Adaptive management of crop growing periods by adjusting sowing dates and cultivars is one of the central aspects of crop production systems, tightly connected to local climate. However, it is so far underrepresented in crop-model based assessments of yields under climate change. In this study, we integrate models of farmers’ decision making with biophysical crop modeling at the global scale to simulate crop calendars adaptation and its effect on crop yields of maize, rice, sorghum, soybean and wheat. We simulate crop growing periods and yields (1986-2099) under counterfactual management scenarios assuming no adaptation, timely adaptation or delayed adaptation of sowing dates and cultivars. We then compare the counterfactual growing periods and corresponding yields at the end of the century (2080-2099). We find that (i) with adaptation, temperature-driven sowing dates (typical at latitudes >30°N-S) will have larger shifts than precipitation-driven sowing dates (at latitudes <30°N-S); (ii) later-maturing cultivars will be needed, particularly at higher latitudes; (iii) timely adaptation of growing periods would increase actual crop yields by ~12%, reducing climate change negative impacts and enhancing the positive CO2 fertilization effect. Despite remaining uncertainties, crop growing periods adaptation require consideration in climate change impact assessments.

Most rice farmers in Nepal's Terai region do not fully utilize irrigation during breaks in monsoon rainfall. This leads to yield losses despite abundant groundwater resources and ongoing expansion of diesel pumps and tubewell infrastructure. We investigate this puzzle by characterizing delay factors governing tubewell irrigation across wealth and precipitation gradients. After the decision to irrigate, different factors delay irrigation by roughly one week. While more sustainable and inexpensive energy for pumping may eventually catalyze transformative change, we identify near-term interventions that may increase rice farmers' resilience to water stress in smallholder-dominated farming communities based on prevailing types of irrigation infrastructure.

Timely crop planting is a foundation for climate-resilient rice-wheat systems of the Eastern Gangetic Plains—a global food insecurity and poverty hotspot. We hypothesize that the capacity of individual farmers to plant on time varies considerably, shaped by multifaceted enabling factors and constraints that are poorly understood. To address this knowledge gap, two complementary datasets were used to characterize drivers and decision processes that govern the timing of rice planting in this region. The first dataset was a large agricultural management survey (rice-wheat: n = 15,245; of which rice: n = 7597) from a broad geographic region that was analyzed by machine learning methods. The second dataset was a discussion-based survey (n = 112) from a more limited geography that we analyzed with graph theory tools to elicit nuanced information on planting decisions. By combining insights from these methods, we show for the first time that differences in rice planting times are primarily shaped by ecosystem and climate factors while social factors play a prominent secondary role. Monsoon onset, surface and groundwater availability, and land type determine village-scale mean planting times whereas, for resource-constrained farmers who tend to plant later ceteris paribus, planting is further influenced by access to farm machinery, seed, fertilizer, and labor. Also, a critical threshold for economically efficient pumping appears at a groundwater depth of around 4.5 m; below this depth, farmers do not irrigate and delay planting. Without collective action to spread risk through synchronous timely planting, ecosystem factors such as threats posed by pests and wild animals may further deter early planting by individual farmers. Accordingly, we propose a three-pronged strategy that combines targeted strengthening of agricultural input chains, agroadvisory development, and coordinated rice planting and wildlife conservation to support climate-resilient agricultural development in the Eastern Gangetic Plains.

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&lt;p&gt;In many parts of South Asia, electricity for groundwater pumping has been directly or indirectly subsidised by governments to support intensification of agriculture. In contrast, farmers in large portions of the Eastern Indo-Gangetic Plains (EIGP) remain largely dependent on unsubsidised diesel or petrol power for irrigation pumping. Combined with a lack of comprehensive aquifer mapping, high energy costs of pumping limit the ability of farmers to utilise available groundwater resources. This increases exposure to farm production risks, in particular drought and precipitation variability.&lt;/p&gt;&lt;p&gt;To date, research to address these challenges has largely focused on efforts to enhance rural electrification or introduce renewable energy-based pumping systems that remain out of reach of many poor smallholders. However, there has been comparatively little focus on understanding opportunities to improve the cost-effectiveness and performance of the thousands of existing diesel-pump irrigation systems already in use in the EIGP. Here, we present findings from a recent survey of over 432 farmer households in the mid-western Terai region of Nepal &amp;#8211; an important area of diesel-pump irrigation in the EIGP. Our survey provides information about key socio-economic, technological and behavioral aspects of diesel pump irrigation systems currently in operation, along with quantitative evidence about their impacts on agricultural productivity and profitability.&lt;/p&gt;&lt;p&gt;Survey results indicate that groundwater irrigation costs vary significantly between individual farmers. Farmers faced with higher costs of groundwater access irrigate their crops less frequently, which in turn results in lower crop yields and reduced overall farm profitability. Our data indicate that pumpset fuel efficiency may be a key driver of variability in irrigation costs, with large horsepower (&gt;5 HP) Indian-made pumpsets appearing to have significantly higher fuel consumption rates (1.10 litre/hour and $18,000) and investments costs than alternative smaller horsepower (&lt;5 HP) Chinese-made pumpsets (0.76 litre/hr and $30,000). Despite this, the majority of farmers continue to favour Indian pumpsets due to their higher reliability and well-established supply chains. Variability in access costs is also related to differences in capacity of farmers to invest in their own pumping systems. Pumpset rental rates in the region increase irrigation costs by a factor of 3-4 relative to the cost of fuel alone. Furthermore, rental rates typically are structured on a per-hourly basis, further exacerbating access costs for farmers with low yielding wells or whose irrigation management practices are less efficient.&lt;/p&gt;&lt;p&gt;Our findings highlight that opportunities exist to reduce costs of groundwater use in existing diesel irrigation systems through improved access to more energy efficient pumping systems. This would have positive near-term impacts on agricultural productivity and rural livelihoods, in particular helping farmers to more effectively buffer crops against monsoonal variability. Such near-term improvements in diesel pump irrigation systems would also play an important role in supporting agriculture in the EIGP to transition to more sustainable and clean sources of energy for irrigation pumping. However, efforts to enhance irrigation access must also occur alongside improvements to aquifer monitoring and governance of extraction, in order to minimise risks of future depletion such as observed in other parts of the IGP.&lt;/p&gt;

The timing of rice planting has a profound influence on the productivity of the rice-wheat cropping pattern in the Indo-Gangetic Plains (IGP), a system that provides the foundation for food security in South Asia. Nevertheless, strategies for adaptive rice planting in a rapidly changing climate are not well established. In this ex-ante analysis, regional gridded crop model simulations are deployed to investigate the impact of different rice planting strategies on system level productivity, resilience, and environmental benefits. Our results suggest that synchronizing rice planting dates with the monsoon onset substantially outperforms farmer practice (+41%) and static state recommendations in the Eastern IGP. However, planting long-duration rice with the monsoon onset is ineffective in the Northwestern IGP since the later arrival of the monsoon increases the probability of cold damage to rice and terminal heat stress in wheat. Here, fixed planting dates (+12.5%) or planting medium duration varieties at monsoon onset (+18%) performed best. We conclude that resilient and productive rice planting strategies must account for interannual weather variability and divergent climate conditions across sub-regions in the IGP.

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