Corn Growth Stages Research Articles

Variable rate nitrogen management in corn: Response in two crop rotations

Decision-making criteria to accurately predict nitrogen (N) rates in corn (<i>Zea mays</i> L.) would greatly benefit canopy sensor-guided variable rate N (VRN) management with positive implications for water quality. The objectives of this study were to measure corn yield response to VRN applied at the midvegetative corn growth stage and compare yield and agronomic efficiency (AE) between a one-time spring-N application (preplant or early sidedress) and two VRN management strategies, split-N (VRN^S) and rescue-N (VRN^R). Field sites located across Iowa received spring-N fertilizer at six application rates, with additional N potentially applied with each VRN spring-N rate and for the VRN^S and VRN^R strategies at the V10 growth stage based on canopy sensing. Drought conditions were evident during 2012 and 2013 in Iowa, which resulted in reduced corn yield and requirement for N fertilizer at many site-years. The VRN with 0 and 56 kg N ha⁻¹ (50 lb N ac⁻¹) applied in the spring was most closely aligned with calculated economic optimum N rate and AE. The VRN^S and VRN^R strategies applied more N than was needed, compared to spring-N only. Canopy sensors did not detect adequate to excess N, and therefore N applied prior to VRN application should be part of sensing-based algorithm criteria. Mean corn yield with the soybean (<i>Glycine max</i> [L.] Merr.)–corn rotation was not maintained with VRN when no spring-N was applied. Yield comparison showed no differences between spring-N, VRN^S, and VRN^R for both rotations. However, the greatest AE was achieved with spring-N and the VRN^S strategy in the soybean–corn rotation. Weather events that occur during and after canopy sensing and VRN application remain an important factor for successful corn yield response to N rate and timing, and should be considered with canopy sensor VRN. Results from this study provide feedback on how to translate remote sensing data into VRN management.

Light Quality Effect on Corn Growth as Influenced by Weed Species and Nitrogen Rate

&lt;p&gt;Corn-weed competition has often been characterized as the competition for limited resources such as light quantity, water, and nutrients. However, growing evidence suggests that light quality, specifically the red:far red ratio (R:FR), is a crucial component to corn-weed interactions. Additionally, a reduction in the R:FR has shown to down-regulate plant genes similarly to a nitrogen (N) deficient environment. A greenhouse study was conducted to evaluate the effect of N stress and R:FR from common waterhemp, velvetleaf, and volunteer corn on corn growth and development. The R:FR for all three weed species tended to be similar but lower than a weed-free treatment. However, observations from the spectral response curves demonstrated significant changes in the patterns of light reflected from each weed species. In the N-sufficient environment, early-season (V5 corn growth stage) R:FR from all three weed species reduced corn height, leaf chlorophyll content, and shoot biomass while increasing fibrous root biomass. However, in the N-deficient environment, no effects were observed on corn growth from changes in light quality, indicating N stress was a greater limiting factor. These results highlight the importance of the critical weed-free period and the need for proper early-season weed management.&lt;/p&gt;

Effect of microbial‐based inoculants on nutrient concentrations and early root morphology of corn (Zea mays)

