Maize (Zea mays L.) is the essential staple in sub-Saharan Africa (SSA) and Tanzania in particular; the crop accounts for over 30% of the food production, 20% of the agricultural gross domestic product (GDP) and over 75% of the cereal consumption. Maize is grown under a higher risk of failure due to the over-dependence rain-fed farming system resulting in low income and food insecurity among maize-based farmers. However, many practices, including conservation agriculture, soil and water conservation, resilient crop varieties, and soil fertility management, are suggested to increase cereal productivity in Tanzania. Improving planting density, and the use of fertilizers are the immediate options recommended by Tanzania's government. In this paper, we evaluate the economic feasibility of the improved planting density (optimized plant population) and N-fertilizer crop management practices on maize net returns in semi-arid and sub-humid agro-ecological zones in the Wami River sub-Basin, Tanzania. We introduce a bio-economic simulation model using Monte Carlo simulation procedures to evaluate the economic viability of risky crop management practices so that the decision-maker can make better management decisions. The study utilizes maize yield data sets from two biophysical cropping system models, namely the APSIM and DSSAT. A total of 83 plots for the semi-arid and 85 plots for the sub-humid agro-ecological zones consisted of this analysis. The crop management practices under study comprise the application of 40 kg N-fertilizer/ha and plant population of 3.3 plants/m2 . The study finds that the use of improved plant population had the lowest annual net return with fertilizer application fetching the highest return. The two crop models demonstrated a zero probability of negative net returns for farms using fertilizer rates of 40 kg N/ha except for DSSAT, which observed a small probability (0.4%) in the sub-humid area. The optimized plant population presented 16.4% to 26.6% probability of negatives net returns for semi-arid and 14.6% to 30.2% probability of negative net returns for sub-humid zones. The results suggest that the application of fertilizer practices reduces the risks associated with the mean returns, but increasing the plant population has a high probability of economic failure, particularly in the sub-humid zone. Maize sub-sector in Tanzania is projected to continue experiencing a significant decrease in yields and net returns, but there is a high chance that it will be better-off if proper alternatives are employed. Similar studies are needed to explore the potential of interventions highlighted in the ACRP for better decision-making.

中文翻译：

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氮肥和最佳植物种群对坦桑尼亚瓦米河子流域玉米地块盈利能力的影响：一种生物经济模拟方法

玉米 (Zea mays L.) 是撒哈拉以南非洲 (SSA) 和坦桑尼亚的主要主食；农作物产量占粮食产量的 30% 以上，农业国内生产总值 (GDP) 的 20%，谷物消费量的 75% 以上。由于过度依赖雨养农业系统，导致以玉米为基础的农民收入低和粮食不安全，因此玉米种植失败的风险更高。然而，建议采取许多做法，包括保护性农业、水土保持、弹性作物品种和土壤肥力管理，以提高坦桑尼亚的谷物生产力。提高种植密度和使用化肥是坦桑尼亚政府建议的直接选择。在本文中，我们评估了在坦桑尼亚瓦米河流域半干旱和半湿润农业生态区改善种植密度（优化植物种群）和氮肥作物管理实践对玉米净收益的经济可行性。我们引入了使用蒙特卡罗模拟程序的生物经济模拟模型来评估风险作物管理实践的经济可行性，以便决策者能够做出更好的管理决策。该研究利用来自两个生物物理种植系统模型（即 APSIM 和 DSSAT）的玉米产量数据集。该分析共包括 83 个半干旱区和 85 个半湿润农业生态区的样地。所研究的作物管理实践包括施用 40 公斤氮肥/公顷和 3.3 株/平方米的植物种群。研究发现，使用改良植物种群的年净收益最低，施肥的收益最高。两种作物模型表明，使用 40 公斤氮/公顷的肥料施用量的农场出现负净收益的概率为零，但 DSSAT 除外，在亚湿润地区观察到的概率很小 (0.4%)。优化的植物种群在半干旱地区呈现负净收益的概率为 16.4% 至 26.6%，在半湿润地区呈现负净收益的概率为 14.6% 至 30.2%。结果表明，施肥实践降低了与平均回报相关的风险，但增加植物种群经济失败的可能性很高，尤其是在亚湿润地区。坦桑尼亚的玉米子行业预计将继续经历单产和净回报的显着下降，但如果采用适当的替代品，情况很可能会更好。需要类似的研究来探索 ACRP 中强调的干预措施对更好决策的潜力。