Ear Leaf Research Articles

Advantages of Intercropping Soybean with Maize Under Two Maize Plant Distributions and Three Mineral Nitrogen Fertilizer Rates

The advent of further bioengineering for growing soybean with maize holds only promise for the future of the crop intensification field. The present research studied responses of maize crop and its yield attributes to decrease mineral nitrogen (N) inputs by growing soybean with two maize plant distributions under three cropping systems. Local maize variety T.W.C. 310 was grown under intercropping and sole cultures in one row/ridge in one and two plants/hill spaced at 30 and 60cm, respectively, that received three mineral N fertilizer rates (4, 5 and 6 g N/plant), while local variety of soybean seeds Giza 82 were drilled in two rows/ridge. A split – split – plot design with three replications was used. Light intensity with in maize canopy, ear leaf N and indole acetic acid (IAA) contents were affected by all the studied factors. Mixed pattern increased grain yields per plant and per ha by 1.56 and 3.98 %, respectively, in comparison with sole culture in addition to yielding 1.74 ton/ha of soybean. Increasing number of plants from one to two plants/hill by increasing plant spacing from 30 to 60 cm increased grain yields per plant and per ha. There were no significant differences between the medium and the highest mineral N fertilizer rates for all the studied traits. Soybean improved N use efficiency (NUE) for maize plant of mixed pattern. The mixed pattern had a total yield increase of 29.79 % than sole maize. Growing soybean on both sides of maize ridge that distributed to two plants/hill spaced at 60 cm decreased 47.6 kg N/ha of the recommended mineral N rate of maize plants which formed the best bioengineered treatment under Egyptian conditions.

Development of Weather Based Forewarning Model for Major Pests of High Altitude Rainfed Rice Agroecosystem

Studies were conducted to develop weather based forewarning model for the major pests of high altitude rice viz., green leaf hopper (GLH), brown plant hopper (BPH), leaf folder, yellow stem borer and ear head bug. Three field trials were conducted at Hybrid Rice Evaluation Centre, Tamil Nadu Agricultural University, Gudalur, The Nilgiris, Tamil Nadu during Kharif 2010 to 2012. Results revealed that the population of GLH and BPH started from first and second week of September, respectively and leaf folder and yellow stem borer damage started from third week of September and continued till harvest (December) of the crop. Ear head bug population was noticed during first week of October coinciding flowering of the crop with a peak during December first week and persised up to the harvest. The results of correlation and multiple regression analysis revealed that the population of GLH, BPH, ear head bug, leaf folder and stem borer damage had exerted a significant positive association with maximum temperature and significant negative association with morning relative humidity and rainfall. However, the influence of minimum temperature and evening relative humidity was not significant and 80, 81, 92, 67 and 76 per cent of variation in the population of GLH, BPH, ear head bug, leaf folder damage and stem borer damage, respectively was influenced by weather parameters. The multiple regression equation fitted with weather parameters to predict the GLH population is Y = -2.28 + 0.416 X1 - 0.043 X3 – 0.018 X5, BPH population is Y = 62.73 + 0.28 X1 – 0.67 X3 – 0.010 X5, leaf folder damage is Y = 248.23 – 1.22 X2 – 2.35 X3 + 0.04 X5, yellow stem borer damage is Y = 29.09 + 0.32 X1 -0.36 X3 – 0.002 X5, ear head bug population is Y = 26.64 – 0.253 X2 – 0.234 X3 – 0.005 X5. where, X1 - maximum temperature (oC), X2 - minimum temperature (oC), X3 - morining relative humidity (%), X4 - Evening relative humidity (%) and, X5 - rainfall (mm)

Effect of Ethephon and Nitrogen Fertilizer on Nitrogen Uptake, Nitrogen Use Efficiency and Yield of Summer Maize

