Farmers’ adoption of maize (Zea mays L.) hybrids and the persistence of landraces in Southwest China: implications for policy and breeding

This paper examines changes in the distribution of maize hybrids and landraces in the mountainous areas of southwest China over 1998–2008, farmers’ reasons for cultivar adoption and the implications for national policies in relation to seed production and breeding, based on baseline data and a survey conducted in Guangxi, Yunnan and Guizhou. The study traced the dynamic changes in the adoption of hybrids and landraces in farmers’ fields, explored how individual farmer’s choices can influence local landrace distribution, and investigated the space for conducive policy and innovative action for on-farm conservation of maize genetic resources. The research showed that although there is strong farmers’ interest in accessing modern maize hybrids, farmers also express strong reasons for maintaining at least some of the landraces that satisfy local agronomic context and social preferences. Farmers recognized that hybrids have a number of advantages but they also indicated some disadvantages of the current available hybrids e.g. with respect to seed quality, local adaptability, taste and cost of seeds, but also lack of information on the performances of the new hybrids. Based on farmers’ reasoning and experiences, the requirements have been identified for improving yield combined with local preferences (agronomic, cultural and socio-economic). The paper concludes by identifying options for how China might seek to develop resilient seed systems for smallholder farmers in poor areas, under changing climatical conditions and volatile markets. Participatory Plant Breeding is among the options considered for bringing farmers’ needs into conservation and breeding strategies for improving local adaptation.     

Influence of Azospirillum inoculation and nitrogen supply on grain yield,and carbon‐ and nitrogen‐assimilating enzymes in maize

Nitrogen (N) supply increased yield, leaf % N at 10 days after silking (DAS) and at harvesting, the contents of ribulose‐1,5‐bisphosphate carboxylase (RUBISCO) and soluble protein, and the activities of phosphoenolpyruvate carboxylase (PEPC), and ferredoxin‐glutamate synthase (Fd‐GOGAT), but not of glutamine synthetase (GS) for six tropical maize (Zea mays L) cultivars. Compared to plants fertilized with 10 kg N/ha, plants inoculated with a mixture of Azospirillum sp. (strains Sp 82, Sp 242, and Sp Eng‐501) had increased grain % protein, and leaf % N at 10 DAS and at harvest, but not grain yield. Compared to plants fertilized with either 60 or 180 kg N/ha, Azospirillum‐inoculated plants yielded significantly less, and except for GS activity, which was not influenced by N supply, had lower values for leaf % N at 10 DAS and at harvest, for contents of soluble protein and RUBISCO, and for the activities of PEPC and Fd‐GOGAT. Yield was positively correlated to leaf % N both at 10 DAS and at harvest, to the contents of soluble protein and RUBISCO, and to the activities of PEPC and Fd‐GOGAT, but not of GS, when RUBISCO contents and enzyme activities were calculated per g fresh weight/min. However, when enzyme contents and enzyme activities were expressed per mg soluble protein/min, yield was correlated positively to RUBISCO and PEPC, but negatively to GS. These results give support to the hypothesis that RUBISCO, Fd‐GOGAT, and PEPC may be used as biochemical markers for the development of genotypes with enhanced photosynthetic capacity and yield potential.     

The effect of gypsum and other salts on the growth of narrow‐leafed lupins

Abstract

Glasshouse experiments were conducted to establish the cause of poor lupin growth in the presence of gypsum in field trials which had been conducted in Western Australia. In the first experiment, Bradyrhizobium‐inoculated lupins were grown in nutrient solutions with varying concentrations (1, 3, 5, and 10 mM) of calcium (Ca) and sulfate (SO₄) added as either CaSO₄, K₂SO₄, or CaCl₂ to establish whether gypsum caused Ca or SO₄ toxicity to the plants. Although a general decrease in lupin plant growth was observed as the concentration of each salt increased, there was no evidence that either Ca or SO₄ directly caused toxicity to the plants. Two soil experiments were therefore conducted to investigate lupin growth responses to the salts in a soil environment. The first soil experiment was conducted in a yellow earth— the same soil in which lupins had been adversely affected by gypsum in the field. The second soil experiment was conducted in the topsoil of a siliceous sand. Basal nutrients and different rates of CaSO₄, K₂SO₄, and CaCl₂ were added so that similar amounts of Ca and SO₄ were present for each treatment at a given application rate. In both soils, lupin growth generally decreased as the application rate of treatments increased, although the magnitude of the decrease in growth was higher in the yellow earth than the siliceous sand. The strongest correlation between lupin growth and a soil solution chemical property was a log‐linear relationship between the shoot or root dry weight and the electrical conductivity (EC) of the soil solution. Plant nutrition was affected by different treatments, particularly with respect to nutrient balances. It is suggested that a high ionic strength in the soil, which results when gypsum is applied in the field, may contribute to the lupin yield decline. Possible reasons for the effect are discussed.     

