Maize Plant Density Research Articles

Extending growing period is limited to offsetting negative effects of climate changes on maize yield in the North China Plain

Climate changes in temperature, solar radiation, and precipitation potentially interrupt progressive improvement in crop yield. Genetic and agronomic strategies to adapt climate changes were proposed in previous studies, but were rarely evaluated. In this study, meteorological data from 1954 to 2014 at one representative station in the North China Plain (NCP), model simulation of Hybrid-Maize, and a field experiment were combined together to detect climate change impacts on maize yield and to assess the adaptive effects of cultivars. Three maize cultivars with contrasting lengths of growing period were grown at three specific plant densities. Cultivar with a long growing period (LG) was grown at 67500 (optimal density), 82500, and 97500 plant ha−1, medium-growing (MG) cultivar at 82500 (optimal), 97500, and 112500 plant ha−1, and short-growing (SG) cultivar at 97500 (optimal), 112500, and 124500 plant ha−1. During the past six decades, temperature increased and solar radiation decreased significantly in the total, vegetative, and reproductive growing periods of maize in the NCP with a slight decline in precipitation. These climate changes significantly reduced yield at a rate of 30.8, 31.3, and 25.0kgha−1yr−1, respectively, for SG, MG, and LG maize cultivars. Decline in growing degree days (GDD) use efficiency of LG cultivar with changing climate was one-fold slower than that of SG and MG cultivars. MG maize cultivar was estimated to produce the highest grain yield in NCP owing to its relatively long growing period and high tolerance of plant density. LG maize cultivar has a larger potential to adapt changing climate, but has a larger difficulty in improving yield because of lower tolerance of high plant density. Improvement of plant architecture in space and in time is expected to resolve the conflict between adapting climate changes and tolerating high plant density in maize.

Living Mulch for Sustainable Maize Stover Biomass Harvest

The Renewable Fuels Standard mandate provides enhanced opportunity for maize (Zea mays L.) stover use as a bioenergy feedstock. Living mulch (LM) offers a possible solution for the natural resources constraints associated with maize stover biomass harvest. A two‐site‐year study was conducted near Boone and Kanawha, IA, in both maize following maize (MM) and maize following soybean [Glycine max (L.) Merr.] (SM) sequences to evaluate the impact of established and chemically suppressed Kentucky bluegrass (Poa pratensis L.) ‘Ridgeline’, ‘Wild Horse’, ‘Oasis’, and ‘Mallard’ blend and creeping red fescue (Festuca rubra L.) ‘Boreal’ as LM on three maize hybrids (population sensitive, population insensitive, and yield stable). Maize grain yield for the no LM treatments in the MM and SM sequences was 12.0 and 13.2 Mg ha−1, respectively, at Boone and 12.8 and 14.8 Mg ha−1, respectively, at Kanawha, 23 to 73% greater than the LM treatment. Ethanol yield (L ha−1) was 12 to 119% greater, protein concentration was ≤9% greater, and starch concentration was ≤1% lower in the no LM treatment maize than in LM treatment maize. Maize hybrid by cover interaction was significant for parameters including total aboveground biomass and protein concentration at Boone, with inconsistent maize hybrid responses to the LM system. Stover yield, stover quality, stover C and N, leaf area index, maize plant density, maize maturity, and sequence year in the MM sequence were also evaluated. Results emphasize the need for maize hybrid and LM system compatibility, as well as effective LM suppression techniques.

