Sweet corn response to banded phosphorus in the Willamette Valley

Introduction
The previous Oregon State nutrient management guide for sweet corn (Hart et al., 2010) recommended application of banded P fertilizer at planting for fields testing less than 50 mg kg-1 P, using the Bray method. Soil test P is above the 50 mg kg-1 response threshold in most vegetable production fields in the Willamette Valley. At 15 field sites we sampled in 2012-2013, soil test P (0- to 30 cm depth) ranged from 41 to 189 mg kg-1 (median = 127 mg kg-1).
In spite of high soil test P values, many growers routinely apply P in starter fertilizer formulations to sweet corn. The most common starter fertilizer formulations used to supply N (granulated monoammonium phosphate [11-52-0] and liquid ammonium polyphosphate [10-34-0]) also supply P. For example, when 10-34-0 is used to supply N at 34 kg N ha-1, P is applied at 50 kg P ha-1.
Sweet corn varieties grown today are different than those grown when P fertilizer trials with sweet corn were last conducted by Oregon State in the Willamette Valley (McAndrew, 1983). Most current processing corn varieties are higher-yielding and have greater resistance to root rot diseases compared to ‘Golden Jubilee,’ the variety that dominated production prior to 1998.
The objectives of this study were: 1. Evaluate corn ear yield and quality response to starter P fertilizer, using contemporary corn varieties and production practices; 2. Determine whether OSU Extension recommendations for starter P application (Hart et al., 2010) are supported by recent data.
Materials and Methods
In six field experiments, corn was seeded at a target rate of 70,000 seeds/ha with starter P rates of 0, 7, 15, 29, or 59 kg P ha-1. Four trials were conducted in 2012, and two trials were conducted in 2013. Treatment plots were arranged in a randomized complete block design with four replications. In grower fields, each treatment plot was 7.6-9 m wide by 20-23 m long, and plots were positioned within the field so that irrigation was uniform across the plot area. Soil textures at field locations were silt loam or silty clay loam.
All P fertilizer treatments received the same rate of N (28 kg N ha-1 in starter fertilizer plus additional N fertilization per grower practice). Starter fertilizer mixtures were prepared for each treatment using dry granular fertilizers (MAP [11-52-0], urea [46-0-0]), and K Mag [0-0-21-11Mg-21S]. For the zero P treatment, all of the starter N was urea. At the highest rate of P (49 kg ha-1), all of the N was supplied by MAP. A uniform rate of KMag was included in the starter fertilizer for all treatments, supplying 47 kg K ha-1, 28 kg Mg ha-1, and 53 kg S ha-1. The starter fertilizer band was placed 5 cm below and 5 cm beside the seed row, using a hand-push fertilizer spreader.
Results
Corn ear yield did not increase when P fertilizer was applied; ear yields with and without starter P fertilizer were not statistically different at P =0.05 at any of the six field locations. At a single field site with the lowest soil test P (Corvallis 1, 42 mg kg-1 Bray soil test P, seeded May 14, 2013), corn grown without P fertilizer showed visual symptoms of P deficiency at the V6 to V7 growth stage. The P-deficient plants were shorter and had lower biomass, although whole-plant P concentration (3.0 g kg-1 P) was similar to that of P-fertilized plants. At harvest, ear yields at this site were the same for all P fertilizer treatments, including the zero P control.
Results of these trials support a 50 mg kg-1 P sufficiency threshold for soil test P (Bray method; 0-30 cm depth) for modern sweet corn hybrids. See Sullivan et al. (2020) for additional P management recommendations for sweet corn.
This study was funded by the Oregon Processed Vegetable Commission.
References
Hart, J., Sullivan, D., Myers, J., & Peachey, R. 2010. Nutrient management guide for sweet corn: Western Oregon. EM 9010, Corvallis, OR: Oregon State University Extension Service.
McAndrew, D. 1983. Soil fertility investigations on soil solution composition and nutrition of sweet corn and onions. Ph. D. dissertation, Oregon State University, Corvallis.
