Tomato leaf chlorophyll meter readings as affected by variety,nitrogen form,and nighttime nutrient solution strength

Leaf chlorophyll content is closely related to leaf nitrogen (N) content, so it is reasonable to assume that ammonium‐N (NH₄‐N): nitrate‐N (NO₃‐N) ratio in the nutrient solution used to grow tomatoes (Lycopersicon esculentum Mill.) hydroponically may affect leaf greenness, and consequently chlorophyll meter (SPAD) readings. It has also been shown that increasing nutrient solution strength (NSS) increases tomato productivity, but there are no reports regarding how NSS affects SPAD readings under greenhouse conditions. Genotype may also influence SPAD readings, and standardization for cultivar and sampling time may be needed. The objective of this study was to characterize SPAD readings for five tomato cultivars and SPAD reading response to a combination of two NSS (1X and 4X Steiner solution strength daily applied 18 days after transplanting at 7 p.m.) and two concentrations of NH₄‐N in solution (0 and 25%) in order to evaluate the potential of SPAD readings as a tomato yield predictor in greenhouse production systems. The SPAD readings were not uniform across tomato varieties tested, being consistently higher for ‘Max’ and lower for the other varieties. Initially, SPAD readings for tomato varieties used in this study were low at the vegetative stage, and increased up to 40 DAT, but subsequently decreased at 49 DAT, or the fruit set of the first and second clusters. After this time, SPAD readings showed no variation. Chlorophyll meter readings for ‘Max’ were higher in the top plant layers, but decreased in the top plant layer of the other tomato varieties. The SPAD readings were higher for plants supplied with 25% NH₄‐N than those without NH₄‐N in solution, but the use of a nighttime nutrient solution did not affect SPAD readings. None of the possible interactions among tomato variety, NH₄‐N: NO₃‐N ratio, and NSS were consistently significant.     

Influence of sulfur deficiency on chlorophyll‐meter readings of corn leaves

Sulfur (S)‐diagnostic tools are essential for rational use of S fertilizers. There is little information about the suitability of leaf greenness intensity to detect S deficiency in corn (Zea mays L.). This work evaluates, under controlled S‐stressed conditions, (1) the performance of leaf greenness intensity as an indicator of the degree of S deficiency in corn, and (2) the advantage of the upper leaves in relation to the middle leaves for S‐deficiency determination. A pot experiment using sand as growth medium was conducted in greenhouse with corn at S rates of 0, 5, 10, 20, and 40 mg kg^–1 and sufficiency of other nutrients. Measurements of aboveground biomass (AB), total nitrogen (N), and S concentrations, and chlorophyll‐meter readings (CMR) in upper and middle leaves, were performed at the growth stages of 6–7, 11–12, and 14–15 fully expanded leaves (V6‐V7, V11‐V12, and V14‐V15, respectively). Sulfur application significantly increased AB, leaf S concentration, and CMR. Significantly positive relationships were obtained between leaf S concentration and CMR. A sulfur‐sufficiency index (SSI) based on CMR measured in upper and middle leaves was significantly associated with AB (R² = 0.58 and 0.62 for the middle and upper leaves, respectively). It is concluded that under sufficiency of other nutrients and high‐S‐stressed conditions, leaf greenness intensity could be a good indicator of corn S status, although little or no advantage was found for taking CMR from the upper leaves.     

Chlorophyll meter readings,N leaf concentration and their relationship with N use efficiency in oregano

Plant-based diagnostic techniques such as chlorophyll meter (CM) readings and nitrogen (N) leaf concentration are used to determine the level of crop N nutrition, but research is limited on perennial crops and especially on aromatic and medicinal plants such as Greek oregano (Origanum vulgare spp. hirtum). The objectives of this study were to determine in a perennial crop species whether there is a relationship between the CM readings, N leaf concentration, and N use efficiency (NUE) and to use CM readings as a diagnostic tool for predicting dry matter yield in response to N fertilization. The CM readings varied across environments, growth stages, and fertilization treatments and were correlated with NUE. NUE was also affected by the environment, N fertilization, and interactions among these variables. This study provides new information about the effect of N application on CM readings, N leaf concentration, and NUE in a perennial crop such as oregano.     

