Improving the estimation of soil water evaporation based on days after wetting

Soil evaporation constitutes a major pathway of water loss in agriculture. Understanding its dynamics in the face of drying and soil cover is fundamental to improve both simulation models and the sustainability of production systems. Thus, the objective of this study was to estimate soil evaporation as a function of drying and percentage of soil cover. Three experiments were carried out in three different periods. In each of the periods, in parallel and in an adjacent area, an experiment was carried out to evaluate the influence of weighing micro-lysimeter (ML) height on the estimation of direct soil evaporation. The experiments were installed with a completely randomized design. For the experiments that measured evaporation as a function of cover, the treatments consisted of six different percentages of cover of the internal area of the ML (0%, 10%, 25%, 50%, 75% and 100%), with four replicates, using artificial plants to cover the soil. The experiments that estimated evaporation as a function of ML height were conducted with eight repetitions and three different ML heights (100, 200 and 300 mm). It was observed that the accumulated evaporation up to 25 days after wetting was 52% and 53% lower in micro-lysimeters with 100 mm height, compared to those with 200 and 300 mm height, respectively, for all experiments. The new model developed to calculate soil evaporation as a function of the days after wetting and percentage of soil cover showed excellent performance (NSE > 0.95).     

Flavonol Polymer Technology for Encapsulation of Liquid Phosphorus Fertilizers for Enabling A Slow-Release Process in Soil to Extend Usability and Reduce Leaching

A proprietary Flavonol Polymer Technology (FPT), designed by AgroLiquid, is an agent for encapsulating different chemistries on the polymer by impregnation to provide extended release of nutrients and optimize yield. Based on FPT, FPT-Product (Pro-Germinator®) a 9-24-3 (% N, % P₂O₅, and % K₂O w/w) manufactured to slow the phosphorus release process in soil and extends its usability by the plant. Phosphorus release was evaluated using micro-lysimeters installed in soil and used as a tool for the collection of the plant-usable phosphorus dissolved in the soil solution. A rate of 22 kg of P₂O₅/hectare of liquid formulations was banded in-furrow with four phosphorus liquid fertilizer treatments: (1) orthophosphate (9-18-9), (2) ammonium polyphosphate (10-34-0), (3) FPT-Product (9-24-3), and (4) a control. In-field measurements were collected at 20–60 days after the application for two successive years (2015 and 2016). In both years, averages of measured dissolved phosphorus in the soil solution and exchangeable soil phosphorus at 10-cm soil depth, 20–60 days after planting reported higher values in the FPT-Product treatments while lower values were measured in the other treatments. The results proved that the FPT extended the release mechanism for phosphorus in the FPT-Product at 10 cm depth in the soil, and rendered phosphorus in both the soil and the solution to be used by plants for an extended period after corn planting.     

由双作物系数法确定干旱地区人工牧草基本作物系数地区值的研究

本文采用FAO-56推荐的计算牧草需水量的双作物系数法,应用内蒙古正蓝旗的人工草地试验资料,模拟计算无水分胁迫条件下的人工牧草的需水量(蒸散发)的基础上,分析模拟计算值与Li6400光合作用仪以及微型土壤蒸发器的实测值之间存在的误差,用迭代反推法确定了人工牧草———披碱草生长阶段基本作物系数地区值(Kcb地)为0.203、0.691、0.461。用Kcb地模拟计算了有水分胁迫的披碱草需水量,并用实测值对迭代法确定的Kcb地合理性进行了验证,验证结果表明合理,可用做地区参数来模拟计算人工牧草需水量。     

冬小麦棵间土壤蒸发数值模拟研究

为了探讨作物生长条件下棵间土壤蒸发规律,利用微型蒸渗仪的实测值和土壤潜在蒸发速率对土壤蒸发过程进行了模拟分析,并对Ritchie模型进行了验证。结果表明,返青期土壤蒸发第2阶段的蒸发速率受气象条件的影响较拔节期和灌浆期大。第2阶段土壤累积蒸发量与时间的平方根成正比,其斜率值α不仅仅与土壤的水力特性有关,可能还与气象条件、土壤含水率、作物地表覆盖程度等有关。返青期、拔节期、灌浆期α值分别取为2.5026、2.0477、3.425。Ritchie土壤蒸发模型的模拟值与实测值的均方根误差为0.21 mm/d,平均绝对误差为0.16mm/d,模拟精度较高。     

夏玉米棵间土面蒸发与蒸发蒸腾比例研究

利用连续4年的大型称重式蒸渗仪和小型棵间蒸发器的测定资料，研究了不同灌溉定额条件下夏玉米生长期间的逐日蒸发蒸腾和棵间蒸发过程。结果表明，夏玉米总的蒸发蒸腾量在年际间变化较大，其中叶面蒸腾总量变化较大，在158.44～233.99 mm；棵间蒸发总量变化较小，在171.43～181.52 mm，棵间蒸发量占蒸发蒸腾量的比例(E/ET)在43.57%～52.52%之间。降水和灌溉以及气象因素对夏玉米生育期棵间蒸发的影响较小，而对叶面蒸腾的影响较大。得出充分灌溉和非充分灌溉条件下，棵间蒸发占蒸发蒸腾的比例与叶面积指数的相关系数分别达到0.85和0.77以上。