Chiriotti, Pinerolo. (TO) Italy. Cunha, J.P.A.R., L.L. da Silva, W. Boller, and J.F. Rodriguez. 2010. Aplicação aérea e terrestre de fungicida para o controle de doen ...
RESEARCH
Foliar Fungicide Application to Maize: Yield and Grain Hardness Enhancement in Different Environmental Conditions Giulio Testa, Amedeo Reyneri, and Massimo Blandino*
ABSTRACT The dry-milling industry is becoming an interesting distribution channel for maize (Zea mays L.) growers. Since kernels with high hardness are more suitable for the dry-milling process, it is important to investigate new ways of improving for this qualitative parameter. The aim of the research was to evaluate when a fungicide containing a demethylation inhibitor and a quinone outside inhibitor could be effective in controlling fungal disease, increasing grain yield, and improving kernel hardness. A mixture of azoxystrobin and propiconazole was tested at two locations from 2009 to 2012, with two application timings: the beginning of stem elongation and at tassel emergence. The two fungicide timings significantly reduced the incidence of northern corn leaf blight symptoms, a foliar disease caused by Exserohilum turcicum, by, respectively, 30 and 61%. A significant increase of grain yield (between 5 and 7%) and kernel hardness was obtained in both sites by this compound application, mainly when the environmental conditions led to a gradual grain filling. The best result was obtained always for the application at the tassel emergence stage; this treatment could contribute to increased competitiveness in maize production systems, especially for the dry-milling uses.
University of Turin, Dep. of Agricultural, Forest and Food Sciences, Largo Braccini n.2, 10095, Grugliasco (TO), Italy. Received 31 Mar. 2014. Accepted 9 Jan. 2015. *Corresponding author (massimo.blandino @unito.it). Abbreviations: DMI, demethylation inhibitor; FLT, floating test; GDD, growing degree days; GPC, grain protein content; GS, growth stage; NCLB, northern corn leaf blight; QoI, quinone outside inhibitor; TKW, thousand kernel weight; TME, total milling energy; TW, test weight.
M
aize (Zea mays L.) grain hardness is an important feature that plays a key role in the dry-milling process (Shandera et al., 1997). The volume of maize grain directed to dry-milling industries that produce human food and beverages is continuing to increase (Stock et al., 2000) and is becoming more interesting because of its economic value. It is therefore important to provide grain to this particular chain that satisfies its needs. Kernels with high hardness and density, characterized by more vitreous starch, can raise the extraction yield of endosperm particles that are larger than 700 µm, which are commonly known as grits (Wu and Bergquist, 1991). The maize used for the dry-milling industry should be hard, with pericarps and germs that are easy to remove during the process. Softer kernels, with a floury starch, are instead more suitable for the wet-milling process, which is a more versatile, capital-intensive process than the dry-milling one (AMG, 2013). The United States, with its dry-milled maize, focuses primarily on bioethanol production (AMG, 2013), while in Africa and Asia it is used for grits, flour, and meal for the production of flat breads. (Serna-Saldivar et al., 1991). In Europe, several other products are obtained from this processing method:
Published in Crop Sci. 55:1–9 (2015). doi: 10.2135/cropsci2014.03.0262 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. crop science, vol. 55, july– august 2015
www.crops.org 1
flour, cornmeal mush, and grits of different sizes for fermented beer, breakfast products, and cooked or extruded products (Cinquetti, 1987; Blandino et al., 2010). The choice of hybrid is the main parameter correlated to the grit extraction yield. However, it is important to investigate which agronomical practices can positively influence this grain-quality feature and verify their effects in different environmental and agronomic conditions. Crop protection and enhancement products are currently adopted for modern maize production to preserve the yield potential and grain-quality requirements (Diedhiou et al., 2004). The use of foliar fungicides has increased greatly in the United States (Munkvold et al., 2008) and in other countries, such as Brazil (Cunha et al., 2010) and Canada (Hooker et al., 2008), in the last decade. Some of these active ingredients have also recently been allowed in Europe. Foliar fungicides are usually applied to restrain several leaf diseases. Northern corn leaf blight (NCLB) is one of the most common leaf diseases for maize grown in northern Italy. It is caused by Exserohilum turcicum (Bowen and Pedersen, 1988), and it results in elliptical lesions that can generally affect maize leaves after flowering and leads to the premature senescence of crops. Warm and humid weather, late planting, and the presence of previous maize residues can in fact lead to a higher risk of this foliar disease (Bradley et al., 2010). Demethylation inhibitor (DMI) fungicides, especially those belonging to the azole family, are the most efficient in controlling E. turcicum development, both in vitro and in field conditions (Bowen and Pedersen, 1988; Kumar et al., 2009). Quinone outside inhibitor (QoI) foliar fungicides, such as strobilurines, are systemic, and they target the mitochondrial respiration of the fungi. Like DMI fungicides, they can prevent foliar diseases on maize (Bradley et al., 2010), although they are generally less effective for this purpose. However, these kinds of fungicides have been shown to provide physiological benefits to some crops that can result in an enhancement of plant performance and higher yields (Bertelsen et al., 2001; Kato et al., 2011; Nelson and Meinhardt, 2011). It has also been observed that a fungicide application to other crops could delay chlorophyll breakdown and protein degradation, which means delayed senescence (Zhang et al., 2010). On the basis of previous experiments (Blandino et al., 2012), it can be stated that the best application timing for maximizing yield and restraining NCLB leaf symptoms is from the end of stem elongation (growth stage GS 35) (Lancashire et al., 1991; Bleiholder et al., 2001) to flowering (GS 65). However, advantages could also be obtained by spraying at the beginning of stem elongation (GS 30). This treatment timing could be more suitable for farmers, since it can be performed using their own spraying equipment. Although the restraining of foliar diseases and the benefits in yield obtained from spraying DMI and QoI 2
fungicides on maize have already been described (Da Costa and Boller, 2008; Blandino et al., 2012), it has also been found that the response of the yield to fungicides is very complex, especially if the disease severity is low and the yield expectations are high (Paul et al., 2011; Wallhead, 2012). Moreover their impact on grain yield, in relation to different environmental conditions, has not been clearly reported. Both grain yield and quality, here intended as kernel hardness, are related to the photosynthetic leaf area (Nutter and Littrell, 1996), its activity, and its duration after flowering (Eik and Hanway, 1966; Waggoner and Berger, 1987), which in turn is negatively related to disease development and crop senescence. The aim of this research was to evaluate whether an improvement in grain yield could be obtained after the spraying of a mixture of DMI and Qol fungicides under different environmental conditions and whether the application of this fungicide could also positively affect some kernel quality parameters, such as grain hardness, thus offering a higher economic value to farmers and to the food chain.
MATERIALS AND METHODS Experimental Site and Treatments The study of the effect of foliar fungicide spraying on grain yield and quality was performed over four growing seasons, from 2009 to 2012. The field experiments were performed each year in two sites in northwest Italy characterized by different soil textures and fertility levels: Saluggia (45°14´ N, 8°00´ E, altitude of 194 m), in a shallow and sandy-loam soil, with distributions of sandy, silty, and clayish matter of 560 g kg1, 290 g kg1, and 130 g kg1, respectively, Typic Hapludalfs (USDA classification) organic matter 12 g kg–1; Villafranca, 44°47´ N, 7°33´ E, altitude of 253 m), featuring a deep and fertile siltyloam soil, Typic Eutrochrepts (USDA classification), with a soil texture composed of 190 g kg1 sand, 690 g ka1 loam, and 120 g kg1 clay, organic matter 23 g kg1. The choice of these two locations, both suitable for irrigated intensive maize cultivation, was made to compare the effect of the fungicide on grain yield and quality under different agronomic conditions. Irrigation was conducted using the furrow surface method, according to the typical farm management system, to prevent drought stress until the dough stage (GS 87). The average number of irrigations performed during the growing season was 8 to 9 in the sandy soil and 1 to 2 in the loam soil. At each site in each year, the field experiment was arranged in a randomized complete block design with four replications. Each plot consisted of 12 rows 0.75-cm apart and 15-m long. The plot alleys, orthogonal to the maize rows, were 1-m wide. Both locations were set up under natural E. turcicum inoculum conditions. The applied fungicide was a mixture of QoI and DMI fungicide: azoxystrobin and propiconazole (Quilt Excel). The formulation type is an emulsifiable concentrate sold by Syngenta Crop Protection AG. It was sprayed at 0.141 and 0.122 kg a.i. ha1, respectively (1 L of commercial product ha1). Two fungicide application timings (T1, T2) were compared with an untreated control (T0) in each site and in each
www.crops.org
crop science, vol. 55, july– august 2015
Table 1. Main trial information and fungicide application date for the field experiments. Saluggia 2009 Treatment† T1 T2 Planting date Harvest date †
2010
Villafranca 2011
2012
2009
2010
2011
2012
—————————————————————————————— Date of fungicide application —————————————————————————————— Jun 6 Jun 4 May 30 Jun 5 Jun 6 Jun 11 May 30 Jun 4 Jun 24 Jun 23 Jun 20 Jul 7 Jun 18 Jun 28 Jun 20 Jun 27 Apr 22 Apr 9 Apr 1 Mar 28 Apr 9 Apr 1 Apr 9 Mar 24 Sep 28 Sep 21 Sep 12 Sep 17 Oct 1 Sep 30 Sep 22 Sep 17
T1, application at the beginning of stem elongation (GS 30); T2, application at tassel emergence (GS 51).