AbstractMicrobial‐based inoculants have been reported to stimulate plant growth and nutrient uptake. However, their effect may vary depending on the growth stage when evaluated or fertilizer applied. Thus, the objective of this study was to test the hypothesis that microbial‐based inoculants known to promote root growth and nutrient uptake will promote plant growth, enhance early root development, and increase nutrient concentrations of corn (Zea mays L.). Plants were evaluated at four different growth stages and in the presence of three different nitrogen (N) fertilizers. The microbial‐based treatments evaluated were: SoilBuilder™ (SB), a filtered metabolite extract of SoilBuilder™ (SBF), a mixture of four strains of plant growth‐promoting Bacillus spp (BM), and a water‐inoculated control. The experiment also included four fertilizer treatments: urea (U), urea‐ammonium nitrate (UAN), calcium‐ammonium nitrate (CAN), and an unfertilized control. Corn plants were evaluated at growth stages V2, V4, V6, and VT. Plant growth parameters for biomass, height, and SPAD readings were enhanced by the three microbial‐based treatments. A greater effect of microbial‐based treatments was observed when plants were evaluated at V6 and VT stages. Parameters of early root development such as total root length (TRL), root surface area (RSA), and length of fine roots were enhanced when microbial‐based treatments were applied. Concentrations of N, P, and K were also increased by microbial‐based treatments compared to the non‐inoculated control. Increases in plant N concentration due to microbial‐based treatments were on average 72% for CAN, 61% for UAN, 72% for urea, and 54% for the unfertilized control. Phosphorus concentration was increased most (138%) when BM was applied with CAN. In the same way, when CAN was present, K concentration was increased by 95% with BM and 65% when SB and SBF were applied. Overall, the results demonstrate that microbial‐based inoculants evaluated in this study can positively impact corn growth and nutrient concentration, especially during the late vegetative stages. Furthermore, the results indicate that the enhancement of nutrient concentrations (N, P, and K) in this case was related to the capacity of microbial‐based treatments to impact root morphology at early stages of corn growth.

Management of Large, Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) in Corn

Palmer amaranth is a very problematic weed that has evolved resistance to several classes of herbicides, including 5-enolypyruvylshikimate-3-phosate synthase–inhibiting herbicides and photosystem II–inhibiting herbicides. In recent years, corn producers have had difficulty controlling large Palmer amaranth (&gt; 20 cm) in corn &gt; 30 cm whether it be due to environmental conditions or management failures. Palmer amaranth management in corn this tall is made even more challenging because atrazine is not labeled POST in corn &gt; 30 cm tall. Therefore, a study was conducted in 2013 and 2014 in Jackson, TN, to evaluate herbicide programs in corn &gt; 30 cm tall for the control of glyphosate-resistant Palmer amaranth &gt; 20 cm tall. Treatments consisted of herbicides applied alone and in mixtures with dicamba plus diflufenzopyr. Herbicides were applied POST to corn between the V5 and V6 growth stages. Dicamba plus diflufenzopyr 28 d after application controlled Palmer amaranth &gt; 87%. The herbicides alone or in combinations applied as tank mixtures did not improve control (&lt; 76%) over dicamba plus diflufenzopyr alone. There were no grain-yield differences among treatments because of Palmer amaranth control. This was likely due to the Palmer amaranth competition having already affected corn yield by the V5 to V6 corn growth stages.

Effect of zinc salt solutions on the development of chlorophyll and formation of seeds of maize hybrids

Zinc as an element is considered as one of the most limiting nutrients for crop production, mainly for cereals in the arid areas of the world. The article explores the impact of zinc salts at different concentrations on the course of physiological biochemical processes, germination and development of nine investigated hybrids of maize. In particular, we investigate how zinc nitrate solutions influence physiological biochemical processes of different maize hybrids. It is established that high concentration of zinc salt solution can arrest or inhibit processes of plants growth, exerting an effect typical of heavy metals. The influence of 0.01% and 0.02% of zinc nitrate aqueous solution on the content of chlorophyll and number of seeds on the stalks of different corn hybrids was studied. The results of experiments in which germinating seeds were placed in Petri dishes containing 0.01% and 0.02% nitrate zinc solutions showed that zinc in these quantities stimulates the synthesis of chlorophyll in the leaves in all studied hybrids, thereby stimulating plant growth. Thereafter, low concentrations of salt solutions of the same element stimulated all development processes. Zinc enters the active enzyme centers and participates directly in chlorophyll synthesis. The spray of solutions as foliar fertilizers at critical stages of corn growth increases the number of seeds, the diameter and length of stalk in the early ripening hybrids group, compared with the control. It was shown that lack of zinc affects the formation of seeds. The results of the field experiments showed that corn foliar feeding with 0.01% sodium nitrate increased productivity of the studied hybrids. Symptoms of zinc deficiency develop throughout the whole plant or are localized on the old lower leaves. At first, brownish grey and purple-coloured spots appear on the leaves of the lower and middle layers and then spread over the rest of the plant. The tissue of the areas like these simply dies off. Zinc deficiency had a negative effect on seeds production. From the results of experiments it follows that there are fluctuation of chlorophyll in maize hybrids when germinated in 0.01% and 0.02% salts solutions of zinc nitrate, and that the resistance of the plants to fungus and bacterial infections is strengthened when their seeds are previously treated with nitric acid zinc at 0.01% concentration.