Effects of a ‘one film for 2 years’ system on the grain yield,water use efficiency and cost-benefit balance in dryland spring maize (Zea mays L.) on the Loess Plateau,China

‘One film for 2 years’ (PM2) has been proposed as a practice to control the residual film pollution; however, its effects on grain-yield, water-use-efficiency and cost-benefit balance in dryland spring maize production have still not been systematically explored. In this study, we compared the performance of PM2 with the annual film replacement treatment (PM1) and no mulch treatment (CK) on the Loess Plateau in 2015–2016. Our results indicated the following: (1) PM2 was effective at improving the topsoil moisture (0–20 cm) at sowing time and at seedling stage, but there was no significant influence on soil water storage, seasonal average soil moisture or evapotranspiration; (2) PM2 induced significantly higher cumulative soil temperatures compared to CK, and there was no significant difference between PM2 and PM1; (3) no significant differences were identified in grain-yield and water-use-efficiency between PM1 and PM2, and compared to CK, they improved by 16.3% and 15.5%, respectively; (4) because of lower cost of plastic film, tillage, film laying and remove in PM2, economic profits improved by 21% and 70% compared to PM1 and CK. This research suggested that PM2 was effective at alleviating the spring drought and was beneficial in reducing poverty traps in dryland.     

Interactions of oxygen‐nitrogen‐salinity stresses on plant growth and mineral content of sunflower (Helianthus annuus L.) in sand culture

Reports relating the separate and combined influences of soil aeration, nitrogen and saline stresses on the germination, growth and ion accumulation in sunflowers are lacking in the literature. The sunflowers of this report were grown in sand culture in the greenhouse. Separate and combined treatments of two levels of aeration, three levels of nitrogen and three levels of NaCl were applied to plants which were harvested at 40 and 56 days. Seed germination was excellent in all treatments. Plant height and dry weight decreased with each type of stress. Low oxygen (0.20 μg O₂ cm^‐2 min^‐1) and nitrogen (10 ppm) combined with 70 meq/1 NaCl caused the greatest reduction of plant growth. Leaf number was reduced by low nitrogen and excess salt. Low oxygen reduced the accumulation of K, Ca and Mg and increased the Na and N‐NO₃ content of sunflower leaves. Potassium to sodium ratios in plant on sunflower growth could be partially ameliorated with the tissue were decreased by greater EC values of the nutrient solution and low soil ODR. The adverse effects of salt and oxygen stresses addition of nitrogen. Ion accumulation was an earlier indicator of plant stress than plant growth and both parameters provided excellent methods for assessing plant tolerance to soil aeration, nitrogen and saline stresses.     

Evaluation of urea ammonium polyphosphate (UAPP) I. Effectiveness of banded and seed‐placed UAPP on irrigated corn (Zea mays L.)

Abstract

Field trials were established on an irrigated loamy sand using corn as a test crop. Row fertilizer was placed with the seed (seed‐placed) or in the conventional side placement position (side‐placed). The side‐placed treatments consisted of two carriers of UAPP (28–28–0 and 36–18–0), diammonium phosphate (DAP, 18–46–0) plus ammonium nitrate (AN, 33–0–0), and a control treatment. Two rates of application were used for each carrier. Seed‐placed treatments consisted of two carriers of UAPP (28–28–0 and 36–18–0), concentrated superphosphate (CSP, 0–45–0) plus AN, CSP, AN, and a control treatment. Two rates of application were used for each carrier, except AN, which was used at three rates.

