Optimizing Water and Nitrogen Strategies to Improve Forage Oat Yield and Quality on the Tibetan Plateau Using APSIM

Abstract

There is a great need for improving oat forage production to increase forage supply and protect grassland ecosystems on the Tibetan Plateau. We conducted two field experiments and modeling work to investigate the responses of oat (Avena sativa L.) forage yield and N uptake to water and N applications, and to optimize the water and N scheduling under rainfed and irrigated conditions. The experiments were conducted in 2017 and 2018 at Jintai farm in the northeast of the Tibetan Plateau. Two N-applying rates of 120 and 60 kg ha−1 were tested in 2017, and four irrigation treatments (no irrigation—NI, irrigated 50 mm at flowering—I1, irrigated 50 mm at tillering and jointing—I2, and irrigated 50 mm at tillering, jointing, and flowering—I3) were applied under every N rate in 2018. The Agricultural Production System Simulator (APSIM) was calibrated and validated for the local oat variety. Under rainfed conditions in both years, oat yields under high and low N were 7.98–8.52 and 5.09–6.53 t ha−1, respectively; the high N rate significantly increased forage yield and N uptake compared to low N conditions by 22.2–67.4% (p < 0.01) and 42.0–162.0% (p < 0.01), respectively. In 2018, irrigation increased oat forage yield by 29.8–96.6% (p < 0.01) and increased N uptake by 19.6–50.5% (p > 0.05); N rates had no significant effect on forage yield (p > 0.05), but significantly increased N uptake by 42.6–64.7% (p < 0.01). I2 was superior to I3 in terms of increasing water use efficiency (WUE) while maintaining high forage yield and N uptake. APSIM-oat was calibrated with data under both rainfed and irrigated conditions and was confirmed to have good accuracy and lower normalized root mean square errors (NRMSEs) for phonology dates, forage yield, soil water storage, and N uptake. Scenario analysis was performed with 30-year historical weather data; five N rates were designed for rainfed conditions, and 25 scenarios comprising five N rates and five irrigation levels were designed for irrigated conditions. Simulations showed that the N rate of 90 kg ha−1 resulted in the best performance for oat under rainfed conditions. Under irrigated conditions, irrigation promoted oat nitrogen uptake. Thus, overall an N rate of 120 kg ha−1 in combination with irrigation of 120 mm applied during the vegetative growth period performed the best. This optimized strategy may provide guidance on water and N management of oat forage production in the Tibetan Plateau and similar alpine regions worldwide. The promoted strategy increases yields while reducing water and nitrogen resource wastes, thus decreasing the environmental pollution from agriculture and responding to the sustainable development of farmland ecosystems.

Germination ecology of Chenopodium album L. and implications for weed management

“…Water availability is required for imbibition and activation of metabolic reactions, which regulate embryo development and seedling growth [ 52 ]. Seeds cannot reach the critical moisture threshold required for imbibition under osmotic stress conditions and thus fail to germinate [ 40 ]. In this respect, reduced germination could serve as a survival strategy for unpredictable and low precipitation conditions, which guarantees seed longevity within seedbank until sufficient moisture is available for seed germination [ 42 ].…”

“…The seeds were placed at the soil surface which obtained the highest germination percentage, and the resultant powder of oat straw was spread on the soil surface at a rate equivalent to the specified levels of the treatments. The amount of oat residue (as straw mulch) used in this study was representative of the quantity of mulch levels after harvest found in irrigated and dry land farming systems in China [ 39 , 40 ]. The trials were incubated under constant temperatures of 25°C and 12 h light/ 12 h dark in the incubator, and generally the plot size was 380 L. Seedling emergence, i.e., when the cotyledon was visible above the soil surface, was counted daily for four weeks or until emergence no longer occurred.…”

Assessing the Effect of Intercropped Leguminous Service Crops on Main Crops and Soil Processes Using Apsim Ng

“…These output variables were chosen as they represent important processes of key ecosystem services and disservices in crop production. We compared point estimates, cumulative values or average flows, but the model could also be used to compare differences in daily flows over years or specific periods, or to calculate N or water use efficiency, as done by Ma et al (2022). APSIM also provides information on different N forms and simulates daily rates of transformation between different N pools, which could be valuable when assessing measures to mitigate different N losses, or management of SCs as green manures.…”

Nutrient utilization of native herbage and oat forage as feed for Tibetan sheep (Ovis aries)

“…In Tibetan Plateau, local communities support sown forage crops such as oat. Recently, oat forage production can be more than 10.7 t of dry matter/ha in the Tibetan plateau (Ma et al, 2022). However, about 70% of artificial pasture in Qinghai–Tibetan Plateau (QTP) is cultivated by oat forage to eliminate the seasonal imbalance between livestock and herbage production (Xu et al, 2017).…”