Adjusting maize plant density to different climatic conditions across a large longitudinal distance in China

Climatic conditions, including temperature range and solar radiation, are closely linked to maize (Zea mays L.) growth and development. Adjusting plant density is one of the most effective measures for maximizing maize yield under different climatic conditions. The objectives of this study were (1) to determine the optimum plant density as well as the corresponding leaf area index (LAI) and yield in different maize producing regions in China and (2) to learn how climatic conditions influence maize growth and grain yield. The 3-year (2013–2015) field experiment used a hybrid maize cultivar (‘Zhengdan 958’) with six plant density treatments: 4.5, 6, 7.5, 9, 10.5, and 12plantsm−2. Three different ecological regions were chosen for the study: Gongzhuling (Jilin Province, China), Yinchuan (Ningxia Hui Autonomous Region, China), and Qitai (Xinjiang Uygur Autonomous Region, China). Comparing the same plant density treatment at different sites, grain yield and dry matter accumulation decreased in the order Qitai>Yinchuan>Gongzhuling. The optimum plant densities (i.e., treatments with greatest yield) were 12plantsm−2 at Qitai, 10.5plantsm−2 at Yinchuan, and 7.5plantsm−2 at Gongzhuling. At the optimum plant density, the LAIs at silking and physiological maturity were, respectively, 8.94 and 4.27 at Qitai, 7.50 and 1.85 at Yinchuan, and 6.18 and 1.67 at Gongzhuling. Climatic factors, especially solar radiation and diurnal temperature range, exerted significant influences on maize yield. These observations will be useful for determining best management practices for maize production under different climatic conditions across large areas and for providing helpful suggestions for maize breeders.

Effects of maize roots on aggregate stability and enzyme activities in soil

Soil aggregation and microbial activities within the aggregates are important factors regulating soil carbon (C) turnover. A reliable and sensitive proxy for microbial activity is activity of extracellular enzymes (EEA). In the present study, effects of soil aggregates on EEA were investigated under three maize plant densities (Low, Normal, and High). Bulk soil was fractionated into three aggregate size classes (>2000μm large macroaggregates; 2000–250μm small macroaggregates; <250μm microaggregates) by optimal-moisture sieving. Microbial biomass and EEA (β-1,4-glucosidase (BG), β-1,4-N-acetylglucosaminidase (NAG), l-leucine aminopeptidase (LAP) and acid phosphatase (acP)) catalyzing soil organic matter (SOM) decomposition were measured in rooted soil of maize and soil from bare fallow. Microbial biomass C (Cmic) decreased with decreasing aggregate size classes. Potential and specific EEA (per unit of Cmic) increased from macro- to microaggregates. In comparison with bare fallow soil, specific EEA of microaggregates in rooted soil was higher by up to 73%, 31%, 26%, and 92% for BG, NAG, acP and LAP, respectively. Moreover, high plant density decreased macroaggregates by 9% compared to bare fallow. Enhanced EEA in three aggregate size classes demonstrated activation of microorganisms by roots. Strong EEA in microaggregates can be explained by microaggregates' localization within the soil. Originally adhering to surfaces of macroaggregates, microaggregates were preferentially exposed to C substrates and nutrients, thereby promoting microbial activity.

Evaluation of intercropping groundnut (Arachis hypogaea L.) with maize under different plant densities in sandy soils.

Intercropping is the practice of growing two or more crops simultaneously on the same field to maximize total production per unit area. Intercropping is traditional practice in small holders especially at developing countries. The reason for this popularity is built on high profit and maximizing agriculture resources. Therefore, the objective of the present study is to evaluate the effect of intercropping maize with different plant densities on yield and yield components of groundnut to increase the productivity of groundnut under sandy soils. Two field trials were carried out at the experimental and research station at Ismailia (ARC) during 20013 and 20014 summer seasons. Maize variety SC168 and groundnut C.V. Giza.6 were used at the two seasons. The experimental design was a split plot design with three replicates; the main plots were assigned to three maize treatments (harvesting maize for grains, defoliation maize plants at 85 days from sowing maize and harvesting maize for silage). Three maize plant densities were distributed in sub plots by 2, 3 and 4 plants/hill at distance of 70 cm apart. Groundnut plants were sown in both sides of ridges (120 cm ridge width) by growing two plants per hill distanced at 20 cm apart under intercropping and solid2 (as intercropping) , in addition to recommended solid planting (solid1). Results could be summarized as follows: maize treatments, plant densities of maize and their interactions significantly affected groundnut characters. Removal maize plants for silage at 85 days or defoliation maize plants (at 104 days) increased light interception on groundnut plants which had a positive impact on the pod and seed yield of groundnut. Groundnut under intercropping with two maize plants per hill (50% of recommended density of maize) had the highest weight of seed per plant (13.18 and 12.78 g) and yield of pods per fed (12.02 and 11.63 ardab) at 2013 and 2014 season, but four maize plants per hill (100% of recommended density of maize) caused significant reduction of seed yields per plant and pod yield per fed. According to this investigation, to gain high productivity of groundnut (13.90 and 12.90 ardab/fed, at 2013 and 2014 season), remove maize plants as silage (at 85 days) and / or growing two maize plants per hill (50%) under intercropping in sandy soil. )ardab = 75 kg pods).