Larval western bean cutworm feeding damage encourages the development of Gibberella ear rot on field corn.

A 2 year study was conducted to determine whether western bean cutworm (Striacosta albicosta Smith) (WBC) larval feeding damage increases severity of the fungal disease Gibberella ear rot [Fusarium graminearum (Schwein.) Petch] in field corn (Zea mays L.). The effect of a quinone-outside inhibiting fungicide, pyraclostrobin, on Gibberella ear rot severity and mycotoxin production, both with and without WBC pressure, was also evaluated. The impact of each variable was assessed individually and in combination to determine the effect of each upon ear disease severity. There was a positive correlation between the presence of WBC larvae in field corn and Gibberella ear rot severity under inoculated conditions in the 2 years of the experiment. An application of pyraclostrobin did not impact Gibberella ear rot development when applied at corn growth stage R1 (silks first emerging). Feeding damage from WBC larvae significantly increases the development of F. graminearum in field corn. We conclude that an effective integrated management strategy for Gibberella ear rot should target the insect pest first, in an effort to limit disease severity and subsequent mycotoxin production by F. graminearum in kernels. © 2016 Society of Chemical Industry.

Relación entre el peso freco y el peso seco del rastrojo de maíz en diferentes estados fenológicos del cultivo.

The amount of dry matter produced during various stages of corn growth is a important variable to be taken into consideration. However, the lack of drying facilities makes its measurement a difficult task in the fields. A simple method to convert the fresh weight of a crop in the field into dry weight, could be an answer to that problem. In this study, we calculated the relationship between fresh and dry weight of corn stovers, over several, growth, stages of eight corn cultivars of different vigour and maturity period, at two Mexican locations. The differences between cultivars were for percent stover dry weight (%SDW) most evident in the second half of the grain growth stage, when late cultivars showed less humidity than the early ones. The % SDW was regressed against the phenological developmental stage and expressed as a ratio against antesis (R, days to sampling /days to 50% antesis). The equations (R2 = 0.97 - 0.99) with best results were: Early maturing cultivars: %SDW = 12.6 + 0.94R2 + 1.68R4; Late: %SDW = 16.1 - 4.00 R2 + 3.36R4. There were no consistant differences among cultivars with different vigour levels, even though certain differences were noted among the locations and they were attributed to differences in relative humidity. We describe a protocol for determining the dry weight of corn stover by area unit (t/ha) when drying conditions are not available, by utilizing only a scale and a ruler.We also suggest a method to calculate percent dry matter for a real plant parts (including grain).

Influences of Rainfall Intensity and Leaf Area on Corn Stemflow: Development of a Model

As an important pathway for movement of rainfall or sprinkler irrigation water through a crop canopy to the ground, stemflow is of great significance for utilization efficiency of sprinkler irrigation water and for crop growth. In this study, under simulated indoor artificial rainfall, the stemflow rates (SF) of corn plants (Zea mays) in different corn growth stages (V4 stage ∼ VT stage) under different rainfall intensities (I) were observed, and the relationships among stemflow, leaf area (LA), and I were analyzed. Based on these results, stemflow models were developed. The results showed that for all corn growth stages, the average SF of a single corn plant was about 55.69 mL/min, accounting for 45% of total rainfall. SF increased as a power function of corn LA and I, and the percentage of stemflow in total rainfall increased as a power function of corn LA. Theoretical, semi‐empirical, and empirical models of corn SF and stemflow proportion (SR) of total rainfall were established by analyzing the relationships among LA, I, and stemflow. All three models were used to estimate SF and SR in different corn growth stages and achieved desired accuracy. The semi‐empirical and empirical models were more accurate in predicting and simulating corn SF, but the calculation and application of the semi‐empirical model was relatively simpler. The empirical model of SR enabled a more accurate calculation of the percentage of stemflow in total rainfall.

