# A Survey of Blockchain Applications for Management in Agriculture and Livestock Internet of Things
## 2 Preliminaries
### Blockchain Technology in Agriculture and Animal Husbandry: An Overview
#### 2.2.2 Smart Contracts for Agricultural and Animal Husbandry Automation  
Smart contracts, composed of programmer-written code, establish rules and conditions that automatically execute contract terms once these conditions are met. Operating within the blockchain's decentralized environment, they guarantee execution transparency and immutability. Smart contracts play a crucial role in automating agricultural and livestock processes by executing predefined rules once certain conditions--often captured by IoT devices--are met. For instance, in a dairy farm, a smart contract can automatically settle payments to milk suppliers based on real-time volume measurements collected via sensors, ensuring prompt and accurate compensation without manual intervention. In crop farming, a smart contract might trigger irrigation systems the moment soil moisture levels drop below a predefined threshold, thus optimizing water usage and reducing labor costs. Beyond these fundamental applications, some large-scale operations integrate weather data into their smart contracts to adjust feeding schedules or activate greenhouse controls in anticipation of rainfall or extreme temperatures, effectively protecting both crops and livestock. Similarly, government-led pilot projects have explored smart-contract-based subsidies, where funds are released only after digital monitoring confirms that specific sustainability or productivity benchmarks have been met. By minimizing human errors and administrative delays, these automated processes streamline daily operations and foster trust among farmers, suppliers, and regulators, who can transparently review contract terms and outcomes on the blockchain. As a result, smart contracts serve as a powerful catalyst for data-driven decision-making in modern agriculture and livestock management, paving the way for more resilient and sustainable farming ecosystems. Blocks in a blockchain are essential for securely storing agricultural and livestock-related data in an immutable manner. By linking each block to its predecessor through cryptographic hashes, the blockchain prevents any data within a previous block from being altered without immediately revealing tampering. In a crop supply chain, for instance, each block could record critical information such as harvest dates, storage conditions, transportation logs, and even quality inspection results. If a product is flagged for substandard quality, stakeholders can quickly trace back through the chain of blocks to identify where and when the problem occurred--whether it was in the harvesting process, cold storage, or during transportation. This not only expedites recall procedures when necessary but also helps enforce accountability among different participants in the supply chain. Smart contracts are meticulously crafted programs by software developers tailored to operate on blockchain platforms, exemplified by the use of Ethereum's Solidity language [63]. The consensus algorithm in blockchain networks ensures transactional consensus among all participants, thus maintaining network consistency and security [64]. They incorporate precise operational logic and establish various trigger conditions and  
Figure 4: Blockchain chain-like structure. execution protocols. For instance, a smart contract might stipulate that a financial transfer between accounts only occurs in response to specific events, such as a predetermined date or the reception of particular data. The inherent automation of smart contracts obviates the dependence on conventional intermediaries, like lawyers or banks, substantially reducing transactional time costs and markedly diminishing risks associated with human error or fraudulent activities. Functioning as a decentralized distributed ledger, blockchain allows smart contracts to operate autonomously in a central authority-free environment, executed and verified independently by numerous nodes.