Plant density and fertilization in hybrid quality protein maize (Zea mays): Effects on the soil nutrient status and performance of succeeding wheat (Triticum aestivum) and productivity of cropping system

After introduction of hybrid under maize (Zea mays L.) cultivation in India it became competitive to rice and found suitable for crop diversification. Due to higher nutrient demand and differential plant type the hybrid needs modification in production technology especially for nutrient and plant geometry. So, this study was conducted in maize-wheat (Triticum aestivum L.) (MW) system in western Indo-gangetic plains in sandy loam soil for two consecutive years (2010-12) to explore best maize density and nutrient management in system in order to enhance soil nutrient status and productivity. The results showed that the application of the highest dose of nutrients in maize, i.e. 300: 45.9: 87.5 N:P:K kg/ha resulted in higher organic carbon, macro and micronutrient availability in soil while application of the lowest dose of fertilizer gave significantly higher CEC and available sulphur. Significantly higher CEC, organic carbon and available nutrients were observed in 66 000 plants/ha which gave significantly higher plant height and effective tillers in wheat. The growth and yield attributes of wheat, viz. plant height, effective tillers, spike length, spikelets/spike and spike weight in wheat were significantly higher with residual effect of 300: 45.9: 87.5 N:P:K kg/ha nutrient application in maize which were on par with 250: 39.9: 75.0 N:P:K kg/ha. Amongst the direct nutrient application in wheat significantly higher LCC, SPAD, plant height, effective tillers, spike length, spikelet/spike, and grain weight/spike were recorded with 125% RDF which were on par with RDF or 75% RDF. The better nutrition in maize compared to ad-hoc recommendations resulted in significant (P&lt;0.05) enhancement of system productivity by 17 to 19%. The direct application of nutrient in wheat gave 14 to 19 higher yield of wheat as well as 6 to 8% higher yield of the MW system. So, on the basis of two years study it was concluded that growing of maize with 66 000 plants/ha and 250:39.9:75 kg/ha N:P:K application followed by 90:19.8:24.0 kg/ha N:P:K application in wheat may be adopted for higher yield and soil nutrient status in western Indo-gangetic plains.

How High Plant Density of Maize Affects Basal Internode Development and Strength Formation

High plant density of maize (Zea mays L.) reduces the stalk quality of the basal internodes and increases stalk lodging. The objective of this experiment was to explore the mechanism by which plant density influences basal internodes. The morphological, mechanical, anatomical, and biochemical characteristics of the third basal internode were compared at three plant densities. High plant density increased internode length due to an increase in the rate of rapid elongation. High plant density decreased the duration of internode thickening and dry matter accumulation, causing the diameter and dry weight per unit length to decline. However, rind penetration strength (RPS) did not increase rapidly until after the termination of rapid morphological growth. The mid‐to‐late stage of dry matter accumulation was critical for RPS formation. The rapid increase in RPS was closely related to cellulose and lignin accumulation. High plant density reduced the rates of cellulose and lignin accumulation, which was adverse to the formation of cortex tissue and RPS. High plant density caused rapid elongation, thickening, and structural carbohydrate accumulation to begin and end earlier. These results indicate that measures should be implemented as early as possible in the growing season to increase lodging resistance at high plant density of maize. These measures need to reduce the rate of rapid internode elongation and increase the rate of rapid cellulose and lignin accumulation.