Use of corn height measured with an acoustic sensor improves yield estimation with ground based active optical sensors

Corn height measured manually has shown promising results in improving the relationship between active-optical (AO) sensor readings and crop yield. Manual measurement of corn height is not practical in US commercial corn production, so an alternative automatic method must be found in order to capture the benefit of including canopy height into in-season yield estimates and from there into in-season nitrogen (N) fertilizer applications. One existing alternative to measure canopy height is an acoustic height sensor. A commercial acoustic height sensor was utilized in these experiments at two corn growth stages (V6 and V12) along with AO sensors. Eight corn N rate sites in North Dakota, USA, were used to compare the acoustic height sensor as a practical alternative to manual height measurements as an additional parameter to increase the relationship between AO sensor readings and corn yield. Six N treatments, 0, 45, 90, 134, 179, and 224kgha−1, were applied before planting in a randomized complete block experimental design with four replications. Height measurement using the acoustic sensor provided an improved yield relationship compared to manual height at all locations. The level of improvement of the relationship between AO readings multiplied by acoustic sensor readings and yield was greater at V6 growth stage compared to the V12 growth stage. At V12, corn height measured manually and with the acoustic sensor multiplied by AO readings provided similar improvement to the relationship with yield compared to relating AO readings alone with yield at most locations. The acoustic height sensor may be useful in increasing the usefulness of AO sensor corn yield prediction algorithms for use in on-the-go in-season N application to corn particularly if the sensor height is normalized within site before combining multiple locations.

Effects of Crops on Runoff and Soil Loss on Sloping Farmland Under Simulated Rainfall

Crops are the most important sloping farmland cover. Runoff plot experiments were conducted to study soil erosion from a 10° gradient with different growth stage of corn and soybean by simulated rainfall. The results showed that compared with the bare slope, corn plants could averagely reduce 24% runoff and 47% soil loss and soybean plants could averagely reduce 31% runoff and 55% soil loss. With crop growth, runoff and sediment yield on the slope covered by crops decreased gradually and the fluctuation in the production process of runoff and sediment decreased and tended to be stabilized. On the slope covered by corns, runoff rate, sediment yield, and sediment concentration showed the negatively linear functional relationship with leaf area index. Under soybean coverage conditions, slope runoff showed the logarithmic functional relationship with leaf area index, while sediment yield and sediment concentration showed the exponential relationship with leaf area index. Under corn coverage conditions, soil loss ratio was 0.53 on average and showed the linear functional relationship with leaf area index. Under soybean coverage conditions, soil loss ratio was averaged 0.46 and showed the exponential functional relationship with leaf area index. Crops showed strong inhibitory effects on soil erosion and the effect on sediment interception was more significant than the effect on runoff impoundment. Soybean showed more significant effects on sediment interception and runoff impoundment than corn.

Polymer‐Coated Urea Improved Corn Response Compared to Urea‐Ammonium‐Nitrate When Applied on a Coarse‐Textured Soil