year. The fungicide treatments were applied once in each trial, at the following growth stages, according to the development of the untreated control (T0): T1: the beginning of stem elongation (GS 30), at the feasible height limit to allow a common farm ground sprayer to be used T2: tassel emergence (GS 51) The treatments were performed using a self-propelled ground sprayer (Eurofalcon E140, Finotto) with a hydraulically adjustable working height that allowed the crop to be correctly sprayed till the end of stem elongation. Flat-fan nozzles were used to spray a volume of 400 L ha1 at a pressure of 200 kPa with a median droplet size range of 145 to 225 µm. A fan was used to blow low-pressure air toward the crop, while the nozzles were spraying, to increase the penetration of the water treated inside the canopy. The operation speed was 10 km h1. The planting and harvest dates as well as the fungicide treatments are reported in Table 1 for each year and site. The maize hybrid used for the experiment was Syngenta NX7034: FAO maturity class 600; 128 d to maturity; 1600 growing degree days (GDDs) to harvest with grain moisture of 250 g kg1. Planting was performed after a proper setting of the seedbed, which consisted of 30-cm-deep ploughing and disk harrowing. The experimental fields received 250, 100, and 100 kg ha1 of N, P2O5, and K 2O, respectively, each year. Weed control was conducted at pre-emergence with mesotrione (0.15 kg a.i. ha1), S-metolaclor (1.25 kg AI ha1), and terbuthylazine (0.75 kg AI ha1) (Lumax, Syngenta Crop Protection S.p.A.). To restrain damage to the ears by European corn borer (Ostrinia nubilalis Hübner) at GS 75 (milk stage), all the fields were treated with the pyrethroid lambda-cyhalothrin insecticide (Karate Zeon, Syngenta Crop Protection S.p.A.) at a dosage of 0.019 kg a.i. ha1.
Crop Measurements All the crop measurements were performed on the two middle rows of each plot. Fifteen randomly selected plants were evaluated for NCLB incidence at the milk stage (GS 75) and dough stage (GS 85). Five leaves were observed from each plant: the ear leaf, two leaves above, and two below. Northern corn leaf blight incidence refers to the percentage of leaves showing symptoms of the development of fungal disease. The ears were collected by hand from 7.5 m 2 (2 rows × 5 m) and the harvest was performed 15 d after the occurrence of physiological maturity (GS 87), which was calculated when the 1500 GDD threshold from planting time was reached. This crop science, vol. 55, july– august 2015
made it possible to evaluate whether different kernel dry-down conditions occurred during the experiments. All the collected ears passed through an electric sheller to obtain the grain weight. The grain yield was then corrected to the commercial moisture level of 140 g kg1. A subsample of 1 kg was put aside for the subsequent quality tests. Unfortunately, a heavy windstorm damaged most of the plants in the Villafranca field (silty soil location) in August 2012, and only the NCLB incidence was therefore measured and reported for this trial.
Kernel Quality Parameters and Hardness Test All the collected grain samples were dried after the harvest process at 60°C for 72 h to reduce the kernel moisture content to 100 g kg1. All the samples were then stored in a cold room at 7°C and 30% relative humidity until required. The samples were equilibrated to room temperature (24°C) and moisture (air humidity 60%) in paper bags before each test to the kernels was performed.
Thousand Kernel Weight The thousand kernel weight (TKW) test was performed by weighing 200 kernels free from defects. Two analytical replicates were performed for each sample.
Test Weight The test weight (TW) was performed using a Dickey-John GAC2100, and it was recorded as kg hL1. Two analytical replicates were performed for each sample.
Grain Protein Content Approximately 300 g of maize from each sample was ground to fine flour using a Retsch Mill ZM 200 fitted with a 1-mm screen. The grain protein content (GPC) was estimated using an near infrared reflectance (NIR) spectroscopy (Foss-NIR Systems). The protein content was then adjusted to a 100 g kg1 moisture content, which had been predicted by the NIR reflectance spectroscopy. Since TW and GPC cannot fully describe kernel hardness (Blandino et al., 2013), two specific methods, the floating test (FLT) and total milling energy (TME) were applied to obtain further information about this kernel quality feature.
