seeds is only around 60% of the total planting area [3].Hybrid corn varieties produced by the Indonesian Agency for Agricultural Research and Development are generally multiplied and marketed by the private sectors, which obtain licenses, namely for Nasa 29 by 8 companies and Bima 20 URI by 14 companies [7].High-yielding hybrid corn varieties that have been released have good adaptability; however, not all varieties can grow and develop in various agroecosystems, meaning that each variety will provide optimal results if planted on the appropriate land.Therefore, corn variety testing is still needed to evaluate the response of plants under specific agroecological conditions [8].
Proper application of fertilizer during corn growth can increase yields [9,10,11,12].One of the macronutrients needed by corn plants during their life cycle is nitrogen [13,14].Nitrogen (N) in plants functions as a synthetic material for chlorophyll, protein, and amino acids [15].Nitrogen is absorbed by plants during the growth period until seed ripening, so plants require continuous N availability at all growth stages until seed formation [16,17].N deficiency affects productivity and yield quality; while excess N causes plants to fall over easily, besides being inefficient and having a negative impact on the environment [16,10,11,18,19].Nitrogen is generally mobile; consequently, to reduce N loss due to leaching or evaporation, N fertilizer is applied gradually.
In order to anticipate drought especially in the dry season, corn varieties that are drought tolerant and high-yield potential are needed.Moreover, implementing soil fertility program with N fertilizer management is necessary to ensure good quality and high corn production.Therefore, the purpose of this study was to determine the adaptation of corn varieties and the appropriate N fertilizer rate on the growth and productivity of corn plants by managing land without burning in the dry season.

Study site description
This research was conducted on rainfed fields during the dry season (Juli to October 2019) in Sungai Kakap Sub District, Kubu Raya Regency, West Kalimantan Province, Indonesia.The climate type based on Köppen climate classification scheme is Af (tropical rain forest).Relative humidity is 81.75% with daily temperature around 22.64 to 31.97 o C [20].The Average annual precipitation is 195.32 mm with an average of 255 rainy days yr -1 [20].Based on average temperatures and precipitation data in Sungai Kakap Sub District over 30 years

Materials and cultivation technology
Non-burning land clearing bio-management method was conducted by managing land biophysical resources and biomass.Biological agents such as decomposers was utilized to accelerate decomposition of biomass or in-situ residue from corn straws and shrubs.Biomass or plant residues were not burned in the field but were collected on a plot of 1 x 1 x 1.5 m and composted using decomposer of 0.5 kg M-Dec in 10 L water for 1 ton corn straw.It produced compost 5 t ha -1 that was applied as an organic fertilizer in the raised beds.The ripe compost was brownish black with a temperature around 30 ºC and 40-60% humidity, and it should also not smell bad.
The materials used in this research included high-yielding drought-tolerant corn varieties that were obtained from Indonesian Cereals Research Center.Chicken manure 4 t ha -1 was also applied in the planting hole as ameliorant.Inorganic fertilizers such as P2O5 and K2O were split applied in the rate of 87 and 64 kg ha -1 , respectively, while N fertilizer was added based on the treatment rates.
Land was cultivated with minimum tillage.Corn planting was conducted on raised beds with a width of 4.5 m and a plot length of 10 m.The corn was planted with a spacing of 75 cm x 20 cm for 1 seed per planting hole.Thus, the number of plants between rows was 7 plants and in rows was 50 plants.Planting was conducted using a shovel and after planting, the corn seeds were covered with 50 g of manure per planting hole.Weed control used selective herbicides on 21 days after planting.Other materials used in this field study were chemical pesticides to control pests and diseases.

Design, data, and analysis
This research was arranged in a randomized complete block design experiment with two factors i.e., corn variety and N fertilizer rate.The first factor consisted of three treatments of high-yielding corn varieties, whereas the second factor comprised four treatments of N fertilizer rates, as presented in table 1.All treatment combinations were repeated three times.

