Uncertainty assessment of soya bean yield gaps using DSSAT‐CSM‐CROPGRO‐Soybean calibrated by cultivar maturity groups

Soya bean yield gap can be caused by different factors resulting in uncertainties when the objective is to use such information for farm decision‐making and reference yield determination. Thus, this study aimed to quantify the soya bean yield gap for four sites, located in Southern and Midwestern Brazil, as well as the uncertainties of that related to cultivars, sowing dates, soil types and reference yields. The crop simulation model DSSAT‐CSM‐CROPGRO‐Soybean was calibrated for cultivars with similar maturity groups, based on the data obtained from the best farmers at the county level. The yield gap by water deficit (YG_WD) was obtained through the difference between potential and attainable yields, and that one caused by sub‐optimum crop management (YG_CM) by subtracting actual yield of each county, obtained from official statistics between 1989/90 and 2014/15 growing seasons, from the estimated attainable yield. The yield was simulated using four sowing dates, three soil types and two soya bean maturity groups by county. The reference yield uncertainty was quantified using yield reference from crop model and regional winners of the soya bean yield context, conducted by CESB (Brazilian Soybean Strategic Committee), for the growing seasons from 2013/14 to 2015/16. The crop model showed a good agreement between measured and simulated crop development and growth using calibration by maturity group, with low root mean square error (347 kg/ha). Southern sites had a mean YG_WD of 1,047 kg/ha, while in the Midwest, it was lower than 100 kg/ha. The YG_CM was 1,067, 528, 984 and 848 kg/ha, respectively, for Castro, PR, Mamborê, PR, Montividiu, GO and Primavera do Leste, MT, representing the opportunity for yield gain when having the best farmers as reference. The maturity groups, sowing dates and soil types showed to be an important source of uncertainty for yield gap determination, being recommended to investigate the farms in detail for an appropriate quantification. The reference yield showed expressive uncertainties, with some farmers presenting conditions to increase their soya bean yields by more than 3,000 kg/ha, when considering as reference the yields obtained by the winners’ farmers. These results show that uncertainties must be reduced when assessing farm yield gaps, in order to ensure that expected rate of soya bean yield growth could be reached by adopting the same technologies from CESB winners and best farmers in the county as a reference.     

吉林省西部地区滴灌条件下宜机械粒收玉米品种筛选

确定宜机械粒收的玉米品种是构建吉林省西部旱作补灌区玉米丰产增效技术模式的重要内容之一。2018年和2019年在吉林省西部地区开展滴灌条件下宜机械粒收玉米品种的筛选试验,测定38个玉米品种的收获子粒含水率和产量,并按玉米子粒含水率和产量水平采用双向平均法作图进行品种分类。结果表明,本研究初步筛选出5个滴灌条件下宜机械粒收玉米品种,分别是迪卡159、福莱77,稷秾108、吉农大889和优迪919。根据品种综合性状分析,吉农大889较优,其次为迪卡159,可以作为适宜吉林省西部滴灌条件下丰产高效栽培的推荐品种。     

河西荒漠灌区紫花苜蓿施肥效应及其基于数据包络分析法的经济效益研究

为科学准确地评判河西走廊苜蓿主产区紫花苜蓿饲草生产中施肥措施对其产品质量及生产收益的影响,本研究以“甘农3号”紫花苜蓿为材料,通过2016、2017年2年田间试验,以该区域紫花苜蓿饲草生产的平衡施肥推荐方案(N 103.5 kg·hm^-2、P₂O₅ 105 kg·hm^-2、K₂O 90 kg·hm^-2)为对照,探讨了不施肥及3种不完全施肥(缺氮偏施、缺磷偏施、缺钾偏施)处理下紫花苜蓿的生产性能,并采用数据包络分析法(DEA)对其经济效益进行分析。结果表明:与不施肥相比,施肥措施各处理均显著提高紫花苜蓿产量、蛋白总量,降低其酸性洗涤纤维和中性洗涤纤维,提高了相对饲用价值,从而改善了紫花苜蓿品质,并有效增加了经济效益;与氮、磷、钾平衡施肥相比,各偏肥处理的紫花苜蓿产量和品质均显著低于平衡施肥,尤以缺磷偏施的降幅最大,2016、2017年2年的产量和蛋白总量降幅分别达到25.9%、25.7%和33.4%、33.1%。因此,磷是河西荒漠灌区紫花苜蓿饲草生产的养分限制因子,氮、磷、钾对该地区紫花苜蓿生产性能影响顺序为:磷>氮>钾。运用数据包络分析法(DEA)分析出河西荒漠灌区紫花苜蓿的施肥效应为氮、磷、钾平衡施肥的经济效益最优,为DEA有效;不完全施肥的3个评价单元及不施肥评价单元为DEA无效,其中,不施肥经济效益最低,3个不完全施肥评价单元中的缺磷偏肥的紫花苜蓿经济效益比缺氮偏肥和缺钾偏肥更低;另外还以DEA模型推算出不同施肥措施下紫花苜蓿饲草生产经济效益改进的具体方案,其中,不施肥的紫花苜蓿饲草生产需调整的幅度最大,调整额度达10678.88 CNY·hm^-2,各施肥措施需调整的幅度排序为:不施肥>缺磷偏施>缺氮偏施>缺钾偏施。     