Floating Test This test assesses the density of grain kernels: the number of kernels floating in a variable density solution (floaters) was
www.crops.org 3
Table 2. Total rainfall, rainy days, and growing degree days (GDD) from May to October and in the last 15 d before the harvest date (BH) from 2009 to 2012 in both sites. Saluggia Year 2009 2010 2011
Month
Rainfall
Rainy days
GDD
Rainfall
Rainy days
GDD
mm
No.
mm
No.
438
58
S °C d1 1868
369
53
S °C d1 1919
Last 15 d BH
81
10
126
107
9
125
May–Oct
728
77
1696
590
77
1653
Last 15 d BH
33
4
126
40
7
105
May–Oct
383
66
1888
373
63
1832
8
6
185
11
3
173
338
65
1892
400
78
1833
17
4
151
44
4
145
May–Oct
Last 15 d BH 2012
May–Oct Last 15 d BH
recorded, according to the method reported by Blandino et al. (2013). The floating test measures the area underneath the precipitation curve. This parameter is therefore correlated inversely to the kernel density. Two analytical replicates were performed for each maize sample.
Total Milling Energy This test was performed according to the method described by Blandino et al. (2013) and Ma and Dwyer (2012). A 20-g kernel sample was ground by means of a Culatti micro-hammer mill (Labtech Essa) fitted with a 2-mm screen. The instantaneous power consumption during the milling test was measured and recorded. This parameter was measured three times for each sample.
Statistical Analysis The normal distribution and homogeneity of variance were verified on the dependent variables by performing the Kolmogorov-Smirnov normality test and Levene test, respectively. The NCLB incidence values had previously been transformed using y’ = arcsine√x ´ 180/π, as percentage data derived from counting. An analysis of variance (ANOVA) was used to compare NCLB incidence, TKW, TW, and GPC, using a completely randomized block design in which the fungicide treatment and site were independent variables, whereas the year was a random factor. Since the homogeneity of variance was not verified considering all the trials together, ANOVA was used to separately compare the grain yield and moisture, TME, and FLT for each year using a completely randomized block design in which the fungicide treatment and the site were the independent variables. When necessary, multiple comparison tests were performed according to the Ryan-Einot-Gabriel-Welsh F (REGWF) method. SPSS Version 20.0 for Windows statistical package was used for the statistical analysis.
RESULTS Weather Trend Table 2 shows the total rainfall, the number of rainy days, and the temperature (expressed as GDD) from May to October and in the last 15 d before the harvest for each trial. On average, Saluggia (sandy-loam soil) had higher
4
Villafranca
temperatures during the growing season, especially in the last 15 d before the harvest, than those recorded at Villafranca (silty-loam soil). The total rainfall was quite similar in both sites for the same growing season. In 2009 there was very little rain during the growing season, and the rainy days were concentrated in the last part of the ripening stage, above all in the last 15 d before the harvest. The 2010 growing season was the coolest at both sites and was characterized by a higher number of rainy days. The 2011 and 2012 growing seasons were instead drier, with very little rainfall at the end of ripening. The average rainfall during the last 15 d before harvest was 20 mm, whereas during the 2009 and 2010 growing seasons it was 68 mm.
Northern Corn Leaf Blight Development The development of NCLB symptoms on leaves was influenced mainly by the growing season (Table 3 and Table 4). The incidence of disease on the leaves showed an increasing trend in each trial, from the milk (GS 75) to the dough stage (GS 85). The lowest incidence of the disease was recorded for the 2009 growing season, with only 3.5% of leaves showing symptoms during dough stage. This was followed by 2010, which, however, reported the highest disease incidence at the milk stage (7.1%) (GS 75). The highest NCLB attacks were observed in 2011 and 2012; for both years the incidence of leaves showing symptoms during the dough stage assessment was 32%. On average, the experiments in Villafranca showed a higher NCLB development than those in Saluggia at both the milk and dough stages, +124% and +82%, respectively. The fungicide treatment significantly reduced (P < 0.001) the NCLB incidence during both the milk and dough stages. The later application timing (T2) was more effective than the application at the beginning of stem elongation (T1). During the dough stage, the untreated plots showed 33% of NCLB symptoms, whereas fungicide application at GS 51 (T2) reduced the disease incidence to 13%. The interaction between the treatment and environment (site and year) was never significant.
www.crops.org
crop science, vol. 55, july– august 2015
Table 3. P values and standard error of means (SEM) on the effect of site and fungicide treatment on the northern corn leaf blight (NCLB) incidence measured during the milk and dough stage, thousand kernel weight (TKW), test weight (TW), and grain protein content (GPC). P values
NCLB Milk incidence stage NCLB Dough incidence stage TKW TW GPC
Treatment (B)
A´B
Site
Treatment