Increasing economic and environmental concerns in corn (Zea mays L.) production have prompted the need for improved N management. In this study, effects of two N sources [urea‐ammonium‐nitrate (UAN) and polymer‐coated urea (PCU)] on corn response were evaluated at different N rates over three site‐years. An additional N treatment of split‐applied UAN (UAN‐SP) based on the University of Nebraska‐Lincoln recommendation algorithm was also included. Leaf chlorophyll was indirectly measured using a chlorophyll meter at different corn growth stages for all N treatments to determine in‐season corn N status. Both PCU and UAN‐SP increased grain yield compared to UAN, even when the UAN rate was higher than that of PCU or UAN‐SP. The PCU treatment applied at 168 kg N ha−1 was as effective as UAN‐SP applied at ∼200 kg N ha−1. At early growth stages, leaf chlorophyll was higher in a dry year than in wet years, when more N loss was likely. At different growth stages taken individually or together, chlorophyll meter readings were significantly correlated to grain yield. Temporal N release from PCU in the conditions of this study was not an issue, as shown by the consistently greater chlorophyll meter readings in PCU treatments than in UAN treatments, regardless of interannual climatic variations. These results indicate that PCU consistently performed better than UAN.

Development of a Damage Function Model for Pratylenchus penetrans on Corn.

The lesion nematode Pratylenchus penetrans is a common pest of corn in the north-central United States. There are relatively few studies documenting the impact of Pratylenchus spp. on grain yield even though they are recognized as pests of corn and the target of commercial seed treatments. We adapted a component error modeling approach to develop a damage function for P. penetrans that included the influence of year and site in the yield loss relationship. Field data from six site-years was used to derive panel data consisting of all pairwise comparisons of the difference in nematode population densities and the associated proportional yield difference. Fourteen regression models of the relationship between proportional yield loss and the difference in nematode density were developed from soil and root assays at different corn growth stages. Seven models were significant: four models based on nematode population densities in soil (initial and final samples) and three based on nematode densities in seminal roots (corn growth stages V1 to V2 and V6) and adventitious roots (corn growth stage R1 to R2). The model we consider to be the most important, that based on the initial soil assay, estimated the yield loss caused by each nematode to be 0.0142%. The grand mean of the 118 plots we sampled implied a yield loss of 3.79%. The random effects of year and field did not contribute significantly to any of the models but were close to significance for some, suggesting a benefit from larger data sets. Experimental error was the largest component of the variance for all of the models; therefore, the damage function is more useful for demonstrating impact of P. penetrans rather than for accurately predicting yield loss at the field level. All of the fields in our study were an irrigated loamy sand soil, with grain yields above the county average; therefore, it is possible that our damage function is conservative. The value of soil sampling has been questioned for P. penetrans and this study shows it to be equal to if not better than root assays for predicting yield.

Growing degree days – Ecosystem indicator for changing diurnal temperatures and their impact on corn growth stages in Kansas

Understanding how climate change will affect plant phenology (shifts in the timing of plant activity) is central to many ecological and biogeochemical studies. This aspect of plant ecology often has been overlooked, but addressing the consequences of climate change for adaptive/mitigative management is now high on the list of priorities for funding agencies. This study is innovative because it uses growing degree days (GDD), which has existed since the 1730s, as an ecosystem indicator to study changing diurnal temperatures; their effects on different plant growth stages in the last century; and as a basis for development of future adaptive management strategies. Our results show the most recent time period (1980–2009) had the earliest emergence and the least variability among stations in the day at which the crop stage occurred for most stages except emergence and physiological maturity. 100 year linear trends in the stations indicated all seven crop stages except tassel initiation occurred earlier by one day per decade during the study period. The number of stations with significant decreases varied from 11 to 17 stations out of 23 stations in Kansas. Tassel initiation stage occurred later by one day per decade during the study period. The most recent time period (1980–2009) had the highest variability among stations and 30 year time periods. The variability in trends is higher in western Kansas when compared to eastern Kansas. This knowledge has transformative potential to improve our understanding of the occurrence and duration of the different plant growth stages, add local precision to earlier findings for changes in overall GDD that encompassed larger areas, and help explain the differences in trends from some earlier studies. These shifts in the phenology of agricultural plants as a result of climate change have implications on food production increases required to feed the growing population.