A field experiment using maize hybrid Zhengdan 958 was conducted to study effect of ethephon (0 and 180 g ha) and nitrogen fertilizer (0, 75, 150, and 225 kg N ha) on summer maize yield and yield components, nitrogen uptake, nitrogen use and SPAD value. The results showed that ethephon significantly decreased nitrogen uptake and N uptake efficiency, whereas markedly increased N utilization efficiency. N agronomic efficiency under ethephon treatment was 32.7%–34.6% more than that under control, and ethephon had no negative effect on maize yield and yield components. With increase nitrogen fertilizer of application, maize yield, yield components and nitrogen uptake were increased, but N uptake efficiency, N utilization efficiency, N partial factor productivity and N agronomic efficiency were decreased. Nitrogen uptake under 225 kg N ha treatment was 68.4%–91.8% more than that under 0 kg N ha. However there was no difference for nitrogen uptake between 225 kg N ha and 150 kg N ha treatments. Significant effect of ethephon × nitrogen was observed on nitrogen uptake, N uptake efficiency and N agronomic efficiency. Ethephon as well as higher nitrogen rate increased SPAD value of ear leaf during grain filling stage, while there was no significant interaction between ethephon and nitrogen fertilizer on SPAD value. Correlation analysis indicated that summer maize yield was significantly positively correlated with nitrogen uptake at silking stage and harvest stage and with SPAD value of ear leaf.

Maize nutrient uptake affected by genotype and fertilization

The content of nutrients in maize are commonly related with fertilization and soil quality and rarely explained with the individual hybrid properties. Therefore, the aim of this study is to access a long term fertilization system on ear leaf of Mg, Fe, Mn and Cu content in six maize hybrids(NS 3014, NS 4015, NS 5043, NS 6010, NS 6030 and NS 7020). Samples were collected from a long-term experiment at the Rimski Sancevi experimental field of the Institute of Field and Vegetable Crops in Novi Sad. The study included maize monoculture and 2-year rotations with the application of NPK and manure. Results showed that ear Mg content was influenced with the treatments, hybrid and their interaction and ranged from 1.77-2.69 g kg-1. Iron variability was significantly affected with the treatments and interaction (hybrid x treatments) in range from 103.2 to151.9g kg-1. The ear manganese content (41.1-63.6g kg-1) derived from treatments and hybrid effect and Cu (12.3-23.6 g kg-1) was significantly influenced with treatments. Across all treatments, in average, NS6030 had higher values of nutrient and NS3014 was lower in ear nutrient content. This indicates that vegetation length could favor nutrient accumulation. Obtained results suggested that even on fairly productive soil such as Chernozem hybrid selection and the balanced fertilization is crucial for managing the maize nutrient content.

Ear Leaf Photosynthesis and Related Parameters of Transgenic and Non-GMO Maize Hybrids

Hybrid maize (Zea maysL.) through transgenics now includesδ-endotoxins for insect control and tolerance to the herbicides glyphosate and glufosinate. Some hybrids have multiple transgenic traits as part of their genotype (stacked gene). Limited information is available on how these traits alone affectA(net assimilation rate;µmol CO2m−2s−1) and related physiological parameters. A two-year, two-location, irrigated experiment comparing four stacked gene, four glyphosate tolerant, and two non-GMO hybrids for ear leafA,gs(stomatal conductance; mol H2O m−2s−1),Em(transpiration; mol H2O m−2s−1), IWUE (intrinsic water use efficiency;(A/(gs*100))), and Ci(intercellular [CO2]µmol CO2mol air−1) was completed at Stoneville, MS, in 2012. Data were collected at growth stages R1 (anthesis) and R2 (early kernel filling) using a Li-Cor LI-6400XT set at 355 μmol mol−1CO2with a flow rate of 500 μmol s−1and a 6400-02 light source set at 87.5% full sunlight. Measurements were made between 08:30 h and 11:30 h CST, within 48 h of 25 ha mm irrigation and ≥33.0% cloud cover. Transgenic traits did not influence the physiological parameters ofA,gs,Em, IWUE, or Ciduring the critical growth stages of R1 or R2.

