Beat the clock: Speeding up the improvement of manure management at Indonesian smallholder dairy farms

The higher demand for milk has increased the numbers of dairy cattle at Indonesian smallholder dairy farms. Smallholder dairy farms now have, on average, 2 to 4 cattle per farm and the Indonesian government plans to increase this to 7 cattle per farm. The dairy farmers not only produce more milk, 10-14 litres milk per cow per day, but also more manure. Most of these farms are in peri-urban areas with limited land to store and apply manure. As a result, most of the manure is discharged which pollutes the environment. Losses of nutrients from manure, mainly nitrogen (N) and phosphorous (P), contribute to eutrophication of the Citarum river, one of the longest rivers in Indonesia. Nitrate (NO₃^‑) pollution can also cause groundwater to become unsuitable for drinking. During storage, treatment and application of manure, moreover, gases can emit to the environment (i.e., nitrous oxide (N₂O), ammonia (NH₃) and methane (CH₄)). The Indonesian smallholder dairy farmers need to beat the clock and speed up improving their manure management to avoid polluting the environment. However, the knowledge lacks on how large the challenge is and how this can be done.

Improving manure management involves many aspects, including feeding type, quantity, and composition, the physiological stage of the animals, land for storing and applying manure, and costs for manure management.

To speed up the improvement of manure management at Indonesian smallholder dairy farms, this PhD research evaluated emissions to the environment associated with manure management at multiple levels: animal, farm, regional, and value chain. Through this approach, we identified the major causes of emissions related to manure management and to come to integrated potential improvement options.

Animal level

Information about N-P excretion of dairy cattle can be used to estimate nutrient losses from different manure treatment options and to quantify differences in nutrient use efficiency among farms and manure management systems. At animal level, we developed a model to accurately predict losses of N-P. To predict the N excretion in faeces (Q_FN) we used the Lucas equation describing the apparent digestibility of nutrients, independent of the feed, based on true digestibility, and the endogenous loss of that nutrient in the faeces. It is widely used in nutrient digestibility studies for ruminants, mostly for protein and N (1,2). Since most of P ends in faeces, we calculated P excretion based on the difference between phosphorous intake and retention by the animal (3).

Figure 1 shows the model evaluation of Q_FN. Results indicate that the model presented in this study can be applied under very different circumstances. Using the proposed Q_FN model and calculation of P excretion enabled us to predict N-P from manure. The average total N excretion was 197 g animal^-1 day^-1 which consists of faecal N (96 g animal^-1 day^-1) and urinary N (101 g animal^‑1 day^‑1). The average total P excretion was 56 g animal^-1 day^-1. From the results we calculated nutrient use inefficiency which we found to be higher than in other literatures. This high nutrient use inefficiency can be explained by the low nutrient utilization of the cattle due to limitation by other nutrients, by genetic potential, by health-related factors, or it could be that the diets contained too many nutrients (4).

Farm and regional level

Information on N-P excretion at animal level can subsequently be used to estimate the flows and losses of nutrients on dairy farming systems (DFS). Nutrient balances of DFS are determined as the difference between nutrient inflows (feed and artificial fertilizer) and outflows (meat, livestock, and manure). The results are under development, but if we find that the total nutrient inflows into the DFS exceeds the total outflows, we can assume that the difference is lost to the environment in the form of leaching and volatilization N and run-off of P. If the total nutrient inflows into the DFS is lower than the total outflows, we assume nutrient extraction from the soil. Once we know this we can scale up the nutrient losses from the farm level to the regional level to determine the sector’s contribution to the pollution of the Citarum river and the potential options for improvement.

Value chain level

In the dairy value chain manure management contributes to global emissions. Here, we performed a life cycle assessment (LCA) to estimate greenhouse gas emissions intensity (GHGEI) from smallholder dairy farms.

Seasonal differences in management practices, including manure management can be an important source of variability of GHGE estimates of smallholder dairy farms in the tropics. Figure 2 shows the results of our LCA. The GHGEI in the rainy season was on average 1.3 kg CO₂-eq/kg fat-and-protein-corrected milk (FPCM) which was higher than in the dry season (1.0 kg CO₂-eq/kg FPCM). The difference can be explained by emissions from enteric fermentation, manure management and forage cultivation. Emissions related to manure management were generally lower in the dry season than in the rainy season due to different management systems (5).

Potential improvement options

Having evaluated emissions to the environment associated with manure management at multiple levels we identified a number of potential improvement options. The key insight of this research is that manure management improvements should be done simultaneously at animal, farm, regional and value chain level. At animal level, nutrient use inefficiency of dairy cows needs to be reduced. Literature shows that this can be done by providing a balanced feed ration, reducing heat stress of cows, improving animal health, and genetic of animals (6–9). Through our farm visit, we also discovered that at farm and regional level, a step towards improving manure management is to reduce the farms’ nutrient imbalance by increasing manure collection and using manure as fertilizer. We also found that biodigesters were not used optimally, and optimizing the use of bio-digesters could improve manure management at farm level. These strategies are also relevant at the value chain level. Additionally, improving manure management requires a proper enabling environment. In our view, the relevant strategies to setting up an enabling environment are educating farmers, encouraging collaboration between stakeholders (dairy cooperatives, dairy farmers, crop farmers, composters, government etc.), relocating dairy farming, and phasing out subsidies.

In conclusion, the govrnment strategy to meet the higher demand for milk by adding more dairy cattle in the urban area should be approached carefully. This research calls for urgent improvements to manure as current management causes environmental impacts at animal, farm, regional and value chain. Thankfully there are many ways manure can be managed better. Shifting from poor manure management to better manure management will not be feasible without involving many stakeholders which may not be easy and may take time to realize, but this process must start now for a sustainable Indonesian dairy production in the future.

References

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