Effect of different feed nitrogen on nutrient flow, performance, and productivity in the minapadi system

Cultivation with the minapadi method can increase the availability of nutrients and soil organic matter from the decomposition of feed residues and weeds. This system implements environmentally friendly cultivation and creates a sustainable ecosystem because rice plants use fish waste as a source of nutrients, and fish use weeds and pests in rice as a food source. This study aims to find the best feed formula in the minapadi system based on differences in nitrogen content and to analyze the effect of nitrogen from the artificial feed given on nitrogen flow, performance, and productivity in the minapadi system. Using a randomized block design method with four treatments of different feed doses repeated three times to obtain twelve experimental plot units, feed production using local raw materials that are cheap and easy to obtain, soil quality, water, and growth performance are the parameters observed. The results showed that the soil and water quality at the study site was quite good, so the growth performance of rice plants and fish was also good. The treatment of the feed doses given showed that the feed with the highest nitrogen content, namely 9%, gave the best growth performance for rice plants, while 7% nitrogen content gave the best growth for tilapia. The excessive levels of protein are not suitable for fish. However, they are handy for rice plants in the Minapadi system because nutrients that dissolve in water, nutrients from fish feces and urine, and nutrients that are sedimentation on the soil surface, are utilized by rice plants as a nutrient source.


Introduction
As the main crop in Indonesia, rice dominates for cultivation; paddy land was recorded at 7.4 million ha in 2019.Rainfed rice fields are known as the most widely practiced method.However, this method only sometimes correlates linearly with increased rice yields.In previous studies in Indonesia, rainfed rice fields reduce by 28% yield compared to water-efficient irrigated rice fields with Intensification System.Some farmers combine rice cultivation with fish farming to implement effective water use.This method is known as mina-padi [2].This agriculture has been known for a long time and provides both carbohydrates and proteins.This agriculture also provides many socio-economic benefits.
Thus, Minapadi increases the availability of nutrients for rice plants and increases the content of organic matter originating from the decomposition of feed residues and weeds, which are financially beneficial for farmers with low inputs and promotes environmental friendliness; the main objective of Minapadi farming system is to increase the productivity of paddy fields, implementing sustainable cultivation and creating a sustainable ecosystem [3].Minapadi uses fish waste as nutritional fertilizer, However, Rice-fish cultivation is essential in Indonesia.However, its potential is underestimated, where the Minapadi system is only 142,122 hectares or only about 1 percent of the total rice land area.[24], described that Even though the Mina Padi system is an effective way to increase welfare and realize food sovereignty, there are many good reasons to support this target concept, as it can provide more food sources, make better use of scarce resources, protect the environment, and create opportunities for added value.

Materials and method
This section describes the research location, preparation, implementation, and Observation parameters.Furthermore, one of the formulations would be a recommendation.

Study area
This research was carried out in Laiya village, Cenrana sub-district, Maros Regency, South Sulawesi, when the research was carried out from October 2022 to January 2023.

Research preparation
The research map is made with a size of 5 x 6 m 2 , where each experimental plot was made a circular model trench with a width of 40 cm and a depth of 50 cm.The types of fish used in this study are Tilapia fish with an average weight of 8-10 grams, recommendations from Susanto, 1996, and confirmed in research by Ketut, 2020.It states that the population of fish weighing 8-10 grams is 10 thousand -12 thousand per hectare, or one head per meter.So, for plots with an area of 30 m2, the fish population is 30 individuals per plot.
The rice used in this study was the Inpari variety, with a harvest age of approximately three months.The feed used in this study was made in the nutrition laboratory and fishery feed, where there were four different nitrogen levels: control, 5%, 7%, and 9%.

Research implementation
This land preparation includes plowing and block-making to avoid contamination or mixing of water from each plot.Rice seed planting is carried out after land preparation.The seeds used are seeds that have the same height using the 3:1 row legowo planting method, where every two rows of plants have a 40 cm wide aisle, the distance between the rows is 20 cm while the distance in the rows is closer, namely 10 cm. 1 planting hole planted 3-4 rice seeds.Fish seeds were stocked seven days after rice planting.
Feeding the fish is done three times a day by spreading it on the empty parts in the Hajar legowo cropping system to ensure the fish consume all the feed; then, the feeding is done using a satiation system.Paddy maintenance activities include managing stagnant water in plots while weeds at a reasonable level are left as fish feed, especially controls.Pest and disease control is done by applying vegetable pesticides and fish maintenance as feeding satiation.