玉米冠层对喷灌水量再分配影响的田间试验研究

为了确定喷灌水量通过作物冠层时的分配规律,定量评价作物冠层对喷灌水利用率的影响,该文采用水量平衡法对喷灌条件下的玉米冠层上部、棵间、茎秆下流及冠层截留水量进行了田间观测。试验结果表明,喷灌水经玉米冠层再分配后所形成的棵间和茎秆下流水量分别占冠层上部水量的45.4%和43.0%。截留水量空间分布变化较冠层上部、棵间和茎秆下流水量为大,均值为3.6 mm,变异系数Cv平均值为0.5。由相关分析知茎秆下流水量和棵间水量均随冠层上部水量的增加而线性增加,但茎秆下流水量与冠层上部水量的关系更为密切。冠层上部水量、叶面积和株高对截留量的影响较小。     

Chlorophyll meter as nitrogen management tool in malting barley

Abstract

Variable precipitation in many regions makes it difficult to predict yield goals and nitrogen (N) rates for malting grade barley (Hordeum vulgare L.). During years with below normal growing season precipitation, barley fertilized at the recommended rate often exhibits grain protein concentrations exceeding what is acceptable for malting. A study was conducted to evaluate the chlorophyll meter as a N management tool. Barley was grown under several N rates in the field. Chlorophyll meter readings and N additions were made at the Haun 4 to 5 growth stage, and grain yield and protein concentrations were evaluated at maturity. Chlorophyll meter readings, normalized as meter reading from treatment plot divided by that from a plot receiving a full N treatment at the Haun 4 to 5 growth stage, were correlated with grain yield (r²=0.67). Stands having normalized chlorophyll meter readings below 95% responded to N additions with yields equivalent to the fully fertilized stand and grain protein concentrations acceptable for malting. A N management strategy is proposed whereby 40 to 50% of the N calculated for the yield goal is applied at planting and a fully fertilized reference strip is included for each variety or soil type. At the Haun 4 to 5 growth stage, chlorophyll meter readings are taken in the reference strip and in the field. Normalized chlorophyll meter readings below 95% of the reference strip indicate a need for additional N fertilizer. This strategy will provide producers with additional time (up to a month) to evaluate growing season conditions before investing in additional crop inputs and will improve the likelihood that a barley crop acceptable for malting will be produced.     

Chlorophyll fluorescence characteristics throughout spring triticale development stages as affected by fertilization

Abstract

Little is known about the response of spring triticale (× Triticosecale Wittm.) chlorophyll fluorescence parameters (Fo – initial fluorescence intensity, Fm – maximal fluorescence, Fv/Fm – maximum quantum yield of photosystem II) to nitrogen fertilization. We investigated after-effects of basic (N₆₀P₆₀K₆₀ and N₁₂₀P₁₂₀K₁₂₀) and additional (N₃₀ and N₆₀) fertilization on chlorophyll fluorescence characteristics at four main phonological development stages of spring triticale under field conditions. Both additional nitrogen (N) rates soon after application induced short-acting stress on both basic fertilization backgrounds only in dry weather conditions. Initial fluorescence intensity exhibited direct relationship (R²=0.52) with an additional nitrogen rate only at the beginning of booting (BBCH 31) in dry 2008. The correlation of maximal fluorescence with additional nitrogen rate was significant during the whole experimental period. Maximum quantum yield of photosystem II directly correlated with both basic and additional nitrogen fertilization from flag leaf stage (BBCH 37) to completion of flowering (BBCH 69) in 2008. Initial fluorescence intensity decreased after spring triticale heading stage.     

Yield of corn as affected by potassium on a coastal plain soil

Abstract

Corn (Zea mays L.) yields were determined over a four year period on Kalmia sandy loam soil at Georgetown, Delaware. Yields were not significantly increased by the application of K fertilizer. Potassium soil test level was not significantly correlated with corn yield. Multiple extraction and leaching and changes in soil test K indicated that this soil has a K equilibrium which is reestablished sufficiently rapid to supply K to a growing corn crop.     