Effect of planting system of potato and plant density of maize on productivity of potato- hybrid maize intercropping system

The experiment was conducted at Agronomy Research Field, Bangladesh Agricultural Research Institute, Gazipur during 2010-11 to find out the appropriate planting system of potato and plant density of maize in potatohybrid maize intercropping system for maximum yield and economic return. Ten treatments were evaluated viz., T1= Potato whole tuber single row (75 cm × 20 cm) + 125% hybrid maize (75 cm × 20 cm), T2=Potato whole tuber single row (75 cm × 20 cm) + 100% hybrid maize (75cm × 25 cm), T3= Potato whole tuber single row (75 cm × 20 cm) + 83% hybrid maize (75 cm × 30 cm), T4= Potato half tuber paired row (20 cm/ 55 cm × 20 cm) + 125% hybrid maize (75 cm × 20 cm), T5= Potato half tuber paired row (20 cm/ 55 cm × 20 cm) +100% hybrid maize (75 cm × 25 cm), T6= Potato half tuber paired row (20 cm/ 55 cm × 20 cm) + 83% hybrid maize (75 cm × 30 cm), T7= Sole potato whole tuber single row planting system (60 cm × 25 cm), T8 = Sole potato half tuber paired row (20 cm/ 55 cm × 20 cm), T9= Sole hybrid maize in normal spacing 75 cm × 25 cm (sole HM1) and T10= Sole hybrid maize (75 cm × 25 cm) sown 30 days after potato planting (sole HM2). The results revealed that sole planting of both potato and maize produced the maximum yields. In case of sole potato, potato half tuber paired row planting system was better than potato whole tuber single row planting system. On the other hand, the performance of sole HM1 was better than sole HM2 in relation to growth, yield and economic performance. Over all T1 treatment ( potato whole tuber single row planting system with 125 % hybrid maize population) was the best intercropping system for getting higher yield and economic return as well as less relative crowding coefficient with better crop performance ratio.Bangladesh J. Agril. Res. 41(3): 397-409, September 2016

Assessing the contribution of weather and management to the annual yield variation of summer maize using APSIM in the North China Plain

Long-term field experimental data provides a good opportunity to evaluate the effects of different management practices and weather factors on maize yield. An 11-year field experiment (2003–2013) with the same maize cultivar and two short-term experiments including different sowing dates and plant densities were conducted at Luancheng Agro-ecological Experimental Station in the North China Plain (NCP). The measured pheonological development, biomass and grain yield were used to calibrate and validate the APSIM-maize model. The results showed that APSIM-maize model could capture the biomass and grain yield of summer maize under the various management practices and weather conditions. After calibration and validation, five scenarios were simulated using the APSIM model. The simulated results showed that weather factors including sunshine hours and the diurnal temperature range during the grain fill stage had the positive effects on maize yield. For different management practices, plant density was the most important factor which affected the maize yield. The optimal plant density was approximate 8.6plants/m2. Maize yield would be decreased with the sowing dates delayed after the middle of June. Meanwhile, earlier sowing before the end of May also reduced the grain production. The optimized sowing date and plant density could reduce the seasonal yield variation of maize caused by the weather factors. The findings of this study suggest that the maize plant density should be properly increased and sowing time should be optimized according to the harvesting of its previous crop.

