Jerry W. Maranville

Photosynthesis Light Sensor and Meter

An improved light sensor with a spectral response based on photon absorption between 400 and 700 nm was developed for both field and environmental chamber use. The indicated sensor response was selected because it approximates the photosynthetic response of plants for which data are available. A silicon photo cell with high response in the visible range was used as a sensor. The spectral response was controlled by use of a Kodak Gelatin Wratten Filter. A visible bandpass interference filter produced a sharp cutoff at 700 nm. Heat—absorbing glass eliminated transmission beyond 1,000 nm, and a diffusing plastic and filters were mounted in a miniaturized cosine—corrected head that was fitted with a collimating system to eliminate spectral shifts which arise when light enters the interference filter at oblique angles. Error calculations indicate that under sun—and—sky radiation and various artificial light sources the errors are smaller than those associated with available standard calibration lamps. The device also includes a battery—operated meter circuit suitable for making measurements over a wide range of intensities.

Effects of species of VA-mycorrhizal fungi on growth and mineral uptake of sorghum at different temperatures

Sorghum [Sorghum bicolor (L.) Moench] plants were grown in growth chambers at 20, 25 and 30°C in a low P Typic Argiudoll (3.65 µg P g−1 soil, pH 8.3) inoculated with Glomus fasciculatum, Glomus intraradices, and Glomus macrocarpum to determine effects of vesicular-arbuscular mycorrhizal fungi (VAMF) species on plant growth and mineral nutrient uptake. Sorghum root colonization by VAMF and plant responses to Glomus species were temperature dependent. G. macrocarpum colonized sorghum roots best and enhanced plant growth and mineral uptake considerably more than the other VAMF species, especially at 30°C. G. fasciculatum enhanced shoot growth at 20 and 25°C, and mineral uptake only at 20°C. G. intraradices depressed shoot growth and mineral uptake at 30°C. G. macrocarpum enhanced shoot P, K, and Zn at all temperatures, and Fe at 25 and 30°C above that which could be accounted for by increased biomass. Sorghum plant growth responses to colonization by VAMF species may need to be evaluated at different temperatures to optimize beneficial effects.

Interactive effects of water and nitrogen stresses on nitrogen utilization efficiency, leaf water status and yield of corn genotypes

Abstract Information on the combined effects of N and water stresses on corn (Zea mays L.) is of importance for selecting nitrogen efficient and drought tolerant genotypes. Greenhouse and field experiments were conducted to determine the interactive effects of N and water stresses on N utilization efficiency (NUE), leaf water status and yield of diverse corn genotypes. Three genotypes which normally rank differently for NUE in the field, were grown to the 9‐leaf stage in the greenhouse with four N rates of 0, 30, 60, and 90 mg/kg and two water regimes (stressed for 8‐d, and unstressed). In the field experiment, four genotypes with different NUE history, were grown with N rates of 0, 60, 120, and 180 kg/ha, and water regimes of irrigated and dryland. Maximum grain yield was obtained at different N rates for different genotypes and for different water regimes. The genotypes differed significantly in NUE as expected, but also for water use efficiency (WUE) in both experiments. Nitrogen x water regime interac...

NITROGEN FERTILIZER RESPONSE AND USE EFFICIENCY FOR THREE CEREAL CROPS IN NIGER

Nitrogen (N) is one of the most limiting nutrients for cereal production in many areas of west Africa such as Niger. One of the strategies to improve yields is to choose crops with high N use efficiency (NUE) that can produce economic yield under limited water supply. Little information is available on comparative performance of pearl millet [Pennisetum glaucun (L.) R. Br.], sorghum [Sorghum bicolor (L.) Moench], and maize (Zea mays L.) for their NUE. A field experiment was conducted to evaluate several components of NUE for the three crop species on a Psammentic Paleustalf sand at two locations in 1997 and three locations in the 1998 rainy seasons in Niger. Nitrogen use efficiency components were calculated as incremental increases in yield per applied N or per plant N. Leaf area index and leaf chlorophyll were determined as concomitant data. Among the three cereals, sorghum and millet had greater responses to N (kg grain kg−1 N) than maize. Nitrogen use efficiency differed widely among species. Partial factor productivity (kg grain kg−1 N applied) was higher in sorghum and pearl millet than maize over three sites in two years and declined with increasing N levels. Agronomic NUE (Δ grain weight kg−1 N applied) was also higher in sorghum compared to pearl millet and maize over all N rates. Nitrogen recovery efficiency (Δ grain weight kg−1 N applied) was higher in sorghum followed by millet and lowest in maize. Marginally lower NUE for biomass production in pearl millet was associated with higher biomass yield in non-fertilized treatments. The ability of pearl millet to extract N from nutrient degraded sandy soils and its better drought tolerance is the primary reason for its adaptation to the Sahel where it produces a moderate although reliable grain yield. Although pearl millet tended to have better performance where frequent drought was prevalent, sorghum had higher yields than pearl millet under improved N management and thus can significantly contribute to enhancing food production in areas where good management is practiced. This study also indicated that N deficiency could be detected using a SPAD chlorophyll meter early enough to apply additional N for achieving target yield levels.