Relationship between chlorophyll meter readings and nitrogen in poinsettia leaves

Chlorophyll meters are used for non-destructive estimation of leaf nitrogen (N). The objective of this study was to evaluate the readings with several chlorophyll meters (SPAD-502, atLEAF, and CCM-300), different sampling sites on leaves, number of leaves used for sampling, and different types of leaf N sampling on estimation of N in leaves of potted poinsettia (Euphorbia pulcherrima) “Prestige Red.” Results showed that all meters gave readings that were correlated for N determination and also were correlated with each other. SPAD and atLEAF showed interaction between different N treatments and different sampling sites on the leaves, while CCM readings were affected by different sampling sites on the leaf. atLEAF readings showed interaction between number of leaves sampled and different N treatments. Thus, during sensor-based leaf N estimation, sampling site on leaf, number of leaves sampled, and stage of plant development should be considered to minimize error.     

Ammonium concentration in solution affects chlorophyll meter readings in tomato leaves

Abstract

Combinations of NH₄‐N:NO₃‐N usually result in higher tomato (Lycopersicon esculentum Mill.) yields than when either form of nitrogen (N) was used alone. Leaf chlorophyll content is closely related to leaf N content, but the effect of the NH₄‐N:NO₃‐N ratio on leaf greenness was not clear. The objective of this study was to determine the influence of NH₄‐N:NO₃‐N ratios on chlorophyll meter (SPAD) readings, and evaluate the meter as a N status estimator and tomato yield predictor in greenhouse production systems. Fruit yield and SPAD readings increased as the amount of NH₄‐N in solution increased up to 25%, while higher ratios of NH₄‐N resulted in a decline in both. The N concentration in tomato leaves increased as concentration of NH₄‐N in solution increased. Fruit yield increased as chlorophyll readings increased. SPAD readings, total N in leaves, fresh weight of shoots, and fruit yield all showed a quadratic response to NH₄‐N, reaching a peak at 25 or 50% of N as NH₄‐N. SPAD readings taken at the vegetative and flowering stages of growth had the highest correlation (r²=0.54) with N concentration in leaves, but this could not be used as a reliable estimate of N status and fruit yield. Lack of correspondence between high N concentration values and fruit yield indicated a detrimental effect of NH₄‐N on chlorophyll molecules or chloroplast structure. The SPAD readings, however, may be used to determine the optimum NH₄‐N concentration in solution to maximize fruit yield.     

Runoff and sorghum performance as affected by the spacing of stone lines in the semiarid Sahelian zone

Crop yields are primarily water-limited in dryland production systems in semiarid regions. This study was conducted in a catchment located in the “plateau central” of Burkina Faso to assess the impact of the space between stone lines on runoff and crop performance. The experimental design consisted of four plots in which stone lines were installed. The spacing between the lines was 100 m in the first plot, 50 m in the second, 33 m in the third, and 25 m in the last plot. The soil was a Ferric lixisol and the slope, which is characteristic of the area, was about 1–3%. Subplots placed at regular and fixed distances from the lines were used to monitor soil water content and crop yield. Runoff from all plots was measured using a water discharge recorder. It was found that 31% of rainfall was lost through runoff in plots without stone lines. The efficiency of stone lines in checking runoff and in improving soil water storage increased with reduced stone line spacing (runoff was reduced by an average of 5% on plots where the space between the lines was 33 m, but was reduced by 23% when the stone line spacing was 25 m). Soil water content decreased with increasing distance from the stone line. Sorghum (Sorghum bicolor (L.) Moench) performance was greatly affected by stone line and plant straw and grain yield were doubled in plots with stone lines compared with those of plots without stone lines. At an area of about 6 m from the stone lines (upslope), where organo-mineral sediments were collected, sorghum grain yields were 60% greater than that obtained at 19 m from stone lines. The stone line technique seems to be a sound option to mitigate water stress during dry spells.     