Effects of Ethylene-Chlormequat-Potassium on Leaf Nitrogen Assimilation after Anthesis and Early Senescence under Dif-ferent Planting Densities

To explore the effects of ethylene-chlormequat-potassium (ECK) on the physiological mechanisms of nitrogen assimilation and early senescence in summer maize, and provide a theoretical basis for high and stable yields of summer maize under high plant density by chemical regulation technology in North China Plain, we conducted a field experiment using two varieties of Zhongdan 909 and Xundan 20 with different planting densities in 2013 and 2014. The results showed that increasing plant density significantly decreased the activities of nitrate reductase (NR) and glutamine synthetase (GS) after anthesis, glutamate oxaloacetic transaminase (GOT) activity at anthesis, and glutamate pyruvate transaminase (GPT) activity at 30 days after anthesis. The soluble protein and free amino acid contents at 20 days after anthesis, and the SPAD value at 10 days after anthesis were significantly decreased with increasing plant density. For both varieties, grain yield reached the highest under 7.5×10 plants ha, while decreased under the density of ≥ 7.5×10 plants ha. The higher density resulted in early senescence. ECK treatment significantly increased the activities of NR, GS, and contents of free amino acid, soluble protein and SPAD value during middle and late grain filling stages. ECK treatment also significantly improved the GOT and GPT activities under 7.5×10−10.5×10 plants ha. Under the density ≥ 7.5×10 plant ha, the yields of Zhongdan 909 and Xundan 20 compared with their own control were respectively 第 12期 卢 霖等: 乙矮合剂对不同密度夏玉米花粒期叶片氮素同化与早衰的影响 1871 increased by 5.59%−6.63% and 6.73%−8.10%. ECK treatment significantly increased the nitrogen assimilation key enzyme activity of ear leaf and its product content under different planting densities, promoted normal nitrogen assimilation and prevented early senescence under higher planting densities, therefore increased yield. Thus, an appropriate planting density combined with ECK application could be an important technique for achieving high grain yield for summer maize production in North China Plain.

Grain yield and phenotypic performances of maize inbreds under variable environmental conditions

According to regional reports on climate, more frequent and severe droughts and floods are already apparent. Modern maize breeding for different purposes (e.g. drought tolerance) emphasizes the importance for improved maize ability to withstand adverse environmental conditions. Genotypes with drought tolerance obtain high grain yield under optimal conditions and lower, but stable yield under dry environmental conditions. Field testing was conducted in 2014, on twenty-three maize inbred lines differing in drought tolerance. The inbreds were evaluated in respect to morphological traits (plant and ear height, total number of leaves, number of leaves above uppermost ear, ear leaf length and width), yield components and grain yield per plant. The experiment was set up according to RCB design with two replications. To simulate water stress, two plant densities were applied. According to Principal Component Analysis and cluster analysis, five inbred lines (T1, T2, T4, T8 i T15) performed the highest stability in both experimental conditions. Those inbreds could be used as a source for drought tolerance in breeding programs.

Effect of Foliar Boron Fertilization of Fine Textured Soils on Corn Yields

Boron (B) is an essential micronutrient needed for normal plant growth and development. To evaluate the response of corn to foliar B applications at V4–V6 (4–6 leaves with visible collars) and VT (tasseling) growth stages on fine textured soils, a field experiment was conducted at four sites from 2008 to 2010 in Northeast Missouri. The treatments included a non-treated control; V4–V6 applied B at 0.56, 1.12 and 2.24 kg·ha−1; and VT applied B at 0.28, 0.56 and 1.12 kg·ha−1. Foliar B, applied at V4–V6 at 2.24 kg·ha−1, resulted in higher yields than VT applications. No significant differences in yield were found for B applications at different timings for concentrations of 0.56 and 1.12 kg·ha−1. Boron applied at V4–V6 and 2.24 kg·ha−1 increased yield 0.29 Mg·ha−1 compared to the non-treated control. The B applications at VT increased ear leaf tissue B concentration compared to V4–V6 applications and non-treated control, but it had no significant effect on corn yields. No significant difference between B treatments was observed for grain oil, protein, starch or extractable starch concentration; severity of anthracnose stalk rot or common rust; and ear tip fill. The B application of 2.24 kg·ha−1 at V4–V6 decreased the severity of gray leaf spot, but increased the severity of northern leaf blight compared to the non-treated control. Boron applied at V4–V6 at 2.24 kg·ha−1 was the most beneficial timing and concentration evaluated in these fine textured soils.