Subdoses do ácido 2-cloroetilfosfônico em estádios vegetativos da cultura do milho

O uso de maturadores tem sido prática comum na cultura da cana-de-açúcar. A aplicação destes produtos ocorre muitas vezes por meio de pulverização aérea, o que aumenta as chances de ocorrer deriva das moléculas do maturador em outras culturas, como o milho. Visando estudar possíveis fitointoxicações no milho ocasionadas por deriva de ethephon, foi realizado um experimento em campo com o objetivo de avaliar o efeito de subdoses do maturador quando aplicado nos estádios de desenvolvimento V4 e V8 da cultura do milho. O experimento foi instalado no delineamento com blocos casualizados, com quatro repetições. Os tratamentos foram arranjados em esquema fatorial 2 x 5, com primeiro fator correspondente aos estádios de desenvolvimento do milho em que foi aplicado o maturador (V4 e V8) e o segundo fator foi referente às subdoses de ethephon (0; 14,26; 28,51; 42,77 e 57,02 g ha-1 i.a.). Efeitos de fitotoxicidade visual não foram perceptíveis quando se aplicou as subdoses nos estádios V4 e V8 de desenvolvimento da cultura do milho. Da mesma forma, as características agronômicas e a produtividade de grãos não foram alterados por subdoses de até 57,02 g ha-1 i.a. de ethephon.

Nitrogen Competition between Corn and Weeds in Soils under Organic and Conventional Management

Crop yields can be similar in organic and conventional systems even when weed biomass is greater in organic systems. Greater weed tolerance in organic systems may be due to differences in management-driven soil fertility properties. The goal of this experiment was to determine whether soil collected from a long-term organic cropping system with a diverse crop rotation and organic fertility inputs would support higher soil nitrogen (N) resource partitioning, as indicated by overyielding of corn–weed mixtures, than a cropping system with a less diverse crop rotation and inorganic N inputs. A replacement series greenhouse experiment was conducted using corn : smooth pigweed and corn : giant foxtail proportions of 0 : 1, 0.25 : 0.75, 0.5 : 0.5, 0.75 : 0.25, and 1 : 0 and harvested at 29, 40, or 48 d after experiment initiation (DAI). The monoculture density of corn was 4 plants pot−1and the monoculture density of each weed species was 36 plants pot−1. Corn was consistently more competitive than both weed species at 40 and 48 DAI when soil inorganic N was limiting to growth. Corn–smooth pigweed mixtures had greater shoot biomass and shoot N content than expected based on the shoot biomass and shoot N content of monocultures (i.e., overyielding) at the onset of soil inorganic N limitation, providing some evidence for N resource partitioning. However, soil management effects on overyielding were infrequent and inconsistent among harvest dates and corn–weed mixtures, leading us to conclude that management-driven soil fertility properties did not affect corn–weed N resource partitioning during the early stages of corn growth.

Foliar application of nano-Fe3O4 induced Iron Content and Phytase Activity in corn seed Single Cross 704

Abstract. This study was conducted in an experimental field in a randomized complete block with three replications in Urmia, West-Azarbayjan province of Iran. Foliar application nano Fe3O4 was performed at 3 stages of corn growth, knee stage, vegetative growth and grain filling. Corn seeds after harvested, were soaked and then germinated and dried. Iron content and phytase activity were determined. The results of this study revealed that foliar application of nano Fe3O4 significantly induced iron concentration and the activity of phytase (P<0.01). The results of this study showed that nano iron oxide fertilizers enhances the quality of corn seeds by decreasing phytate content and increasing Iron concentrations.

Effects of Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) Feeding Injury on Sweet Corn Yield and Quality.

The brown marmorated stink bug, Halyomorpha halys (Stål), is an Asian species that now dominates the stink bug complex in many cultivated crops throughout the mid-Atlantic United States. Sweet corn (Zea mays L.) is a preferred host of H. halys, and the bug can cause kernel injury on developing ears. Currently, there is limited information available on which plant growth stages are most sensitive to H. halys feeding or density of bugs required to cause yield and quality reductions on processing and fresh market sweet corn ears. In 2011 and 2012, sweet corn ears were infested at three different corn growth stages: silking (R1), blister (R2), and milk (R3) at densities of zero, one, three, and five H. halys adults per ear for 7 d. At harvest, four yield measurements were assessed and ears were inspected for quality reductions. The greatest yield loss from H. halys occurred when infestations were initiated during early stages of ear development, and the greatest quality reductions (damaged kernels) occurred during later stages of ear development. A density of one H. halys per ear resulted in levels of kernel damage great enough to cause significant quality reductions. This study highlights the ability of H. halys to cause substantial economic losses in both fresh market and processing sweet corn in a relatively short period of time at low population densities. Therefore, infestations by this insect in sweet corn must be considered when making pest management decisions in regions where it has become established.