Non-burning land clearing bio-management method
Land preparation by field burning of agricultural crop residues is a common, easy, and cheap practices.However, it causes some environmental concern, such as greenhouse gas emission, destroyed soil microorganisms, and soil fertility loss.Plant residues such as corn stalks which are left naturally in the field does take a long time for the decomposition process, which generally it takes about 4 to 5 months.M-Dec decomposer accelerates the composting of corn straw.It only takes around 3-4 weeks with a C/N ratio of 14-15.The advantages of composting straw with a decomposer in land preparation without burning are that it can be performed by farmers easily and inexpensively, the straw does not need to be burned to avoid land fires, it accelerates the composting of organic matter which contains a lot of cellulose from 4 months to 3 weeks, and all the remaining straw after harvesting can be safely returned to the field because it has been composted into organic fertilizer.

Variety and N fertilizer rate on vegetative growth performance of corn plant
The results of the research on anticipation to drought showed that there was no effect of corn variety (Bima 19, Nasa 29, and JH 21) on the vegetative growth, i.e. plant height, cob height, and plant height to cob height ratio (Table 2).The highest N fertilizer rate of 131.5 kg ha -1 N significantly influenced the highest corn plant and cob height compared to the other treatments i.e., 207.69 and 102.04 cm, respectively (Table 2).Whereas, the highest ratio of plant height to cob height was found in N fertilizer rate of 109 kg ha -1 N i.e., 49.87.Nevertheless, there was no difference on the cob height and plant height to cob height ratio in the lower N fertilizer rates of 86.5 and 109 kg ha -1 N compared to the highest N rate of 131.5 kg ha -1 N (Table 2).
Corn plant height is strongly influenced by genetic and environmental factors.Genetic factors are the influence of heredity that is owned by each variety, while the environmental factors are the influences caused by the condition of corn plant location where the corn grows and the environment [23].In relation to the other study, corn cob height without N fertilization is around 62.5-81.8cm; while if added with N fertilization it becomes 83.8-108.0cm [24].
The combination treatments of corn varieties and N fertilizer rates did not affect male and female corn flowering ages that was observed when the corn plants produced 50% flowers (Table 2).Female inflorescences on corn can increase the yield of corn kernels.This is suspected by the length of seed filling period causing a longer and optimal seed filling period [8].That earlier flowering corn causes longer filling of corn kernels [25].