Optimum leaf removal increases canopy apparent photosynthesis, 13C-photosynthate distribution and grain yield of maize crops grown at high density

Excising the upper leaves strata of maize crops cultivated at high stand densities could possibly optimize canopy architecture to achieve enhanced canopy apparent photosynthesis, a more favorable distribution of 13C-photosynthates to grain, and ultimately higher grain yields. To test this hypothesis, we conducted a leaf removal experiment in 2012 and 2013 growing seasons in Shandong, a province in the North China Plain. Jinhai5, a corn cultivar planted widely across China, was grown at a density of 105,000plantsha−1 until 3 days after silking (DAS), when plants were subjected to the removal of the uppermost and next leaves (S2), the four uppermost leaves (S4) or the six uppermost leaves (S6), with no leaf removal as control (S0). In the S2 treatment we found a longer duration of canopy apparent photosynthesis (CAP) and green leaf area index (LAI), higher total dry matter weight at physiological maturity as well as greater harvest index (HI) compared to the control, whereas those in the excessive leaf removal treatments (S4 and S6) declined substantially. In addition, modification of the number of leaves above the ear leaf led to different patterns of allocation of 13C-photosynthates. Excising two leaves promoted the distribution of 13C-photosynthates to grains, while that allocation decreased in the S4 and S6 treatments, which can be interpreted as a result of increased retention of 13C-photosynthates in the stem and ear bracts. Plants in S2 treatment displayed a yield advantage under high plant density due to higher kernel weight and more harvested ears. Relative to control, plants in the S2 treatment had 15% and 12% higher grain yields in 2012 and 2013, respectively. However, the removal of four or six leaves at the very early grain filling period, when kernel sink capacity is being established, caused a marked reduction in yields due to decreased both kernel number per plant and kernel weight, despite a relatively higher biomass availability per kernel. In conclusion, excising two leaves (the uppermost and next leaves) of maize crops cultivated at high plant density delayed leaf senescence, enhanced canopy photosynthesis and dry matter accumulation, leading to a higher post-silking source–sink ratio with its positive impact on kernel weight and higher grain yield.

English

Chlorophyll closely related to photosynthetic capacity and developmental stage in crops. In order to reveal the genetic characters of chlorophyll content in leaf above ear, ear leaf and leaf under ear (three-ear-leaves) of maize, ten inbred lines from five different heterotic groups were selected to make crosses by a completely diallel cross design. The combining ability analysis and genetic parameters estimations of chlorophyll content of three-ear-leaves were carried out. The results showed that highly differences existed among ninety F1 crosses including reciprocal crosses, the general combining ability (GCA) effects and special combining ability (SCA) effects were different and p<0.01. The inbred lines No.10 (Xu178), 1(Ye478) and 7(Dan340) were observed with positive GCA effects while other inbred lines showed negative GCA effects. The crosses 4×9 (Chang7-2×8085Tai) and 6×9 (Zi330×8085Tai) with significantly positive SCA effects were found. The cross 4×6 (Chang7-2×Zi330) appeared maximum negative SCA effect for three-ear-leaves investigated in this study. The GCA effect of inbred lines was not corresponding to the SCA effect. The correlation coefficients between three-ear-leaves were all more than 0.7 which were highly positive correlations. Chlorophyll content showed reciprocal crosses differences (p<0.05). Broad sense heritability and narrow sense heritability were about 55 and 33.5% respectively. The additive effect was greater importance than non-additive effect. Key words: Maize, chlorophyll content, reciprocal effect, heritability.

