CONTEXT

Climate change affects the timing and length of crop seasons. Adjusting sowing dates is a commonly recommended adaptation, but little is known about its efficacy in practice.

OBJECTIVE

This study investigated farm-level adjustments to sowing and harvesting dates (i.e., the growing period) in response to shifts in meteorological crop seasons during the last 30 years. Impacts on yields and farmers' complementary adaptation strategies were also examined.

METHODS

Using data from 287 farm households in four agroecological zones of the Indus Basin, Pakistan, we explored farmers' perceptions of shifts in seasons and adjustments in crop growing period. We verified these using meteorological station data on temperatures, precipitation and growing degree days.

RESULTS AND CONCLUSIONS

At lower altitudes (irrigated plains and mid-hills), the summer crop season had lengthened and the winter season shortened, but in both seasons the growing period was shorter, due to higher temperatures. The summer growing period was shorter by 5 (±11) days on the irrigated plains, while there was no significant change in length of the summer growing period in the mid-hills. The winter growing period was shorter by 15 (±6) days on both the plains and in the mid-hills, which negatively impacted yields. As an adaptation strategy, changing sowing dates was only somewhat effective in preventing yield losses. Farmers adopted complementary strategies, but these brought additional costs. At higher altitudes (valleys and mountains), the frost period had shortened, resulting in longer summer and winter crop seasons, and longer growing periods. The summer growing period was extended by 7 (±4) days in the valleys and 10 (±6) days in the mountains, while the winter growing period was extended by 3 (±3) days in the valleys and 13 (±5) days in the mountains, positively impacting yields. Farmers' adjustments in sowing dates did not necessarily parallel to seasonal shifts, as farm decision-making also had to consider risks linked to climate variability and management limitations. For the future, farmers at lower altitudes indicated limited further scope for adjusting sowing and harvesting dates.

SIGNIFICANCE

Our results contribute to a contextual understanding of farmers' responses to shifts in crop seasons. They indicate the need for adaptation planning to take advantage of extended growing periods in higher altitude zones, while supporting farmers in areas where seasonal shifts have negative impacts. Our findings furthermore indicate limits to adaptation in regions where agriculture is already challenged and provide suggestions for crop system-specific complementary measures.

中文翻译：

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巴基斯坦不同农业生态区调整生长期的局限性

语境

气候变化影响作物季节的时间和长度。调整播种日期是一种普遍推荐的适应措施，但对其在实践中的功效知之甚少。

客观的

本研究调查了农场层面对播种和收获日期（即生长期）的调整，以响应过去 30 年气象作物季节的变化。还研究了对产量和农民互补适应战略的影响。

方法

我们利用巴基斯坦印度河流域四个农业生态区的 287 个农户的数据，探讨了农民对季节变化和作物生长期调整的看法。我们使用有关温度、降水和生长度日的气象站数据对这些进行了验证。

结果和结论

在低海拔地区（灌溉平原和中山），夏季作物季节延长，冬季缩短，但由于气温较高，两个季节的生长期都较短。灌溉平原夏季生育期短5（±11）天，而中山地区夏季生育期长度无明显变化。平原和中山的冬季生长期缩短了 15 (±6) 天，这对产量产生了负面影响。作为一种适应策略，改变播种日期仅在一定程度上有效防止产量损失。农民采用了互补的策略，但这带来了额外的成本。在海拔较高的地区（山谷和山脉），霜冻期缩短，导致夏季和冬季作物季节更长，生长期也更长。夏季生长期在山谷延长7（±4）天，山区延长10（±6）天，而冬季生长期在山谷延长3（±3）天，13（±5）天在山上的日子，对产量产生积极影响。农民对播种日期的调整不一定与季节性变化平行，因为农场决策还必须考虑与气候变异和管理限制相关的风险。对于未来，低海拔地区的农民表示调整播种和收获日期的空间有限。播种日期的调整不一定与季节性变化平行，因为农场决策还必须考虑与气候变异和管理限制相关的风险。对于未来，低海拔地区的农民表示调整播种和收获日期的空间有限。播种日期的调整不一定与季节性变化平行，因为农场决策还必须考虑与气候变异和管理限制相关的风险。对于未来，低海拔地区的农民表示调整播种和收获日期的空间有限。

意义

我们的结果有助于了解农民对作物季节变化的反应。它们表明需要制定适应计划以利用高海拔地区延长的生长期，同时支持季节性变化具有负面影响的地区的农民。我们的研究结果还表明，在农业已经面临挑战的地区，适应存在局限性，并为针对特定作物系统的补充措施提供建议。