Service Crops and Management
In the 30th Aapresid Congress, the Aapresid Service Crops Network, with the support of Gervasio Piñeiro, spread knowledge of drying dates and selection of species so that they could be added and all makes sense.
Wednesday 10 August
Agroecosystem functioning is linked to carbon (C) and nitrogen (N) dynamics, which will be influenced by tillage and crops included in rotations. In general, variables sensitive to the inclusion of different rotations are related to newer fractions of C and N. Long-term trials provide a favorable experimental framework for assessing soil health.
For this reason, the Service Crops Network, a collaborative project of Sistema Chacras Program of Aapresid, has been bringing together producers, reference individuals and science for 6 years to find answers that facilitate the adoption of this technology. The Technical Coordinator of the SCN, Gervasio Piñeiro (FAUBA-CONICET), showed the results of the latest studies that dispelled the fears that threaten the inclusion of these crops: water consumption and nutrient immobilization.
In order to assess the effect of different termination dates on biomass production and water collection, early and late drying was examined on CS planted on May 1 across 14 sites from Tucumán to Tandil. As expected, the late date (November 7) generated more biomass compared to the early drying on October 3.
However, in the early dries, the following wider window (70 days) until the summer crop allowed the recovery of more water than the late date which, although it accumulated more biomass, only had one month of recharge. Notably, this pattern was not as clear at the northern sites, "where having CS more time in the lot was to the detriment of living biomass." Therefore, "this year we would have to give them more time in the south, while in the north we could be drying earlier, aiming to save water," he advised.
Regarding this last point, Piñeiro emphasized that in general the two drying dates ended with a similar amount of water as the 224-day chemical fallow. While in most cases "short-term fallows" of 40 days allowed adequate water recovery in the profile, the 70- to 80-day window ensured the recharge of all the sites. "The range between 40 and 80 days is what we have to start adjusting for each zone, year, and lot," he added.
Another purpose of the SCN was to assess the inclusion of long-cycle Italian rye grass, in order to generate good biomass with a lower C:N ratio than other gramineae. The results showed that although this species produced 2,000 kg less, both in early and late dates (2,500 kg and 3,700 kg, respectively); it enhanced quality, because it was in vegetative stage. Consequently, according to the specialist, it is emerging as an interesting CS for very long window that lead to decompose its stubble at lower temperatures.
Regarding the mixture of different proportions of gramineae and legumes, it was found that the 50:50 ratio produced more than the average of pure crops, and it was produced even more on late dates (37%.) Apart from this, its quality is optimal for feeding the soil and promoting the rapid availability of nutrients. In case a crucifer is added to the mixture, a better behavior was observed at early dates, since their productivity quickly increases and therefore it becomes more competitive than weeds. If we talk about quality, not only is the aerial biomass that matters, but also the root biomass: 1 t of roots is 500 kg of C in the soil and an equivalent amount of exudates, which make a fundamental contribution to the formation of the most stable organic matter in the soil, associated with minerals.
Finally, the specialist emphasized, "The data show that cash crops end up producing more when CSs are included in the rotation, but we must pay attention to water management, nutrient immobilization and temperature of decomposition of biomass."
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