High rates of side‐placed UAPP delayed emergence of corn and lowered the final population. Early season N concentration in corn seedlings was not affected by rate or carrier of side‐placed N. Early season P concentration in the corn seedlings was greater for AN + DAP than UAPP treatments at all rates of P, presumably due to toxic accumulation of free NH₃ in the UAPP band. High rates of side‐placed UAPP also reduced the yield of corn.

High rates of seed‐placed AN + CSP and UAPP reduced the germination of corn. However, low rates of UAPP also reduced germination, whereas low rates of AN + CSP did not affect germination. Since UAPP has a lower salt index than AN + CSP, the “salt effect”; of low rates of UAPP does not explain its effect on germination and emergence. The deleterious effects of UAPP were due apparently to either NH₃ or NO₂‐N toxicity.     

Effect of nitrogen and sulphur fertilizers and seed inoculation with rhizobium phaseoli on the nitrogen‐sulphur relationships of bean (phaseolus vulgaris L.)

A greenhouse experiment with beans (Phaseolus vulgaris L.) was performed in order to investigate the effect of nitrogen and sulphur application and seed inoculation on the yield, leaf area, distribution of different nitrogen and sulphur fractions and N/S ratio in shoot, fruit and root.

Inoculation of plants together with nitrogen or sulphur application produces an increase in the concentration of total nitrogen and a decrease in the accumulation of nitrate‐nitrogen and sulphate‐sulphur in shoot, fruit and root. Leaf area increased more with nitrogen than with sulphur application while the highest amounts of fruit dry matter were obtained with sulphur application.

N: S ratios obtained were different according to the part of the plant tested. Sulphur fertilization decreased the N: S ratios in shoot, fruit and root. The data obtained indicate that and adequate N: S ratio can insure maximum production of yield.     

Transfer of rubidium‐86 (potassium) from deeply‐rooted alfalfa (Medicago sativa L.) to associated,shallow‐rooted maize (Zea mays L.) or grain sorghum (Sorghum vulgare pers.).

Circumstantial evidence exists for non‐N‐mineral element transfer in legume‐grass associations. Three experiments were conducted in an effort to directly demonstrate transfer of a non‐N‐mineral element in alfalfa (Medicago sativa L.)‐maize (Zea mays L.) and alfalfa‐grain sorghum (Sorghum vulgare Pers.) associations in two rooting media. Associations were established in double‐tube apparatus so that a single alfalfa plant was rooted in media of top‐ and bottom‐tubes, while an associated grass plant was rooted exclusively in the top‐tube (Intact treatment). Severed treatments (the control) were identical to the Intact treatments except the alfalfa roots in an air gap between the top‐and bottom‐tubes were excised.

⁸⁶Rb was dispensed onto the medium of bottom tubes with movement of the radioisotope determined by analyzing the legume and grass tissues over time. ⁸⁶Rb was detected in: i) soil‐grown maize associated with alfalfa within a 40‐day treatment period; ii) sand‐grown maize associated with alfalfa within 20 days after treatment and iii) sand‐grown sorghum associated with alfalfa within 10 days. Detection of ⁸⁶Rb in grass plants associated with alfalfa demonstrated that transfer of this potassium analog can occur via the root systems of legume‐grass associations.     

Effect of nitrogen on the growth and photo‐synthetic activity of salt‐stressed barley

Pot experiments were conducted in the greenhouse to study the effect of nitrogen (N) nutrition on photosynthesis and water relations of barley plants under salinity conditions. Nitrogen decreased the sodium (Na) content and increased the potassium (K) content in shoots. The net photosynthetic rate of leaves increased significantly with added N increasing from 0 to 100 mg N/kg soil. The activity of ribulose 1,5 bisphosphate carboxylase (RuBPC_ase) in leaves of high‐salt plants was lower, and in leaves of the low‐salt plants higher than that in control plants. The photosynthetic rate was reduced by sodium chloride (NaCl) and was significantly correlated with total soluble protein per unit leaf area. At each N level, stomatal conductance in leaves was reduced considerably by salt. Proline content of leaves increased with increasing N level. It was higher in leaves of salt‐treated plants than in those of control plants. The osmotic potential of leaves decreased with increasing N applied, and the turgor pressure of high N plants remained higher under salt treatment condition.     