How Much, Leaves Near the Ear Contribute on Yield and Yield Components of Maize?

Abstract In order to study the role of leaf position on yield and yield component of maize, this research was conducted based on randomized complete block design with three replicates at the research field of Urmia University, Urmia, Iran, in 2011. For determine the role of leaf position in maize yield, we used the leaf removing (clipping) treatments. Leaf clipping treatments contain ear leaf clipping, above ear leaf clipping, below ear leaf clipping and control (without leaf clipping) that imposed at one week after ear initiation. Leaf removing had a significant effect on all measured traits (number of seed per row, row number per ear, ear length, 1000 seed weight, seed yield, biological yield), except harvest index. Removing of above leaves decreased 6.68% the number of seeds on ear compare to control. The highest 1000 seed weight (274 g) was observed in plants without leaf clipping. Ear leaf clipping and below ear leaf defoliation ranked second for 1000 seed weight. Whereas plants without any leaf clipping had the utmost seed yield (8.77 t ha-1) but defoliating of leaf above ear lead to lower seed yield (6.77 t ha-1). Leaf removal above ear decreased 22.80% biological yield compared to control. The correlation analysis showed that all traits had positive correlation with seed yield. The most correlation was between ear length and number of row per ear (r=0.89**). Also, number of seed per row (r=0.71**), 1000 seed weight (r=0.67**), ear length (r=0.65**), biological yield and harvest index (r=0.59**) showed the most correlation with seed yield, respectively. Results revealed that the most reduction in all traits accrued in maize plants with above ear leaf clipping, this results indicated that the important roles of leaves position especially the role of above ear leaves in yield and yield components of maize.

Carbon assimilation, leaf area dynamics, and grain yield in contemporary earlier- and later-senescing maize hybrids

Maize breeding during the past 50 years has been associated with a delay of leaf senescence, but it is not clear whether this trait is likewise associated with higher grain yield in modern hybrids. Post-silking growth, leaf area dynamics, photosynthetic parameters and yield were compared in modern maize hybrids differing in canopy senescence rate. In the first two experiments, four hybrids were grown in the field at Balcarce, Argentina (37°45′ S, 58°18 W). In spite of differences in chlorophyll retention and photosynthesis of the ear leaf, post-silking growth and grain yield were very similar in all four hybrids while kernel N concentration was lower in the later-senescing hybrids. In a third experiment, a later-senescing (NK870) and an earlier-senescing (DK682) hybrid were grown to analyze the potential photosynthetic contribution of delayed leaf senescence. Leaf area and chlorophyll content were larger in NK870, especially at the lower canopy level (0.75m above the ground). However, hybrids did not differ for canopy light interception. Because photosynthetic photon flux density below 1m above the ground was less than 10% of incident radiation and photosynthesis quantum yield did not change during senescence, the potential photosynthetic output of lower leaves below 1m was very low. Lower leaves of NK870 had N concentrations higher than those needed to sustain photosynthesis at the light conditions below 1m. Therefore, we show that delayed senescence does not necessarily improve post-silking C accumulation because: (i) canopy light interception is not reduced by senescence except at very late stages of grain filling; (ii) contrasting hybrids show more pronounced senescence differences at canopy levels receiving less than 10% of incident radiation; (iii) delayed senescing hybrids present lower kernel N concentrations while extra N is retained in leaves exposed to a light limiting micro-environment. Delayed senescence at lower canopy levels may be unproductive, at least under non-stressing conditions.