Variety and N fertilizer rate on yield components and yield of corn
The results of the analysis in Table 3 indicated that there was no difference on the cob length of the three corn varieties of Bima 19, Nasa 29, and JH 21.While the longest cob was found on N fertilizer rates of 131.5 and 109 kg ha -1 i.e., 19.03 and 18.32 cm, respectively.The results of the analysis in table 3 showed that JH 21 corn variety had the significantly biggest cob circumference (15.94 cm).Whereas N fertilizer rate treatment of 109 and 131.5 kg ha -1 N influenced the significantly bigger cob circumference i.e., 15.96 and 15.63 cm, respectively.
Data in Table 3 presented there was no influence of the treatments of three corn varieties and N fertilizer rates of 64 to 131.5 kg ha -1 N on the number of kernel rows per cob.Furthermore, there was also no significant effect of corn varieties on the number of kernels per row.While the highest N rate of 131.5 kg ha -1 significantly affected the greater number of kernels per row (32.61 kernels), compared to 64 kg ha -1 N that comprised 29.72 kernels per row.
The significantly greatest number of kernels per cob (435.33 kernels) as presented in table 3 was discovered in Nasa 29.In addition, JH 21 and Bima 19 corn varieties had the significantly higher weight of 1000-kernel i.e., 351.75 and 339.67 g, respectively, compared to Nasa 29 (328 g) (Table 3).
N fertilization treatment significantly affected the greater number of kernels per cob and weight of 1000-kernel, as demonstrated in the N rate of 86.5-131.5 kg ha -1 N (Table 3).Nitrogen fertilizer of 131.5 kg ha -1 N had significantly greater kernels per cob (424.67 kernels), whereas the significantly less kernels per cob was in the N rate of 64 kg ha -1 (380.78).
Higher yield components of corn such as cob length and cob circumference were significantly altered by N fertilizer rates of 109.0-131.5 kg ha -1 N.However, greater yield components of corn such as number of kernels per row, number of kernels per cob, and 1000-kernel weight were shaped by N rates of 86.5-131.5 kg ha -1 N.This result was in concordance with the greater weight of 1000 grains on corn plants with nitrogen fertilization compared with the less weight of 1000 grains without N addition [24].
Long corn cobs have the opportunity to have more kernels, so that they can provide higher yields.The cob length character indicates the seed density and is closely related to the number of seeds per ear [26].The bigger the cob, the bigger the space for the growth and development of corn seeds [23].The longer the corn cob has a direct effect on the number of seeds per cob row.Data in table 4 showed that there was an interaction between the treatments of corn varieties with N fertilizer rates.The highest productivity was Bima 19 variety with N rate of 109 kg ha -1 N (8.45 t ha -1 ) and 131.5 kg ha -1 N (7.94 t ha -1 ) and Nasa 29 variety with N rate of 131.5 kg ha -1 N (8.04 t ha -1 ).Application of 112.5 kg ha -1 nitrogen fertilizer can increase total plant weight by 23.53% compared to the N fertilizer of 22.5 kg ha -1 [27].Linear application of urea up to 300 kg ha -1 can increase yields [28].
The filling of corn cobs is influenced by the supply of nutrients to form and assimilate during the period of growth and cob filling.Corn productivity will increase with sufficient nutrient supply, optimal cob growth and seed filling [28,29].Research about N management from several areas in Indonesia illustrated that N utilization influences higher yields.On Ultisol dry land in Lampung, a nitrogen rate of 45-160 kg ha -1 yielded 4-5 t ha -1 , on Alluvial lowland rice fields in Kediri (East Java) with a nitrogen rate of 225-360 kg ha -1 and in Gowa and Takalar (South Sulawesi) with N fertilization of 270-360 kg ha -1 , the corn yields were around 6-8 t ha -1 , and in South Sulawesi 150-225 kg ha -1 N fertilizer enhanced hybrid corn yield (11-14 t ha -1 ) [30,31,32,33].Genetically, Nasa 29 corn variety has advantages over climate change which is often erratic [34].

Conclusions
Land clearing and soil preparation without burning using a decomposer to make compost from plant residues and corn straw is very effective in preventing land fires and increasing land productivity.It concluded that corn variety of Bima 19 with N fertilizer rates of 109 and 131.5 kg ha -1 N and Nasa 29 variety with 131.5 kg ha -1 N fertilizer had a good adaptation during dry season and produced higher yields.Nasa 29 and Bima 19 had significantly greater number of kernels per cob, whereas the significantly higher 1000-kernel weight was found on JH 21 and Bima 19.N fertilizer rates of 86.5-131.5 kg ha -1 N significantly affected yield components of corn (the number of kernels per cob and the weight of 1000 kernels) and corn productivity.Bima 19 and Nasa 29 are corn varieties that are tolerant to drought in West Kalimantan, Indonesia.

Figure 1 .
Figure 1.Forest fires or hotspots location detected throughout Indonesia

4 of
of hourly weather model simulations, during dry months 1314 (2024) 012012 IOP Publishing doi:10.1088/1755-1315/1314/1/012012May to September there always have less precipitation and the temperature rise compared to the other months, as shown in figure 3 [21].Source: Meteoblue Weather, 2023

Figure 3 .
Figure 3. Average temperatures and precipitation in Sungai Kakap over 30 years (1993-2023) of hourly weather model simulations

Table 1 .
Combination of corn variety and N fertilizer rate as the treatments.

Table 2 .
Effect of corn varieties and N fertilizer rates on vegetative growth of corn plant.
Note: Numbers accompanied by the same letters in the same column are not significantly different based on 5% LSD test; ns = nonsignificant.

Table 3 .
Effect of corn varieties and N fertilizer rates on yield components of corn.
Note: Numbers accompanied by the same letters in the same column are not significantly different based on 5% LSD test; ns = nonsignificant.

Table 4 .
Effect of corn varieties and N fertilizer rates on corn yield.