Morphological Characteristics of Maize Canopy Development as Affected by Increased Plant Density

Improving crop productivity through higher plant density requires a detailed understanding of organ development in response to increased interplant competition. The objective of this paper is thus to investigate the characteristics of organ development under increased interplant competition. A field experiment was conducted to investigate organ development across 4 maize plant densities i.e. 2, 6, 12 and 20 plants m–2 (referred to PD2, PD6, PD12 and PD20 respectively). In response to increased interplant competition, lengths of both laminae and sheaths increased in lower phytomers, but decreased in upper phytomers. Sheath extension appeared to be less sensitive to increased interplant competition than lamina extension. Extension of laminae and internodes responded to increased plant density as soon as onset of mild interplant competition, but did not respond any further to severe competition. Both lamina width and internode diameter were reduced due to a smaller growth rate in response to increased plant density. Overall, this study identified that organ expansion rate can be taken as the key morphological factor to determine the degree of interplant competition.

Response of Sorghum halepense demographic processes to plant density and rimsulfuron dose in maize

SummaryIn spatially heterogeneous weed infestations, variable dose technologies could be used to minimise herbicide use; high doses could be applied to reduce high‐density patches and low doses to maintain weed populations in low‐density portions of a field. To assess the potential short‐ and long‐term effects of variable herbicide dose and site‐specific management, the major weed demographic processes were described and parameterised in this study. Various doses of rimsulfuron (from 0 to 12.5 g a.i. ha−1) were applied to different densities of Sorghum halepense (0–100 plants m−2). Contrary to similar studies with other weed species, higher herbicide efficacy was not observed at low densities, suggesting that the same rimsulfuron dose should be applied regardless of the S. halepense density. The highest percentage of control was obtained with the full rimsulfuron dose. However, it did not guarantee a decrease of the infestation in the following season in the field areas where the initial S. halepense density was lower than 60 plants m−2. Reduced doses of rimsulfuron to control S. halepense cannot be recommended based on our results.

Ecological intensification management of maize in northeast China: Agronomic and environmental response

Optimum field management practices need to be developed and improved to solve the challenge of increasing food production while retaining the ecological integrity of farming system underlying the goal of sustainable agriculture. In our study, the concept of ecological intensification (EI) was applied to a spring maize cropping system in Jilin province, China during 2009–2013. Results indicated that the average grain yield was 11.8tha−1 in the EI treatment; while the farmers’ practice (FP) treatment had an average of 11.4tha−1 grain yield across five seasons. The Hybrid Maize Model was used to simulate the potential yield under water-limited condition, and the results showed that grain yield with 92.6% of the average potential yield (14.3tha−1) in EI treatment was closer to the yield potential than FP treatment. Adjusted nitrogen (N) fertilizer rate, split-application of N at the right time and suitable recommended hybrid maize plant density were used for improving N use efficiency and decreasing the negative effects to the environment. Consequently, a total of 180kgNha−1 was enough for maize growth and resulted in equal plant N uptake as the 251kgNha−1 applied in FP. Higher agronomic efficiency of N (AEN), recovery efficiency of N (REN) and partial factor productivity of N (PFPN) in EI treatment (39.7kgkg−1, 66.1% and 66.2kgkg−1, respectively) were observed relative to those in FP treatments (26.9kgkg−1, 42.5% and 50.4kgkg−1, respectively). Improved N use efficiency contributed significantly less N loss to the environment. Our results showed that calculated residual Nmin, the apparent N loss and total GHG emission was 37.5%, 34.3% and 29.8% lower in EI treatment when compared to FP treatment. This study helps quantify and understand the concept and practices of EI. Adoption of 4R Nutrient Stewardship (fertilizer right source, right rate, time and placement) and supporting agronomic practices (optimizing plant density and plant hybrid selection) in our study optimized crop production and minimized potential environmental impact.