Observation parameters
The flow of nutrients can be seen from changes in nutrient content that occur in the field with analyses carried out before cultivation, the transition from the vegetative to the generative phase.The feed will be tested in the laboratory to ensure that the nitrogen content is in accordance with the treatment to be carried out in the field, namely 5%, 7%, and 9%.Feces from fish will be taken from the aquarium in the laboratory with the assumption that it is similar to fish in the field due to the same treatment in feeding, both in the form of frequency, dosage, and timing of feeding.The nutrients from the feces that will be tested are the nitrogen content.
The soil was taken using random sampling for each treatment and replicates; for N nutrients, samples were taken at three different phases, namely before planting, the transition from the vegetative to generative phase, and before harvesting, to see changes in nutrient elements from interactions that occur in the field, while For pH, CEC, BO, and texture samples taken before cultivation was carried out, the samples were analyzed at the Chemistry and Soil Fertility Laboratory of the Faculty of Agriculture, Hasanuddin University.Fish were taken based on the average weight of the harvested fish, then the protein content of the fish samples was analyzed to see the effect of nitrogen feed on protein levels in the fish harvested.
The water quality in each research location map can be seen by measuring several parameters in the field: dissolved oxygen (ppm) or dissolved oxygen (DO), pH, and temperature.

Feed quality
The feed given in the study was proven at the Pokphand Laboratory, showing that different nitrogen treatments were appropriate, namely 5%, 7%, and 9% (Table 1).The composition of the feed given was obtained from organic ingredients in the form of fish meal, shrimp meal, Indigofera flour, corn flour, fine bran, starch, fixed minerals, and fish vitamins.Differences in nitrogen content show a significant effect on the performance of rice plants and tilapia; apart from that, feed serves as a substitute for fertilizer for plants, good protein is also needed by tilapia, while rice plants provide shade and alternative feed for tilapia.Although the best protein quality reaches the vegetative phase, it is optimal at 7% Nitrogen or around 40% protein, 10% greater than the existing recommendations.The use of feed with very high nitrogen levels did not significantly affect the growth performance of tilapia plants and fish.

Water quality
The water in the research location was tested using a TDS meter, showing temperature, DO, and pH.(Table 2).The results of the TDS meter show that the average temperature of the study location ranged from 27 to 28 degrees Celsius.The temperature was suitable for the growth of tilapia, while dissolved oxygen showed that plots with high nitrogen content tended to be lower than plots.The feed treatment with lower nitrogen content, although the treatment without feed obtained an average higher oxygen content.Meanwhile, the pH of the water was not significantly different, namely in the range of pH 10.Overall, the water quality is suitable for Minapadi cultivation.

Growth performance of rice plants
Rice plant performance is seen by measuring the lowest, medium, and highest plants (Table 3).The average plant height is obtained in each treatment, the measurement is carried out at the peak of the vegetative phase of the plant, and the results are obtained that the treatment with the highest nitrogen feeding gives the best results on growth performance; this because tilapia fish do not fully consume feed given on the plots, some is soluble in water, sedimented in the soil, and used by plants as a substitute for fertilizer to support the growth of rice plants.

Tilapia growth performance
The performance of tilapia was seen by weighing the fish's weight and measuring the fish's length and width (Table 4).
Fish weight (grams) H+38 The average weight and size of the fish in each treatment were obtained and weighing and measurement were carried out when the fish entered the second month after being unloaded.The results obtained were that treatment with different nitrogen feeds, on average, resulted in weight and size that were not significantly different.In contrast, plots that were not given feed resulted in lighter and smaller tilapia weight and size.Up to three times with plots given feed treatment.

Faecal Nutrition of Tilapia
Tilapia feces were examined by testing the crude protein content in the feed chemistry laboratory, Department of Animal Husbandry (Table 5).The analysis was carried out by taking the feces from each treatment when the fish entered the second month, and the result was that the treatment with 7 percent nitrogen feed had the highest crude protein content compared to other treatments; this indicated that 40 percent more protein feed was consumed by fish than other treatments.

Conclusion
Based on the results obtained from the research, it can be that treatment with 9 percent nitrogen content obtained the best results for rice plant growth performance.Furthermore, treatment with a nitrogen content of 7 percent obtained the best results for tilapia growth performance.However, treatment without providing feed had a significant effect on the growth performance of tilapia but was not significantly different from the growth performance of rice plants.
and fish can also eat existing weeds and pests, reducing pesticide use.Minapadi cultivation generally considers local wisdom in certain areas.