Benefit and cost analysis and phosphorus efficiency of VA mycorrhizal fungi colonizations with sorghum ( Sorghum bicolor ) genotypes grown at varied phosphorus levels

Sorghum [Sorghum bicolor (L.) Moench] was grown in a greenhouse in a low P (3.6 mg kg-1) soil (Typic Argiudolls) inoculated with the vesicular-arbuscular mycorrhizal fungi (VMAF) Glomus fasciculatum and P added at 0, 12.5, 25.0, and 37.5 mg kg-1 soil to determine the effects of VAMF-root associations on plant growth, benefit and cost analysis, and P efficiency (dry matter produced/unit P absorbed). Root colonization with VAMF and shoot growth enhancements decreased with increased soil P applications. Mycorrhizal plants were less P efficient than nonmycorrhizal plants. Shoot dry matter differences between mycorrhizal and nonmycorrhizal plants were considered the benefit derived by plants from VAMF-root associations. Shoot dry matter differences between mycorrhizal and nonmycorrhizal plants with similar P concentrations were considered the costs paid by plants for VAMF-root associations. Values of benefit and cost analysis for VAMF-root associations were highest when soil P was lowest and decreased with increasing P applications. Genotypic differences for calculated costs were pronounced, but not benefits. Benefit and cost analysis.may be helpful to evaluate host plant genotypes and VAMF species to optimize efficiencies of VAMF symbiosis in different soil environments.

Physiological adaptations for nitrogen use efficiency in sorghum

Known high nitrogen utilization efficiency (NUE1, biomass per unit plant N) China lines of sorghum, China 17 and San Chi San, were compared with relatively low NUE1 U.S. lines, CK60 and Tx623, for both their physiological and biochemical adaptations to tolerate an imposed N stress in the greenhouse. Assimilation efficiency indices (ACi) were significantly greater for the China lines than the U.S. lines at both low and high soil nitrogen levels by about two-fold. Chlorophyll levels in leaves of high NUE1 lines were lower at both soil N treatments. Immunoblots of leaf extracts of sorghum subjected to N stress indicated reduced levels of both phosphoenolpyruvate carboxylase (PEPcase) and ribulose 1,5-bisphosphate carboxylase (Rubisco) while NADP-malic enzyme levels, in general, appear not to be affected. However, NUE1 China line, China 17, retained a significantly greater PEPcase activity than the less-NUE1 U.S. lines, and also the NUE1 China line San Chi San, when grown under N stress conditions. This suggests that PEPcase and enzymes associated with phosphoenolpyruvate synthesis, perhaps, are significant factors in maintaining relatively high photosynthesis under N stress. Carbon isotope ratios of leaves from sorghum genotypes, as indicated by δ13C values, became less negative when sorghum plants were grown under N stress, but a genotypic variation either at a low or high N was not observed.

Carbon dioxide assimilation efficiency of maize leaves under nitrogen stress at different stages of plant development

Abstract Sub‐optimal nitrogen (N) affects the N‐rich carbon dioxide (CO2) assimilation enzymes which can limit maize (Zea mays) production. The status of the carboxylation system is closely correlated to the Assimilation Efficiency Index (AEI) which is the initial slope of the CO2 assimilation rate versus intercellular leaf CO2 concentrations. Experiments were undertaken to ascertain the effect of soil N nutrition on the AEI, determine genotypic variability for AEI under N‐deficiency, determine how leaf and plant development affect treatment differences, and examine correlations between the AEI and plant development. Studies were conducted in the field and greenhouse on five maize genotypes on leaves of different ages at three stages of plant development. Field studies were conducted on a fine, silty mixed, mesic cumulic Hapludoll (1.2 g N kg‐1), and high and low N treatments were imposed in the greenhouse. Quantum yield of emerging and mature leaves was determined. Results indicated that emerging and ful...