Host–pathogen interaction of maize (Zea mays L.) and Aspergillus niger as influenced by arbuscular mycorrhizal fungi (Glomus deserticola)

This study was carried out to investigate the interaction of maize and Aspergillus niger as influenced by arbuscular mycorrhizal fungi (AMF). Three quality protein maize (QPM) genotypes (ILE1-OB, ART-98-SW5-OB and ART-98-SW6-OB) and two market accessions (Ilishan and Shagamu) were evaluated in a pot experiment conducted under natural environment conditions at the Research and Teaching Farm of Babcock University, Ogun State, Nigeria. AMF (Glomus deserticola) in mixtures of soil and root fragments was inoculated at the rate of 15 g per plant, while maize was artificially infected with A. niger (15 cfu ml^?1) in each designated pots. The coefficient of emergence (COV), percentage emergence (% E) and disease severity were determined using standard methods. Generally, plants treated with AMF only produced the highest cumulative cob yield (18 g), followed by plants treated with AMF and A. niger (15 g) and then control (12 g), while the least was recorded for only A. niger-treated plants (4 g).     

Different Forms of Potassium and Their Contributions toward Potassium Uptake under Long-Term Maize (Zea mays L.)–Wheat (Triticum aestivum L.)–Cowpea (Vigna unguiculata L.) Rotation on an Inceptisol

In a long-term fertilizer experiment at the Indian Agricultural Research Institute, New Delhi, with maize, wheat, and cowpea, various forms of potassium (K) and their contribution toward K uptake were found to be affected by fertilizer use and intensive cropping. The treatments included for the study were a control, 100% nitrogen (N), 100% N–phosphorus (P), 50% NPK, 100% NPK, 100% NPK + farmyard manure (FYM at 15 t ha^?1 to maize only), and 150% NPK. The concentration of nonexchangeable K was greatest, followed by exchangeable K and water-soluble K. The study revealed no significant change in water-soluble K concentration in surface soil compared to N, NP, and control, indicating existence of an equilibrium between different K forms. Application of 100% NPK significantly increased water-soluble K concentration in surface soil compared to N, NP, and control treatments after maize, wheat, and cowpea. Application of NPK + FYM and 150% NPK resulted in greater quantities of all the K forms as compared to other treatments. Among the three forms, water-soluble K contributed predominantly to K uptake by maize and wheat; however, nonexchangeable K contributed significantly to K uptake by cowpea.     

Time of availability influences mixed‐nitrogen‐induced increases in growth and yield of wheat 1

Previous studies have indicated that under hydroponic conditions, spring wheat (Triticum aestivum) plants produce higher grain yields, more tillers, and increased dry matter when continuously supplied with mixtures of NO₃ and NH₄ than when supplied with only NO₃. The objective of this study was to determine if mixed N needs to be available before or after flowering, or continuously, in order to elicit increases in growth and yield of wheat. During vegetative development, plants of the cultivar ‘Marshal’ were grown in one of two nutrient solutions containing either a 100/0 or 50/50 mixture of NO₃ to NH₄ and, after flowering, half the plants were switched to the other solution. At physiological maturity, plants were harvested, separated into leaves, stems, roots, and grain and the dry matter and N concentration of each part determined. Yield components and the number of productive tillers were also determined. Availability of mixed N at either growth stage increased grain yield over plants receiving continuous NO₃, but the increase was twice as large when the mixture was present during vegetative growth. When the N mixture was available only during vegetative growth the yield increase was similar to that obtained with continuous mixed N. The yield increases obtained with mixed N were the result of enhanced tillering and the production of more total biomass. Although plants receiving a mixed N treatment accumulated more total N than those grown solely with NO₃, the greatest increase occurred when mixed N was available during vegetative growth. Because availability of mixed N after flowering increased the N concentration over all NO₃ and pre‐flowering mixed N plants, it appears that the additional N accumulation from mixed N needs to be coupled with tiller development in order to enhance grain yields. These results confirm that mixed N nutrition increases yield of wheat and indicate that the most critical growth stage to supply the N mixture to the plant is during vegetative growth.     