Response of Some Soybean Cultivars to Low Light Intensity under Different Intercropping Patterns with Maize

A two-year study was carried out at Mallawi Agricultural Experiments and Research Station, A.R.C., El-Minia governorate, Egypt, during 2014 and 2015 seasons to determine the compatible soybean cultivar with high maize plant density to achieve farmer's benefit under intercropping conditions. Alternating ridges (70 cm width) between maize and soybean were used as 1:3, 2:4, 2:2, 3:3 and 4:2, respectively, in addition to sole culture of both crops. Local maize cultivar T.W.C. 310 was grown in one plant per hill distanced at 30 cm under intercropping and sole cultures, meanwhile local soybean cultivars (Giza 22, Giza 82 and Giza 111) were drilled in both sides of the ridge (two plants/hill distanced at 15 cm) under intercropping and sole cultures. A split plot distribution in randomized complete block design with three replications was used. The results indicated that maize yield attributes were increased significantly by decreasing maize plant density from 67 to 25% of sole maize under intercropping conditions, meanwhile the converse was true for plant height and grain yield per ha. All the studied maize traits were not affected by soybean cultivars. Also, all the studied maize traits were not affected the interaction between intercropping patterns and soybean cultivars. Soybean yield and its attributes were increased significantly by decreasing maize plant density from 67 to 25% of sole maize under intercropping conditions except plant height. The late-maturing soybean cultivar Giza 22 recorded the highest values of intercepted light intensity within soybean canopy, number of pods per plant, seed index, seed yields per plant and per ha, meanwhile, the highest values of biological yield per ha, plant height and number of branches per plant were recorded for soybean cultivar Giza 111. Soybean cultivar Giza 22 gave the highest seed yield per plant compared to the other cultivars under all the intercropping patterns. Relative yield of soybean showed that the early-maturing soybean cultivar Giza 82 is better adapted to low light intensity than the other cultivars. Land equivalent ratio and area time equivalent ratio values for intercrops were greater than 1.00 indicating less land requirements of intercropping patterns than sole maize. Growing four maize ridges alternating with two ridges of soybean cultivar Giza 82 achieved the highest net return compared to sole maize.

Evaluation of Maize Nutrient Contents in a Maize/Cowpea Intercropping Systems in South Africa

Field experiments were carried out at three localities in North West and Limpopo provinces at South Africa to assess the effects of planting density and planting patterns and their interaction effects on residual soil nutrient contents in maize/ cowpea (M/C) sole and intercropped systems. The trial consisted of four planting densities (10000; 20000; 30000 and 40000 plants ha -1 ) and six planting patterns (1 rowM:1rowC; 1rowM:2rowsC; 2rowsM:2rowsC; 2rowM:4rowC; sole maize and sole cowpeas) at three sites. The experiment was a split-plot incorporated in randomized complete block design with four replications where maize plant density was the main factor and subplot factor was the planting pattern. The obtained results were as following: 1) Maize N, P, K, Ca and Mg concentration level showed a decreased pattern as the planting density increased at both trial sites. 2) Maize N content in planting density ranged from 1.28 to 1.65% at both locations. 3) Plant density of 10 000 plants ha -1 had higher N yield of maize by 22 and 11% relative to 40 000 plants ha-1 at Potchefstroom and Taung, respectively. However, N concentration in maize was significant at Taung, the 2rowsM:4rowsC pattern had higher N concentration and was 1.75% compared to all other intercropping planting patterns and sole maize. 4) The interaction of all intercropping planting patterns and plant density of 10 000 plants ha -1 gave higher nutrient concentration level than at higher plant density. 5) Sole cowpea had higher residual soil N-NO3- yield of 1.92, 1.66 and 1.23 mgkg -1 , whereas residual soil N-NH +4 was 3.28, 3.44 and 3.34 mgkg -1 at Syferkuil, Potchefstroom and Taung, respectively, compared to all intercropping planting patterns and sole maize. 6) Cowpea has the ability to fix atmospheric N into the soil for subsequent crop use. and 7) The study indicates that intercropping system and lower plant density up to 30 000 plants ha-1 of maize had the potential of improving crop productivity and soil fertility status depending on the climate and available N in the soil.