Comparison of nitrogen use efficiency of a newly developed sorghum hybrid and two improved cultivars in the Sahel of West Africa

In Sahelian areas such as Niger, West Africa, grain sorghum [Sorghum bicolor (L.) Moench] is grown under conditions of low soil nitrogen (N) availability on degraded land with little or no fertilizer N application. Nitrogen use efficiency (grain weight per unit of N supplied from soil and/or fertilizer) is reduced due to poor crop cultural practices, lack of appropriate cultivar, sub-optimal yields and N losses or deficiency of other nutrients. However, little is known about traits that contribute to differences in land races and hybrids for their performances and the adaptive mechanism of N utilization on sandy soils in a high risk environment. A three-year study was conducted to examine the N use efficiency of three cultivars: hybrid NAD-1, and improved lines Sepan82 and IRAT 204 at different N levels to identify their specific characteristics and appropriate management systems to enhance productivity. Three cultivars differed in N extraction capacity from soil indigenous N, where external N was not applied. At 90 kg ha−1 N and above, NAD-1 was more efficient in biomass production and grain yield than the two improved lines which were selected from land races, but biomass yields were similar. NAD-1 had higher N use efficiency as measured by partial factor productivity (increase in yield per unit applied N) compared to Sepan82 and IRAT 204. However, differences in agronomic efficiency, N recovery efficiency, physiological efficiency and biomass production efficiency did not differ significantly among cultivars. Harvest index and improved N uptake in NAD-1 were associated with high grain yield compared to Sepon82 or IRAT 204. Chlorophyll content of leaves estimated by a chlorophyll meter generally determined leaf N status up to 180 kg ha−1 applied N. This may have potential as a management tool since optimum N application in the degraded Sahelian soils of West Africa and use of superior cultivars such as hybrids are extremely important in determining potential productivity.

Seedling vigor and nitrogen use efficiency of Moroccan wheat as influenced by level of soil nitrogen

Abstract One of the characteristics that can help wheat (Triticum aestivum L.) plants escape late season drought in the semiarid areas of Morocco is early stand establishment and adequate vigor. Little is known about the effect of nitrogen (N) on early seedling vigor in wheat. The objective of this study was to determine how N supply affects early root and shoot growth, N partitioning between the two parts and N use efficiency of seedlings. To reach this objective, three spring wheat cultivars were grown in pots in a growth chamber under N conditions which were low, adequate and high. Data showed that optimum N rates increased shoot and root growth but high N concentrations reduced their dry matter accumulation and inhibited root elongation. The cultivars tested behaved differently. ‘Nesma’, an older cultivar, produced 60% more dry matter and accumulated 93% more N in the shoot and root than the newer cultivars ‘Merchouch 8’ and ‘Saada’. Because of its high N uptake, ‘Nesma’ probably reduced soil N concen...

Evaluation of agronomic and energy traits of Wray sweet sorghum and the N39 × Wray hybrid

Abstract Recent emphasis on energy problems has stimulated efforts to identify crops capable of producing high yields of biomass that can be converted into ethanol. The sorghum [ Sorghum bicolor (L.) Moench] crop includes cultivars and hybrids that vary widely in the relative amounts of grain and stalks produced, and also in the sugar content of the stalks. N39 × Wray, a relatively sweet hybrid with good grain potential, and Wray, a cultivar with sweet stalks, were compared for their grain and sugar yields, alcohol production potential, and other related characters. The hybrid produced heavier seeds, more seeds per head, and more heads per ha than the Wray. This resulted in a grain yield of 6630 kg/ha, about 3.4 times that of Wray. Wray produced about 10% more biomass with the stalk sugars accounting for about 80% of the total alcohol potential as compared to 45% for the hybrid. The total alcohol production potential (stalk plus grain) was 1.11 times as great for the hybrid as for Wray.