Dry matter and nitrogen accumulations in determinate soybean grown on low‐nitrogen soils of the southeastern United States

Abstract

Reliable assessments of erosion potential, N fertilization need, and nitrogen (N) non‐point pollution potential for soybean [Glycine max (L.) Merr.] cropping systems require accurate estimates of soybean dry matter and N accumulations. The objective of this field study was to determine dry matter and N accumulation in soybean during the growing season and at harvest in samples large enough to reduce sample variation and increase the confidence in measured values. A split‐plot design was used with cultivar (Braxton, Coker 338, and Davis) as the main plot treatment and sampling date as the split‐plot treatment. Each split‐plot contained eight rows 4.6 m in length on 0.75 m spacing. The seed were sown in a Norfolk loamy sand (fine‐loamy, siliceous, thermic, Typic Paleudult) on May 18 at the rate of 33 seeds/m. Water was applied by use of an overhead irrigation gun. Plant samples were collected from 20 m² of the six center rows on 89, 115, and 138 days after planting as well as at seed harvest. Fallen plant material (crop litter) was collected from each plot at each sampling date. Itact plant samples, crop litter, and soil samples were analyzed for total Kjeldahl N. The mean seed yield was 2.01 Mg/ha; the mean maximum dry matter accumulation for intact shoots plus crop litter was 10.2 Mg/ha, and the coefficients of variation were <10%. The actual harvest index (seed yield/total dry matter accumulation) ranged from 0.19 to 0.28, and the mean maximum N accumulation was 293 kg/ha. These accumulations are greater than those reported for indeterminate soybean grown on high‐N soils in the midwestern United States, and they clearly show that determinate soybean grown in the southeastern United States accumulate substantial amounts of dry matter and N.     

Effect of different safflower (Carthamus tinctorius L.)–bean (Phaseolus vulgaris L.) intercropping patterns on growth and yield under weedy and weed-free conditions

Two field experiments were carried out over two consecutive years (2010–2011) in the research field of the College of Agriculture, Shiraz University, Fars Province, southern Iran. The study was a factorial experiment based on a randomized complete block design with three replications: the first factor was the ratio of safflower (Carthamus tinctorius L. Pi cv.) to bean (Phaseolus vulgaris L. Saiad cv.) at five levels (safflower and bean sole cropping, and intercropping of safflower and bean at ratios of 1:3, 2:2 and 3:1); and the second factor was weed management at two levels: weed-free (complete weed control) and weedy (no weed control). The results showed that an intercropping system was the most appropriate method for decreasing the adverse effect of weeds on the performance of both crops. Intercropping was more suitable for weedy than weed-free conditions. According to the land equivalent ratio (LER) value, if the main crop was bean, the best intercropping treatment was one row of safflower and six rows of bean (S₁B₃) under both weedy and weed-free conditions. By contrast, if the main crop was safflower, the best treatment under weedy conditions was S₁B₃, whereas under weed-free conditions the best treatment was two rows of safflower and four rows of bean (S₂B₂). Overall, S₁B₃ can be introduced as the best intercropping method.     

Can phosphorus (P)-releasing bacteria and earthworm (Eisenia fetida L.) co-enhance soil P mobilization and mycorrhizal P uptake by maize (Zea mays L.)?

Journal of Soils and Sediments - Both earthworm (Eisenia fetida L.) and phosphorus (P)-releasing (PR) bacteria, including organic P-mineralizing (OPM) and inorganic P-solubilizing (IPS), are able...     

Effect of nitrogen– boron interaction on plant growth and tissue nutrient concentration of canola (Brassica napus L.)