Species Composition and Abundance of Stink Bugs (Hemiptera: Heteroptera: Pentatomidae) in Minnesota Field Corn.

In response to concerns of increasing significance of stink bugs (Hemiptera: Heteroptera: Pentatomidae) in northern states, a survey was conducted over 2 yr in Minnesota to characterize the Pentatomidae associated with field corn, Zea mays L. Halyomorpha halys (Stål), an exotic species, was not detected in this survey, despite continued detection of this species as an invader of human-made structures in Minnesota. Five species of Pentatomidae (four herbivorous; one predatory) were collected from corn. Across years, Euschistus variolarius (Palisot de Beauvois) and Euschistus servus euschistoides (Vollenhoven) had the greatest relative abundances and frequencies of detection. In 2012, the abundance of herbivorous species exceeded 25 nymphs and adults per 100 plants (i.e., an economic threshold) in 0.48% of fields. However, the abundance of herbivorous species did not reach economic levels in any fields sampled in 2013. The frequency of detection of herbivorous species and ratio of nymphs to adults was highest during reproductive growth stages of corn. The predator species, Podisus maculiventris (Say), was detected in 0 to 0.32% of fields. These results provide baseline information on the species composition and abundance of Pentatomidae in Minnesota field corn, which will be necessary for documentation of changes to this fauna as a result of the invasion of H. halys and to determine if some native species continue to increase in abundance in field crops.

Soil Quality Dynamics during Different Growth Stages of Corn (Zea mays, L.) Cultivation in Sri Lanka

Soil Quality Dynamics during Different Growth Stages of Corn (Zea mays, L.) Cultivation in Sri Lanka

THE EFFECT OF WINTER CATCH CROPS ON WEED INFESTATION IN SWEET CORN DEPENDING ON THE WEED CONTROL METHODS

An experiment was carried out in east-central Poland (52°06’ N, 22°55’ E) over 2008– 2011 to study the effect of winter catch crops on the weed infestation, number, and fresh matter of weeds in sweet corn (Zea mays L. var. saccharata). The following winter catch crops were grown: hairy vetch (Vicia villosa Roth.), white clover (Trifolium repens L.), winter rye (Secale cereale L.), Italian ryegrass (Lolium multiflorum L.) and winter turnip rape (Brassica rapa var. typica Posp.). The catch crops were sown in early September and incorporated in early May. The effect of the catch crops was compared to the effect of FYM (30 t·ha-1) and control without organic manuring (NOM). Three methods of weed control were used: HW – hand weeding, twice during the growing period, GCM – the herbicide Guardian Complete Mix 664 SE, immediately after sowing of corn seeds, Z+T – a mixture of the herbicides Zeagran 340 SE and Titus 25 WG applied at the 3–4-leaf stage of sweet corn growth. Rye and turnip rape catch crops had least weeds in their fresh matter. Sweet corn following winter catch crops was less infested by weeds than corn following farmyard manure and nonmanured corn. Least weeds and their lowest weight were found after SC, BRT and VV. LM and BRT reduced weed species numbers compared with FYM and NOM. The greatest weed species diversity, determined at the corn flowering stage, was determined after SC and FYM. The number and weight of weeds were significantly lower when chemically controlled compared with hand weeding. The best results were observed after a post-emergent application of the mixture Z+T. The weed species diversity on Z+T-treated plots was clearly lower compared with GCM and HW.