Root growth and mineral nutrition of corn hybrids as affected by phosphorus and lime

Abstract

The effects of triple superphosphate (TS) and liming on macronutrient accumulation and root growth of Pioneer 3072 and Cargill 505 corn hybrids were studied. Corn plants were grown up to 30 days in pots with 7 L of a dark red Latosol sandy loam (Haplortox). Lime was applied to raise base saturation to 30, 50, and 70%, in two levels of phosphorus (P) fertilization with TS (0 and 200 ppm P). There was an increase in root surface due to lime only in pots without TS, with no effects on plant growth or nutrition. Both corn hybrids responded to P fertilization, but Pioneer yielded more dry matter than Cargill. The roots of Cargill were thicker and, when in TS presence, were longer and had a larger surface than Pioneer. There was an increase in macronutrient uptake in the P fertilized pots. Pioneer required more nutrients and showed a higher efficiency in acquiring and utilizing the nutrients from the soil. A higher response of Pioneer in dry matter and nutrient acquisition was more related to the physiological efficiency than to root morphology.     

Seed composition of soybeans grown in the Harran region of Turkey as affected by row spacing and irrigation

This study was conducted to determine the effects of row spacing (RS) and irrigation (IR) on protein content, oil content, and fatty acid composition of soybeans grown in the Harran region of Turkey. Oil content of the seed varied from 20.9 to 22.3%. Oil and protein contents were both affected by year. RS and IR affected protein and oil contents significantly (P < 0.01) in both years. RS of 70 cm had the highest protein content, followed by RS of 60, 40, and 50 cm, respectively. IR every 3rd day resulted in the highest level of protein, followed by 6th, 9th, and 12th day irrigation, respectively. The correlation coefficient (r) between protein and oil content was -0.791 in 1998 and -0.721 in 1999. RS (P < 0.01) and IR (P < 0.01) influenced oleic and linoleic acid contents significantly. Interactions of RS and IR were also found to be significant (P < 0.05) for the oleic and linoleic acid contents of soybeans.     

Chlorophyll meter as a tool for forecasting wheat nitrogen requirements after application of herbicides

Because limited information is available about the validated use of a chlorophyll meter for predicting nitrogen requirements for optimum growth and yield of wheat after application of herbicides, field experiments were carried out in the winter seasons of 2011/2012 and 2012/2013 under different weed and N fertilization treatments. Five weeded treatments, application of herbicides 25 days after sowing (DAS), hand pulling once at 55 DAS and a weedy check were combined with four N application rates. Weeds were completely absent in the non-fertilized plots, either with metribuzin or hand pulling as well as in isoproturon-treated plots fertilized with 190 or 285 kg N ha^?1. The grain yield was similar in the treatments of isoproturon × 190 kg N ha^?1, isoproturon + diflufenican × conditional N treatment (113.9) or 190 kg N ha^?1, hand pulling × conditional N treatment (104.8) or 285 kg N ha^?1 and metribuzin × 190 kg N ha^?1. Under weeded practices, conditional N treatment recorded the maximum nitrogen use efficiency and almost equaled the grain protein content of the 190 kg N ha^?1 application rate. N application based on SPAD readings saved about 40.0% and 44.8% N with isoproturon + diflufenican or hand pulling, respectively, compared to the recommended rate (190 kg N ha^?1) without noticeable yield loss.     

The nitrogen content of corn grain as affected by hybrid,population, and location

Abstract

Samples were taken from 9 of the 20 major experiments which comprised the Illinois commercial corn (Zea mays L.) performance trial and evaluated for grain yield, percent grain N, and grain N yield.

The mean percent N in the grain was 1.54%, with 91.8% of the samples between 1.34 to 1.74%. Although location and plant population affected the mean values, the range of values about the mean was relatively unaffected. Grain N yield was more closely correlated with grain yield than with percent grain N.     

Physico-mechanical properties and yield of silage corn as affected by soil compaction and tillage methods

Experimental investigations were conducted over three years to test the hypothesis that soil compaction affects the physical and mechanical properties of corn ears and corn cobs. Field experiments were made on sub-drained clay and sandy loam soils at Macdonald College Farm in Quebec Province of Canada. The mechanical properties of corn ears and corn cobs were determined from quasi-static force-deformation analysis performed with a universal Instron testing machine.

The results showed that soil compaction treatments did not significantly influence corn cob elastic modulus and strength in simple bending nor in radial compression. Cob moisture content did not significantly change as a result of the application of various traffic treatments. However, corn cob diameter and pith diameter were both significantly affected by soil compaction.