Potential for transmission of Stenocarpella macrospora from inoculated seeds to maize plants grown under controlled conditions

Maize seeds infected by Stenocarpella macrospora can cause stalk and ear rot and leaf spot. Transmission of this pathogen through seeds may vary according to the cultivar, climatic conditions, and virulence of the pathogen among other factors. The aim of this study was to assess the transmission rate of S. macrospora from seeds of the maize cultivars C1-RB9308YG and C2-RB9108 using artificially infected seeds grown under two temperatures (20 ºC and 25 ºC). Seeds were inoculated by the osmotic conditioning method for 24 h (inoculum potential - P1), 48 h (P2), 72 h (P3) and 96 h (P4). After inoculation, 25 seeds were distributed individually in plastic cups with substrate, with 4 replicates per treatment. At the end of twenty-eight days of daily assessments, all plants were analyzed for the presence of the pathogen by biological methods, and some were sampled at random and analyzed Bio-PCR. The maximum percentages of dead seeds/seedlings in pre-emergence were 74.5% and 82.5% for P3 and P4, respectively. The highest total rate of transmission of the pathogen under study was 85.8% for seeds of the cultivar C1 at the highest inoculum potential (P4), grown at the temperature of 20 ºC.

An empirical model for changes in the leaf area of maize

Chen, G., Zhang, J., Liu, P. and Dong, S. 2014. An empirical model for changes in the leaf area of maize. Can. J. Plant Sci. 94: 749–757. Accurate predictions of the leaf area index (LAI) are critical for many crop growth simulation models and essential for simulating crop growth and yield. In this paper, we present a new empirical leaf area model that simulates LAI for different maize (Zea mays L.) varieties under different cultivation conditions. Based on leaf morphological development, the model describes the two processes of leaf growth: expansion and senescence. The effect of planting density and nitrogen on LAI was also simulated in the model. A nitrogen sensitivity parameter was used to distinguish the different varieties. The model predictions were compared with field measurements of LAI for four varieties under different conditions. The results showed that the new model can correctly simulate LAI for maize under different cultivation conditions. The sensitivity analyses revealed that the new LAI model was very sensitive to lle (the length of the ear leaf) and VN (fertilizer sensitivity parameters of cultivars). The new model facilitates the simulation of maize leaf growth and senescence at the population level.

Residual phosphorus effects and nitrogen × phosphorus interactions in soybean–maize rotations on a P-deficient Ferralsol

Legume-cereal rotations are an essential component of integrated soil fertility management in low-input cropping systems, but strategies are needed to increase phosphorus (P) fertilizer use efficiency in such systems. These may include preferential targeting of P to one of the crops in the rotation cycle, the use of P-efficient genotypes, and the optimization of the rates of P fertilizer used. A field trial was conducted to evaluate the effects of increasing P fertilizer rates (0, 11, 22 and 44 kg P ha−1, added as triple super phosphate) applied to three soybean genotypes grown on a P-deficient Ferralsol, on the nitrogen (N) and P nutrition of a subsequent maize crop. In addition, a greenhouse trial was set up to assess N, P and other rotation effects of three soybean genotypes on a subsequent maize crop relative to a maize–maize rotation at high and low P supply. In the field trial, soybean did not respond to increasing P rates, but residual P effects improved maize grain yields by up to 90 %. Ear leaf (field trial) and shoot (pot trial) P concentrations increased by applying N to maize, demonstrating important N × P interactions. The pot trial did not reveal a positive rotation effect of soybean on maize beyond the mere N-benefit, showing that soybean was not able to improve P availability to maize after correcting for the N-effect. No variation in rotation effects on maize among soybean genotypes was observed. Because of the absence of effects of the soybean crop on P availability to maize, opportunities to increase P fertilizer use efficiency in soybean–maize rotations mainly reside in maximizing P uptake by each crop separately and in matching P fertilizer rates with crop demand.