The Effects of Maize Planting Density and Weeding Regimes on Light and Water Use

Light and water are among essential resources required for production of photosynthates in plants. A study on the effects of weeding regimes and maize planting density on light and water use was conducted during the 2001/2 short and 2002 long rain seasons at Muguga in - the central highlands of Kenya. Weeding regimes were: weed free (W1), weedy (W2), herbicide (W3) and hand weeding twice (W4). Maize planting densities were 9 (D1) and 18 plants m -2 (D2) intercropped with Phaseolus vulgaris (beans). The experiment was laid as randomized complete block design replicated four times and repeated twice. All plots were thinned to 4 plants m -2 at tasseling stage (96 DAE) and thinnings quantified as forage. Soil moisture content (SMC), photosynthetically active radiation (PAR) interception, evapo-transpiration (ET crop), water use efficiency (WUE), and harvest index (HI), were determined. Percent PAR was higher in D2 than in D1 before thinning but higher in D1 than in D2 after thinning in both seasons. PAR interception was highest in W2 but similar in W1, W3 and W4 in both seasons. SMC was significantly lower in W2 but similar in W1, W3 and W4. D2 had lower SMC than D1 in season two. Weeding regime significantly influenced ET crop, while planting density and weeding regime significantly influenced WUE and HI. D2 maximizes water and light use for forage production but results to increased intra-specific plant competition for water and light severely before thinning (96 DAE) that reduce grain yield in dual purpose maize, relative to D1.

Row Arrangement, Phosphorus Fertility, and Hybrid Contributions to Managing Increased Plant Density of Maize

Inter‐plant competition must be carefully managed to realize the yield potential of increased plant density of maize (Zea mays L.). Twin row planting arrangement, P fertility, and hybrid selection may be important components of managing increased plant density. Our hypotheses were (i) that twin row planting arrangement would be superior to traditional 0.76‐m rows at ultra‐high densities and (ii) that supplemental P fertility would alleviate inter‐plant competition. In 2010 and 2011, twin row planting arrangement was compared to single 0.76‐m rows across densities ranging from 61,775 to 160,615 plants ha−1 and P fertility treatments ranging from 0 to 168 kg P2O5 ha−1. Twin rows did not increase yield relative to single rows, and twin rows often yielded significantly less at plant densities greater than 111,195 plants ha−1. Mean responses to supplemental fertility were 1.0 and 0.3 Mg ha−1 in 2010 and 2011, respectively. There was no interaction between plant density and P fertility suggesting that extra resource availability does not necessarily overcome inter‐plant competition. In 2011, two hybrids of contrasting ear type were included to explore the role of hybrid selection in plant density response. Maximum yields of each hybrid were achieved at contrasting densities, and genetic differences in plant density tolerance appeared to be related to (i) kernel number response on a per‐area basis and (ii) stability of individual kernel weight. These results highlight the importance of independently optimizing row spacing and soil fertility while understanding the plant density response characteristics of maize hybrids.

Maize yield and quality in response to plant density and application of a novel plant growth regulator

Farmers in China have gradually increased plant density in maize to achieve higher yields, but this has increased risk of lodging due to taller and weaker stems at higher plant densities. Plant growth regulators can be used to reduce lodging risk. In this study, for the first time, the performance of a mixture of the plant growth regulators ethephon and diethyl aminoethyl hexanoate (DA-6), called EDAH is tested at different plant densities and in different cultivars. Grain yield, yield components and grain quality as well as plant height and lodging percentage were determined in two years (2012 and 2013), using two maize hybrids, ZD 958 and Pioneer 335 at densities of 4.5, 6.0, 7.5 and 9.0plantsm−2 with and without foliar application of EDAH at 7 expanded leaves stage. EDAH significantly increased grain yield (by 7.8–8.0%), kernel number per ear (by 2.9–4.0%) and 1000-kernel weight (by 3.3–5.1%). Lodging percentage increased with plant density and was decreased by EDAH application in 2013. Optimal density was 7.5plantsm−2. The number of ears per unit ground area increased linearly with plant density, but number of kernels per ear and kernel weight showed an optimum. The two tested cultivars differed in yield and quality. No effects of EDAH on grain quality parameters (protein, oil and starch content) were found. We conclude that EDAH can improve lodging resistance and yield in maize, and that the yield effect of EDAH also occurs if lodging is not reduced.