Sullivan, D.M., Peachey E., Heinrich A. & Brewer L.J. 2020. Nutrient and Soil Health Management for Sweet Corn (Western Oregon). EM 9272. Oregon State University Extension.
https://catalog.extension.oregonstate.edu/em9272

引言
前述俄勒冈州甜玉米养分管理指南（Hart 等人，2010年）建议在种植时对含磷量低于50 mg kg-1的田地施用条施P肥料，采用Bray方法进行测定。威拉米特山谷大多数蔬菜生产田的土壤测试磷含量均超过50 mg kg-1的响应阈值。在2012-2013年间，我们对15个田地进行采样，土壤测试磷含量（0-至30 cm深度）介于41至189 mg kg-1之间（中位数为127 mg kg-1）。
尽管土壤测试磷值较高，但许多种植者仍习惯于在甜玉米的起始肥料配方中施用磷。用于提供氮（颗粒状一铵磷酸盐[11-52-0]和液体磷酸铵[10-34-0]）的最常见起始肥料配方也提供了磷。例如，当使用10-34-0在34 kg N ha-1的氮含量下提供氮时，磷的施用量为50 kg P ha-1。
目前种植的甜玉米品种与俄勒冈州在威拉米特山谷最后进行的甜玉米磷肥试验时种植的品种（McAndrew，1983年）不同。与1998年之前生产中占主导地位的品种“Golden Jubilee”相比，大多数当前的加工玉米品种产量更高，对根腐病的抵抗力也更强。
本研究的目标如下：1. 评估使用当代玉米品种和生产实践，对起始P肥料的甜玉米穗产量和质量响应；2. 确定俄勒冈州大学推广部门对起始P施用建议（Hart 等人，2010年）是否得到近期数据的支持。
材料和方法
在六项田间实验中，以70,000颗种子/ha的目标速率播种玉米，起始P肥料的施用量为0、7、15、29或59 kg P ha-1。其中四个试验于2012年进行，两个试验于2013年进行。处理小区以随机完全区组设计排列，每个小区重复四次。在种植者田地中，每个处理小区的宽度为7.6-9 m，长度为20-23 m，并将小区定位在田地内，以确保在整个小区范围内灌溉均匀。田间地点的土壤质地为壤土或壤质黏土。
所有P肥料处理均接受相同量的氮（起始肥料中28 kg N ha-1加上根据种植者惯例的额外氮肥）。每个处理均使用干颗粒肥料（MAP [11-52-0]，尿素[46-0-0]）和K Mag [0-0-21-11Mg-21S]配制起始肥料混合物。对于零P处理，所有起始N均为尿素。在最高的P施用量（49 kg ha-1）下，所有N均由MAP提供。在所有处理中，均加入均匀的KMag量，提供47 kg K ha-1，28 kg Mg ha-1和53 kg S ha-1。使用手推式肥料撒播器将起始肥料条施于种子行下方5 cm和旁边5 cm处。
结果
施用磷肥料时，甜玉米穗产量没有增加；在六个田间地点中，无论是否施用起始P肥料，在P =0.05的任何情况下，穗产量均无统计学差异。在单一田间地点（科瓦利斯1号，Bray土壤测试磷含量为42 mg kg-1，2013年5月14日播种），在V6至V7生长阶段，未施用磷肥的甜玉米表现出磷缺乏的视觉症状。磷缺乏的植株较矮，生物量较低，尽管整个植株的磷浓度（3.0 g kg-1 P）与施用磷肥的植株相似。在收获时，该地点的所有P肥料处理的穗产量均相同，包括零P对照。
这些试验的结果支持了现代甜玉米杂交种土壤测试磷含量（Bray方法；0-30 cm深度）的50 mg kg-1适宜阈值。有关甜玉米的进一步磷管理建议，请参阅Sullivan等人（2020年）。
本研究由俄勒冈州加工蔬菜委员会资助。
参考文献
Hart, J., Sullivan, D., Myers, J., & Peachey, R. 2010. 甜玉米养分管理指南：西部俄勒冈州。EM 9010，科瓦利斯，OR：俄勒冈州立大学推广服务。
McAndrew, D. 1983. 甜玉米和大葱土壤溶液组成及营养的研究。博士学位论文，俄勒冈州立大学，科瓦利斯。
Sullivan, D.M., Peachey E., Heinrich A. & Brewer L.J. 2020. 甜玉米（西部俄勒冈州）养分和土壤健康管理。EM 9272。俄勒冈州立大学推广。
https://catalog.extension.oregonstate.edu/em9272