基于GIS和迈阿密模型的全球灌溉需水量计算

通过计算光温生产潜力、气候生产潜力、光温潜力需水量、灌溉需水量以及衍生的可持续垦殖率指标，以解决农业生产潜力、农田熟制、灌溉定额、宜农荒地垦殖适宜性评价等农业发展问题。以迈阿密模型为理论基础，利用GIS空间分析的研究方法，计算出了上述指标的高精度全球分布场，得出全球光温生产潜力为2 260×10⁸ t干物质，气候生产潜力为1 253×10⁸ t干物质，灌溉需水量总计为12 441 km³。主要结论有：热带雨林区除外，全球气候生产潜力高值区同当前农业区高度吻合，表明农田气候潜力已经被人类充分利用；在温带地区，可持续覆膜雨养垦殖率＞2/3的地区适宜开垦宜农荒地，发展雨养农业。根据迈阿密模型计算得出的灌溉需水量可作为制定农田喷灌定额的重要依据；覆膜滴灌节水效果最佳，可持续覆膜滴灌垦殖率为各种垦殖率中最大值，可作为指导宜农荒地资源开发和多熟制农业发展的主要指标。     

基于AquaCrop模型的夏玉米生长模拟及灌溉制度优化

为评价AquaCrop模型在关中地区的适用性并寻求最佳的灌溉制度，对夏玉米在不同灌溉与施氮水平下的生长进行模拟和验证，并利用校验后的模型研究了3种不同降雨年型以及11种灌溉模式下夏玉米产量和水分利用效率的变化特征。结果表明：AquaCrop模型可以较好地模拟关中地区不同灌溉与施氮水平下夏玉米产量和生物量，模型模拟的产量与实测值之间的决定系数（R²）、均方根误差（RMSE）、标准均方根误差（NRMSE）、符合度指数（d）和纳什效率系数（E_NS）分别为0.919、0.249 t·hm^-2、4.112、0.977和0.915；对于地上部生物量，模拟值与实测值的R²、RMSE、NRMSE、d和E_NS分别为0.860、0.977 t·hm^-2、6.407、0.933和0.694。利用校验后的模型分析了试验区内3种不同降水年型条件下11种灌溉模式的夏玉米产量和水分利用效率的变化特征，依据模拟结果及夏玉米生理需水规律，同时为了实现高产和高水分利用效率，得出不同年型的优化灌溉制度为：若能保证出苗整齐，湿润年可不灌水，此时也能获得较高产量和水分利用效率；平水年推荐在拔节期灌水60 mm，能节约50%水资源，亦能保证稳产；干旱年推荐在拔节期和抽雄期各灌水60 mm，可获得高产和高水分利用效率。     

控灌改良对黄河三角洲盐碱地玉米生长与产量的影响研究

本文以黄河三角洲盐碱地玉米为研究对象,利用黄河泥沙对盐碱地进行改良试验,分析不同黄河泥沙施用量和不同灌水量水平对玉米株高、叶面积、干物质量和产量的影响,探讨适宜的泥沙施用量和灌水量。结果表明：玉米的生长和产量都随着泥沙施用量和灌水量的增加而增大,泥沙施用量均大于灌水量对其的影响。株高、叶面积指数、干物质量产量均在在泥沙施用量为6cm,灌水量为150mm处理最大,干物质积累量在成熟期最大为20460kg/hm_²；夏玉米产量最大为11220kg/hm_²。     

芝麻不同生育阶段需水特性与干旱灌溉应用研究

探讨芝麻不同生育阶段需水特性与干旱灌溉水分生产效率,为芝麻高产栽培的合理灌溉和水分管理提供科学依据,2013-2018年在安徽、新疆等不同地域,选用6个芝麻主栽品种,开展芝麻不同生育阶段需水特性和灌溉水利用研究。结果表明：盆栽芝麻的全生育期蒸腾需水量平均为283.59mm,品种间差异大,形成100kg芝麻籽粒蒸腾需水量为263.56mm(175.7t/666.7m²),苗期、蕾期、初花期、盛花期、终花期、成熟期的蒸腾需水量分别为18.76mm、21.91mm、21.03mm、149.28mm、71.21mm和34.79mm,蒸腾模系数为5.89%、7.21%、6.85%、47.07%、23.93%和9.05%；盛花期最大,出苗期最小。池栽芝麻全生育期需水量531.36mm,其中株间蒸发量、蒸腾量分别占全生育期需水量的46.1%和53.9%；株间蒸发量最大的时期为苗期；蒸腾量最大的时期为花期。芝麻苗期、花期和成熟期需水模系数平均为18.65%、66.79%和14.56%。合肥基地出苗期、临泉基地花期遇旱喷灌,水分生产效率高达0.61kg/m³和0.65kg/m³；新疆精河基地按需滴灌处理比传统滴灌方式的水分生产效率提高43.28%,节水19.61%,这对水资源匮乏的新疆干旱区来说意义重大。芝麻需水量与栽培条件、品种、气温(r＝0.99)等密切相关。在芝麻不同生育阶段遇旱灌溉是提高水分生产效率和产量的关键措施之一。     

