Optimization of soybean productivity, quality, and profit through soybean-maize-mung bean intercropping in East Java, Indonesia

Background

Soybean is one of the most important agricultural commodities in international trade, and their production is important for Indonesia because people consume soybeans as one of the daily protein sources with the traditional dishes tofu and tempeh. However, soybean national production in Indonesia has been declining and around 95% of soybeans are imported currently. The decline in domestic soybean production and increase in imports is a threat to Indonesian food self-sufficiency.

The soybean importation resulted in Indonesian local soybeans falling in price. Therefore, recently, many farmers on Java Island, which was historically the main region of soybean production in Indonesia, have stopped producing soybeans and mostly replaced them with maize, which generates a larger margin than soybean.

To address the problem of Indonesian soybean production, expanding more planting areas might not be a feasible option in Java island, which has the largest population density with high land demand in Indonesia. Growing more soybean requires replacing other crop species. Hence further research is needed to design cultivation systems that can utilize farmland more efficiently while enhancing Indonesian soybean self-sufficiency.

One of the solutions could be to replace the current maize production with soybean-maize intercropping. Nevertheless, usually, soybean yield is less than half of the sole crop yield in soybean-maize intercropping due to the shading by maize. Moreover, the nutritional value of intercropped soybean may be compromised.

One of the possible solutions to the shading problem is to increase the row distance between the taller maize and the shorter soybean by decreasing the row distance between maize rows but increasing the row distance between maize and soybean while maintaining the total width of the strips. The effects of row arrangement in intercropping have not been fully investigated in East Java or anywhere at similar latitudes as in Indonesia.

Moreover, there is little research that adds third crops to maize-soybean intercropping. If shading by the taller maize is the major factor leading to declining soybean yields, and a large gap width between the species is needed to improve soybean production, how about adding a third crop in the available space? Could this increase total system productivity without affecting soybean output?

We use mung bean, which has a similar height to soybeans and has a slightly shorter growing cycle, as the candidate for the third crop as it would not interfere much with soybean growth but provide additional income to farmers.

Project description

This research involves four field experiments, which are two times field experiments per year (Season 1: February-June, Season 2: June-October) for two years in 2022 and 2023. The experiments are conducted at a research field of the Indonesian legume and tuber crops research institute, Ministry of Agriculture, which is located at Probolinggo Regency, East Java province, Republic of Indonesia.

Treatments we test are sole crops (sole maize, sole soybean with two varieties, and sole mung bean) and four intercrops;

1. Replacement intercrop of soybean and maize 2. Replacement intercrop of soybean and maize with wider gap width between soybean and maize 3. Replacement intercrop that adds a mung bean row between soybean and maize in the treatment 2. 4. Replacement intercrop that adds a soybean row between soybean and maize in treatment 2. (In 2022, we tested only one soybean cultivar and did not include intercrop 4).

We conduct intermediate harvests to measure above-ground biomass and leaf area index (LAI), light interception, and radiation use efficiency (RUE). At maturity, we conduct the final harvest. Biomass and grain yield are measured and the land equivalent ratio (LER) is calculated.

Moreover, we measure the nutritional values of all samples of soybeans, maize, and mung beans. Sensory evaluation is also conducted on soybean samples. In addition, we conduct an economic survey and calculate the estimated income from soybean-maize-mung bean intercropping.

A combination of productivity, product quality, and farmer income, will help to understand system functioning more deeply and will clarify to which extent intercropping can help overcome current constraints on soybean production in Indonesia, and which intercropping designs are most promising.

The main chapters of the PhD thesis are as follows.

1. Yield, yield components, land equivalent ratio, and income of different intercropping systems using soybean, maize, and mung bean in East Java, Indonesia 2. Light interception and radiation use efficiency in different intercropping systems using soybean, maize, and mung bean in East Java, Indonesia 3. The difference in nutrient components of different intercropping systems using soybean, maize, and mung bean in East Java, Indonesia 4. (The final chapter is still concealed due to a patent matter of the company)