不同积温带间玉米花后叶片氮同化差异分析与化学调控

Northeast China is a key area for maize production,but the low temperatures often result in delayed maize growth and slow maturity,as well as low grain quality and high grain moisture. So,to help improve maize yield,we studied the effects of PASP-KT-NAA on maize leaf nitrogen assimilation characteristics after florescence over different accumulated temperature regions with Zhengdan 958 and Fengdan 3 maize seeds as materials,in Heilongjiang province. The protein content in maize leaves is low and the key enzyme activities of nitrogen metabolism are susceptible to changes in environment,such as frost harm,etc. For this reason,the effects of different temperatures and the PASP-KT-NAA mixture on maize NRA( nitrogen reductive activity) in leaf tissue has been studied in three different accumulated temperature zones in Heilongjiang province,during 2010—2011. In field experiments,the first zone trial plot is located in the science station of Heilongjiang academy of agriculture sciences in Harbin. Its general accumulated temperature is ≥2800℃,but the accumulated temperature in the maize growing season in 2010 and 2011 is 3154. 2℃ and 3004. 2℃,respectively. The second zone trial plot is located in the science station of Heilongjiang Academy of Agricultural Sciences in Suihua City. Itsgeneral accumulated temperature is ≥2600℃,but the accumulated temperature in the maize growing season in 2010 and2011 is 2901. 8℃ and 2885. 0℃,respectively. The third zone trial plot is located in Yi' an County. Its general accumulated temperature is ≥2400℃,but the accumulated temperature in the maize growing season in 2010 and 2011 is2728. 3℃ and 2602. 6℃,respectively. The results showed that:( 1) The NRA,NO-3content,leaf nitrogen content and chlorophyll content were affected by temperature,in zone order of IⅡⅢ. After PKN treatment,FDTR and ZDTR ear leaf NRA in the three accumulated temperature zone were significantly higher than that in the water control and leaf nitrogen content and chlorophyll content was higher than the water control. The average of the ear leaf free amino acid of the two maize varieties performed"up-down"trends with the growth process,and reached its maximum 20 d after florescence. The soluble protein of zone I tended to decrease with the growth process,with zones Ⅱ,and Ⅲ firstly increasing then decreasing with the growth process,reaching its maximum at 10 d after florescence. After PKN treatment,ear leaf free amino acid and soluble protein in samples from zone I,Ⅱ and Ⅲ were significantly higher than the water control;( 2) The grain yield of zone I was higher than that for zone Ⅱ and Ⅲ. PKN treatment raised grain yield higher than those of the water control. The increased rate of ZDTR yield in zones I,Ⅱ and Ⅲ in 2010 and 2011 were 3. 09% —8. 81%,4. 61% —10. 91%,5. 91% —13. 51%,respectively. The increased rate of FDTR yield in zones Ⅰ,Ⅱ and Ⅲ,in 2010 and 2011were 2. 43% —5. 19%,3. 03% —6. 01%,2. 57% —4. 62%,respectively. PKN treatment improved the maize ear leaf nitrogen assimilation key enzyme activity and its product content over different accumulated temperature regions,promoted nitrogen assimilation normally under low temperature conditions and eventually increased yield.

Evaluation of N sources, cover crops, and tillage systems for corn grown under organic management

Public demand for healthier foods and more sustainable food systems in the U.S. has triggered market prices and production of organic alternatives of major crops such as corn (Zea mays L.). Two cover crops and their interactions with tillage systems, N sources and N rates were studied to evaluate the possibility of using these agronomic practices to facilitate growing corn under organic management in Kentucky. A split-split plot design in a RCBD with four replications was evaluated in three environments (SP08, UKR08, UKR09). The main plot treatments were cover crops [hairy vetch, HV (Vicia villosa Roth) and rye (Secale cereale L.)], the split plots were tillage systems [no-till (NT) and moldboard plow (MP)], and the split-split plots were the N treatment factorial combinations including two N sources [Louisville Green (LG) and Nature Safe (NF)] at four rates of N (45, 90, 135 and 180 kg N/ha plus a common control). In addition we conducted a laboratory study of nitrate release for the two selected N sources. Results showed the MP/HV combination resulted in the highest yields at all experimental sites followed by HV/NT. Ear leaf N and grain N content were higher under HV compared with rye at all sites. Nature Safe as N source, increased ear leaf N and grain N more than LG in all experimental sites, and increased yield at two of the three environments. Laboratory incubation studies showed that both N sources stopped mineralizing at 28 days after application, releasing, 55 kg N/ha on average. The MP/HV/NF treatment combination was the best management combination for organic corn production in the environments we studied.