Pot experiments were conducted in the greenhouse on a calcareous soil to study the effect of nitrogen on the alleviation of boron toxicity in canola (Brassica napus L.). The treatments consisted of factorial combination of six levels of B (0, 2.5, 5, 10, 20, and 40 mg kg^?1 as boric acid), and four levels of nitrogen (N) (0, 75, 150 and 300 mg kg^?1 as urea) in a completely randomized design with three replicates. Boron (B) application significantly reduced the yield, whereas N addition alleviated the growth suppression effects caused by B supplements. Boron concentration increased with addition B. However, boron concentration in shoot declined with increasing N levels. Increasing N and B rates increased N concentration. Soil application of B increased proline concentration. However, the supply of N decreased it. Generally, application of B decreased potassium (K):B and calcium (Ca):B ratios, chlorophyll concentration, while N application increased them. It is concluded that N fertilization can be used effectively in controlling B toxicity in canola grown in B-affected soils.     

The influence of soil aeration on growth and elemental absorption of greenhouse‐grown seedling pecan trees

Abstract

‘Dodd’ pecan seedlings were exposed to 3 levels of soil aeration for 30 days; 100%, 5%, and 0% of the container surface exposed to the atmosphere. These treatments resulted in about 21%, 13.5%, and 3% soil O₂and 0.3%, 5%, and 13% soil CO₂for 100%, 5%, and 0% of the container surface exposed, respectively. Restricting soil aeration induced partial stomatal closure, and decreased leaf number, leaf area, and leaf, trunk and root dry weights. The decrease in root dry weight associated with reduced soil aeration exceeded the decrease in top dry weight by about 50%. Translocation of N and P to the leaves was reduced when soil aeration was restricted, but root N and P concentrations were increased compared to trees grown in well aerated soil. Leaf elemental concentrations of Ca, Mg, and Mn were lower when trees were exposed to reduced soil aeration. Zinc and Fe concentrations were greater in the roots of trees with low aeration, but leaf and trunk concentrations of Zn and Fe were not affected     

Characterization of “Mais delle Fiorine” (Zea mays L.) and nutritional,morphometric and genetic comparison with other maize landraces of Lombardy region (Northern Italy)

Genetic Resources and Crop Evolution - The loss of agrobiodiversity is a topic of global impact. On a local scale, Lombardy, in the Alpine macro-Region, has lost more than 78% of its plant...     

The effect of subsurface aluminium on the growth and uptake of surface‐applied phosphorus by wheat seedlings 1

Seedlings of four cultivars of wheat (Triticum aestivum L.) differing in tolerance to aluminium (Al) were grown for 14 to 20 days using a split‐root sand/solution culture technique. Each culture tube was divided horizontally into two compartments by a root‐permeable paraffin wax barrier, so that phosphorus (P) and aluminium (Al) supply could be varied in the upper 0–80 mm (surface) and lower 80–180 mm (subsurface) compartments, respectively.

Root growth into the subsurface zone was enhanced by increased P supply to surface roots, but only in the absence of subsurface Al. Where subsurface Al was present, increased P supply to surface roots had no effect on the penetration of roots into the subsurface zone. Tolerance to Al in the cultivars used was therefore not related to the ability to translocate P to sites of Al injury.     

Impact of foliar-applied Hoagland’s nutrient solution on growth and yield of mash bean (Vigna mungo L.) under different growth stages

In a field experiment, various strengths of Hoagland’s nutrient solutions were sprayed to mitigate the deleterious effects of nutrient stresses at different growth stages on mash bean cultivars. Hoagland’s nutrient solution strengths of 0, 25, 50, and 75% were applied at 7, 14, and 21?days after emergence on mash bean cultivars namely Mash-2 and Mash-88. Hoagland’s nutrient solution of 75% strength markedly increased the growth and yield of mash bean cultivars if applied at 21?days after crop emergence. The Mash-88 showed superiority in terms of growth and yield traits as compared to Mash-2. The results suggested that growth and yield was not enhanced effectively by a low strength of Hoagland’s nutrient solution applied at initial growth stages. It is concluded that foliar-applied Hoagland’s nutrient solution of 75% strength can be used as an efficient tool when applied at appropriate growth stage (21?days after emergence) to get optimal yield.