Periodic cropping of otherwise permanent pastures can lead to large losses of carbon (C), especially if cropped for maize silage. The long-term effect on C stocks due to periodic cropping depends on whether the lost C is recovered before any future cropping events. Accordingly, this study tested the hypothesis that C lost during periodic cropping would be recovered following a return to permanent pasture within a rotationally grazed New Zealand dairy system. In New Zealand, maize silage is often used as supplemental feed, and its production can be part of the pasture renewal process whereby paddocks are cropped for a year or two before re-establishment of a permanent pasture. The net ecosystem carbon balance (NECB) was measured by combining eddy covariance measurements of the CO₂ exchange (net ecosystem production; NEP) with measurements and estimates of all other flows of C for four years following the re-establishment of permanent pasture in a paddock previously cropped for maize silage. The NECB (negative values indicate C loss from the ecosystem) of the four years was –13, –21, –52 and −242 g C m^-2 for an aggregated total of −328 g C m^-2 indicating further C had been lost. November to January (late spring-summer) was identified as crucial for determining the annual NEP and NECB. NEP during November-January was dependent on climate and farm management. Monthly air temperature negatively correlated with NEP, while rainfall positively correlated with NEP for intervals equivalent to the time between grazing events. Increasing the interval between grazing events to around 28 days during November-January was beneficial for increasing NEP, but longer intervals had limited additional benefit. Small day-to-day management decisions such as the application of effluent, grazing rather than harvesting, and increasing the interval between grazing events have the potential to make small but additive gains to the NECB and provide opportunities to recapture lost C (or minimise further losses) following periodic maize silage cropping of permanent pastures. Data from four years, however, suggests little recovery of previously lost C and indicates that the current return period for periodic maize silage cropping (10–15 years per maize crop) might be too short to maintain C stocks.

定期种植其他永久性牧场会导致碳 (C) 的大量损失，尤其是在种植玉米青贮饲料时。定期种植对碳库的长期影响取决于损失的碳是否在任何未来种植活动之前得到恢复。因此，本研究检验了这样一个假设，即在轮牧的新西兰奶牛系统中，在返回永久性牧场后，周期性种植期间损失的碳将得到恢复。在新西兰，玉米青贮饲料通常用作补充饲料，其生产可以成为牧场更新过程的一部分，即在重建永久性牧场之前，将围场种植一两年。净生态系统碳平衡 (NECB) 是通过结合CO _{2的涡度协方差测量来测量的}交换（净生态系统生产；NEP）与所有其他 C 流量的测量和估计，这些流量是在以前为玉米青贮饲料种植的围场中重建永久性牧场后的四年。四年的 NECB（负值表示生态系统的碳损失）为 –13、–21、–52 和 −242 g C m ^-2，总计为 −328 g C m ^-2表明进一步的 C 已经丢失。11 月至 1 月（春夏末）被确定为确定年度 NEP 和 NECB 的关键时期。11 月至 1 月的 NEP 取决于气候和农场管理。每月气温与 NEP 呈负相关，而降雨量与 NEP 呈正相关，间隔相当于放牧事件之间的时间。在 11 月至 1 月期间将放牧事件之间的间隔时间增加到 28 天左右有利于增加 NEP，但更长的间隔时间带来的额外好处有限。小的日常管理决策，例如污水的应用、放牧而不是收获、和增加放牧事件之间的间隔有可能使 NECB 获得小但累加的收益，并提供机会在永久性牧场定期种植玉米青贮饲料后重新获得损失的 C（或尽量减少进一步损失）。然而，四年的数据表明之前损失的碳几乎没有恢复，并且表明当前周期性玉米青贮饲料种植的恢复期（每株玉米作物 10-15 年）可能太短而无法维持碳储量。