Diurnal dynamics of maize leaf photosynthesis and carbohydrate concentrations in response to differential N availability

Diurnal changes of the carbohydrates in maize leaves reflect transitions in photosynthesis, carbohydrate metabolism and translocation rates, and can provide insights into the control of carbohydrate export from source leaves. Relationships of diurnal courses of leaf photosynthetic rates (A), nonstructural carbohydrates (NSC), and ear dry matter accumulation were investigated in field grown maize under different nitrogen (N) regimes. Nitrogen applications increased plant N uptake and grain yield as well as leaf area, chlorophyll content and soluble protein concentration. No differences in A among N treatments were observed during periods of low light intensities early and late in the day. The largest difference of A among N treatments appeared at 12:00PM at silking, and shifted to 15:00PM at 15 and 30 days after silking (DAS). In general, leaf glucose levels tended to be lower in N fertilized than unfertilized plants. At silking, the diurnal pattern of glucose was similar to that of A, reaching a peak between 9:00AM and 12:00PM. Clear diurnal pattern of leaf sucrose and starch concentrations were found at each sampling date, albeit less pronounced as development progressed from silking, to 15 and 30 DAS. Sucrose concentrations were lower in unfertilized than in N fertilized plants for most of the 24-h cycle at all three developmental stages. At silking and 15 DAS, starch concentrations were significantly greater in unfertilized compared to N fertilized plants. Ear leaf NSC dynamics observed here suggest that factors (i.e. source–sink dynamics) other than carbon assimilation limit maize yield under low N conditions.

Assessment of maize response to Minjingu phosphate rock and triple superphosphate applied under different P-application strategies in a Ferralsol in Tanzania

Phosphorus undergoes many reactions in acid soils, most of which convert it to less-available forms. There is a need to search for P source and P-application strategies that minimize the unfavourable reactions and optimize the benefits derived from P application. A field experiment was conducted in a Ferralsol for three years (2004–2006) to compare the effectiveness of Minjingu phosphate rock (MPR) with triple superphosphate (TSP) as assessed by maize response. The same experiment compared two P application strategies, i.e. P recapitalization and seasonal P application strategy, and two P rates, namely a standard P rate (SPR) and half of the SPR. The experiment followed a randomized complete block design with nine treatments replicated four times. Both P sources increased yields, nutrient P and Ca uptake significantly (p < 0.05) over the control, but the difference between sources was not significant. Both P sources increased the P concentration in ear leaf to the critical range ≥ 0.2% in all three seasons. Cumulative yields were comparable in the two P-application strategies. Both P sources had high residual effects whereby grain yield increments in the 2006 season ranged from 1 to 2 t ha−1. Hence, MPR can substitute for TSP without yield reduction in Ferralsols. The seasonal P-application strategy was comparable with the P recapitalization, thus either can be chosen.

Foliar copper uptake by maize plants: effects on growth and yield

A slight increase in the levels of a certain nutrient can cause a significant increase in crop yield or can cause phytotoxicity symptoms. Thus, the aim of this study was to evaluate the effect of foliar application of copper (Cu) on the growth and yield of DG-501 maize. The experiment was carried out between December 2009 and April 2010 in conventional tillage. When plants were with six to eight leaves, Cu (0, 100, 200, 300, 400, 500 and 600g ha-1) was applied to the leaves. Treatments were arranged in randomized complete block with five replications. When 50% of the plants were in flowering, it was evaluated the plant height, culm diameter, height of the first ear insertion, leaf area, and chlorophyll content. At harvest, it was evaluated diameter and length of the ear, yield and thousand grain weight. There was a linear reduction in the plant height and in the height of the first ear insertion with increasing Cu doses. On the other hand, chlorophyll content, leaf area, diameter and length of ear, thousand grain weight and yield increased at doses up to 100g ha-1 Cu, however, decreased at higher doses. Therefore, foliar Cu application at doses higher than 100g ha-1 has toxic effect in maize plants with losses in growth and yield.