Corn ear moisture content and bending strength were not significantly affected by soil compaction. However, corn ear yield in all three years was found to be dependent on the amount of soil compaction applied.

Also studied were the effects of various tillage methods in ameliorating the deleterious effects of soil compaction on crop yield and crop quality. It is concluded that a judicious choice of tillage machinery system can minimize the reductions in ear yield due to soil compaction.     

玉米秸秆应用和腐化对钙质苏打土改良的影响: 实验室试验研究

A laboratory lysimeter experiment was conducted to investigate the effects of forage corn (Zea mays L.) stalk application on the CO₂ concentration in soil air and calcareous sodic soil reclamation. The experimental treatments tested were soil exchangeable sodium percentage (ESP) levels of 1, 11, and 19, added corn stalk contents of 0 to 36 g kg^-1, and incubation durations of 30 and 60 days. The experimental results indicated that corn stalk application and incubation significantly increased CO₂ partial pressure in soil profile and lowered pH value in soil solution, subsequently increased native CaCO₃ mineral dissolution and electrolyte concentration of soil solution, and finally significantly contributed to reduction on soil sodicity level. The reclamation effciency of calcareous sodic soils increased with the added corn stalk. When corn stalks were added at the rates of 22 and 34 g kg^-1 into the soil with initial ESP of 19, its ESP value was decreased by 56% and 78%, respectively, after incubation of 60 days and the leaching of 6.5 pore volumes (about 48 L of percolation water) with distilled water. Therefore, crop stalk application and incubation could be used as a choice to reclaim moderate calcareous sodic soils or as a supplement of phytoremediation to improve reclamation effciency.     

Artificial neural networks to estimate the productivity of soybeans and corn by chlorophyll readings

Crop productivity prediction techniques assist with adjusting for potential agronomic problems during the growing season. Several authors have reported that there is a correlation between leaf chlorophyll (Chl) content and yield. This study developed independent artificial neural network (ANN) models for soybean and corn in order to predict the crops' productive potentials using their respective yields and leaf Chl content data, measured at three stages of plant development. The ANN was deemed ready for testing through verification of the mean squared error and the number of epochs while training the neural network. While the model obtained when Chl was measured in the V6 stage of development explained more than 50% of the productivity data in corn, the models obtained for soybean did not explain more than 10% of the observed data. Attempts to improve the model through changes of the architecture of the neural network did not show any improvement in model.     

Soil microbial metabolism and nutrient status in a Mediterranean area as affected by plant cover

The Mediterranean area of Southern Italy is characterized by different natural plant covers that mainly reflect different successional stages (i.e. low maquis, high maquis, Quercus ilex wood) and managed areas with introduced plant species (such as Pinus species). Soil properties could be affected by plant cover types as well as by plant species. Our objective was to determine the relationships of plant cover types and plant species with the chemical and biological characteristics of the soil. In four neighbouring areas with different plant cover types (low maquis, pure high maquis, high maquis with pines and pinewood, with pines planted by foresters in both cases), soil samples were collected under different plant species in order to evaluate the effect of plant cover types and plant species on soil properties. Soil samples were analyzed for nutrient content, microbial biomass, soil potential respiration and enzymatic activity (phosphatase, arylsulphatase, β-glucosidase and hydrolase activities) as well as for pH, water holding capacity (WHC) and cation exchange capacity (CEC). Application of cluster analysis and principal component analysis to the data revealed that the plant cover type was the key factor influencing soil properties more than plant species. In fact, the largest differences were observed between pure high maquis soils and all other soils, with pure high maquis soils generally showing the highest values of WHC, CEC, nutrient content, organic and microbial C, soil respiration, phosphatase, arylsulphatase and β-glucosidase activities. The significantly lower values of these variables in the low maquis relative to the pure high maquis probably reflect the effect of ecological succession on soil. The high maquis with pine, differing from the pure high maquis only for the presence or absence of pine, showed values of soil physical, chemical and biological characteristics similar to those found in the low maquis, thus suggesting that the presence of pine retards soil development.