江西省水稻蓄雨间歇灌溉模式初探

【目的】探索水稻蓄雨间歇灌溉模式节水减排效益。【方法】以鄱阳湖区双季早晚稻为试验材料,采用大田和测坑试验,研究了水稻蓄雨间歇灌溉模式对灌溉定额、排水定额、降雨有效利用率、产量、稻田水分生产率,以及氮、磷排放量的影响,并与间歇灌溉和常规淹水灌溉试验进行了分析比较。【结果】与淹水灌溉、间歇灌溉相比,蓄雨间歇灌溉灌排水量、灌排次数明显减少。双季早晚稻年平均灌水量分别减少975m^3/hm^2和1251m^3/hm^2,年平均灌水次数分别减少8次和7.5次;年平均排水量分别减少729 m^3/hm^2和893 m^3/hm^2,年平均排水次数分别减少5.8次和3.1次;蓄雨间歇灌溉降雨有效利用率明显提高。早稻降雨利用率分别提高12.40%和9.14%,晚稻分别提高6.84%和6.42%;蓄雨间歇灌溉模式下,双季早晚稻总氮排放量年平均减排7.64 kg/hm^2和3.12 kg/hm^2,减排幅度34.93%和14.26%;双季早晚稻总磷排放量0.180kg/hm^2和0.095kg/hm^2,减排幅度37.25%和70.59%。【结论】蓄雨间歇灌溉模式具有明显的节水、减排和提高降雨有效利用率的效果,在我国南方多雨地区具有较强的推广应用空间。     

痕量灌溉对棉花花铃期光合性能日变化及产量的影响

【目的】明确痕量灌溉方式在干旱区灌溉棉田的适用性。【方法】本研究以中棉所92为供试材料,系统监测了痕量灌溉不同埋管深度30 cm(D30)、40 cm(D40)和50 cm(D50)和膜下滴灌(CK)4个处理的棉花花铃期光合日变化及产量效应。【结果】①不同处理下净光合速率和气孔导度的日变化均呈双峰曲线变化趋势,且D30处理各时段的净光合速率和气孔导度均高于其他处理。②不同处理下的胞间CO2摩尔分数日变化均呈广口"V"字形双峰曲线变化趋势,蒸腾速率日变化均呈单峰曲线变化趋势,最大值出现在14:00h。③D30处理的2年平均籽棉产量和平均皮棉产量最高,分别为5 734.28和2 454.53 kg/hm^2,其中籽棉产量分别比CK、D40和D50处理高出1.09%、7.63%和11.38%,皮棉产量分别比CK、D40和D50处理高出3.49%、8.32%和1.61%。【结论】综合光合性能日变化和产量分析得出,内蒙古阿拉善地区采用埋管深度为30 cm的痕量灌溉技术为最佳。     

Low soil temperature reducing the yield of drip irrigated rice in arid area by influencing anther development and pollination

Drip irrigation can produce high rice yields with significant water savings; therefore, it is widely used in arid area water-scarce northern China. However, high-frequency irrigation of drip irrigation with low temperature well water leads to low root zone temperature and significantly reduce the rice yield compared to normal temperature water irrigated rice, for example, reservoir water. The main purpose of this paper is to investigate the effects of low soil temperature on the yield reduction of drip irrigated rice in the spike differentiation stage. The experiment set the soil temperatures at 18°C, 24°C and 30°C under two irrigation methods(flood and drip irrigation), respectively. The results showed that, at the 30°C soil temperature, drip irrigation increased total root length by 53% but reduced root water conductivity by 9% compared with flood irrigation. Drip irrigation also increased leaf abscisic acid and proline concentrations by 13% and 5%, respectively. These results indicated that drip irrigated rice was under mild water stress. In the 18°C soil temperature, drip irrigation reduced hydraulic conductivity by 58%, leaf water potential by 40% and leaf net photosynthesis by 25% compared with flood irrigation. The starch concentration in male gametes was also 30% less in the drip irrigation treatment than in the flood irrigation treatment at soil temperature 18°C. Therefore, the main reason for the yield reduction of drip irrigated rice was that the low temperature aggravates the physiological drought of rice and leads to the decrease of starch content in male gametes and low pollination fertilization rate. Low temperature aggravates physiological water deficit in drip irrigated rice and leads to lower starch content in male gametes and low pollination fertilization rate, which is the main reason for the reduced yield of drip irrigated rice. Overall, the results indicated that the low soil temperatures aggravated the water stress that rice was under in the drip irrigated environment, causing declines both in the starch content of male gametes and in pollination rate. Low temperature will ultimately affect the rice yield under drip irrigation.