Spatio-temporal dynamics of maize cropping system in Northeast China between 1980 and 2010 by using spatial production allocation model

Understanding crop patterns and their changes on regional scale is a critical re- quirement for projecting agro-ecosystem dynamics. However, tools and methods for mapping the distribution of crop area and yield are still lacking. Based on the cross-entropy theory, a spatial production allocation model (SPAM) has been developed for presenting spa- tio-temporal dynamics of maize cropping system in Northeast China during 1980-2010. The simulated results indicated that (1) maize sown area expanded northwards to 48°N before 2000, after that the increased sown area mainly occurred in the central and southern parts of Northeast China. Meanwhile, maize also expanded eastwards to 127°E and lower elevation (less than 100 m) as well as higher elevation (mainly distributed between 200 m and 350 m); (2) maize yield has been greatly promoted for most planted area of Northeast China, espe- cially in the planted zone between 42°N and 48°N, while the yield increase was relatively homogeneous without obvious longitudinal variations for whole region; (3) maize planting density increased gradually to a moderately high level over the investigated period, which reflected the trend of aggregation of maize cultivation driven by market demand.

Effect of Planting Methods and Plant Density on Yield and Yield Component of Fodder Maize

The purpose of this research is Effect of planting methods and plant density, on yield and yield component of fodder maize. Salinity is a major abiotic factor that limits agricultural crop production. More than 8 million hectare of world fields involved saline soils. Effect of different planting methods and plant density on yield and yield components of fodder maize studied during 2011 growth season. KSC704 variety of fodder maize planted in rural district of Abravan at south east of Mashhad. Main plots belonged to three levels of planting method (Furrow planting, ridge planting and double rows of planting on ridge). Sub plots belonged to three levels of plant density (90,000; 110,000 and 130,000 plant/ha). A split plot experiment conducted base on randomized complete design with three replications. Results showed that different planting methods had significant effect on fodder yield, ear weight, quality index and leaf area index of plants. Furrow planting with 130,000 plant density, produced the highest fodder yield by mean of 56.33 t/ha.

Effect of cowpea (Vigna unguiculata) intercropping on weed biomass and maize (Zea mays) yield

Field experiments were conducted to investigate the influence of cowpea (Vigna unguiculata) density (0, 15 or 30 plants/m2) and sowing date (15 days prior to maize sowing or simultaneously with maize), and of maize (Zea mays) planting density (7.5 or 9 plants/m2) on weed biomass and maize crop yield. Results showed that increasing the maize density from 7.5 to 9 plants/m2 reduced the weed biomass by 21.5%. Furthermore, cowpea acted as a living mulch, reducing weed biomass by up to 45.5% and 39.6% when intercropped with maize at a density of 7.5 and 9 plants/m2, respectively. Under weed-free conditions, an increase in maize density from 7.5 to 9 plants/m2 resulted in maize grain yield increasing from 8.92 to 9.40 t/ha; however, the addition of cowpea only increased the maize grain yield by about 4.2%, on average, under these conditions. By contrast, under weed-infested conditions, there was a large decrease in maize grain yield (up to 32%), but intercropping with cowpea reduced this to only a 16% decrease. Under weed-free conditions, there was no effect of sowing date on maize grain yield; however, under weed-infested conditions, yield was greater on the second sowing date. Thus, it is concluded that the planting of maize at a density of 9 plants/m2 and simultaneously intercropping with cowpea at a density of 30 plants/m2 could be an appropriate control measure for weed suppression.