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Enhanced biological N2 fixation and yield of faba bean (Vicia faba L.) in an acid soil following biochar addition: dissection of causal mechanisms
(Springer Nature, 2015-10) Van Zwieten L; Rose T; Herridge D; Kimber S; Rust J; Cowie A; Morris S; Lehman J
Background and aims: Acid soils constrain legume growth and biochars have been shown to address these constraints and enhance biological N2 fixation in glasshouse studies. A dissection of causal mechanisms from multiple crop field studies is lacking. Methods: In a sub-tropical field study, faba bean (Vicia faba L.) was cultivated in rotation with corn (Zea mays) following amendment of two contrasting biochars, compost and lime in a rhodic ferralsol. Key soil parameters and plant nutrient uptake were investigated alongside stable 15 N isotope methodologies to elucidate the causal mechanisms for enhanced biological N2 fixation and crop productivity. Results: Biological N2 fixation was associated with plant Mo uptake, which was driven by reductions in soil acidity following lime and papermill (PM) biochar amendment. In contrast, crop yield was associated with plant P and B uptake, and amelioration of soil pH constraints. These were most effectively ameliorated by PM biochar as it addressed both pH constraints and low soil nutrient status. Conclusions: While liming resulted in the highest biological N2 fixation, biochars provided greater benefits to faba bean yield by addressing P nutrition and ameliorating Al toxicity.
Some effects of boron to the growth and chemical composition of sainfoin (Onobrychis viciaefolia scop.) : a thesis presented in partial fulfilment of the requirmeents for the degree of Master of Agricultural Science in Plant Science at Massey University, Palmerston North, New Zealand
(Massey University, 1982) Juan, Nenita Fabros
Some effects of boron on the growth and chemical composition of sainfoin (Onobrychis viciaefolia Scop.) plants cv Fakir were evaluated in a glasshouse. The growth and development of sainfoin plants was not affected by the different levels of boron applied but was affected by nitrogen application and inoculation due to the nodulation failure of the latter. Generally, the root showed the highest dry matter yield and the fastest relative growth rate. Similarly, the total nonstructural carbohydrates of the sainfoin plants were not affected by the different levels of boron. Nitrogen application reduced the total nonstructural carbohydrates of the whole plant. Moreover, when 1 ppm boron was applied, both the shoot and the root yielded the highest total nonstructural carbohydrates. Likewise, root and shoot total nonstructural carbohydrates were reduced by the application of nitrogen. Roots gave a higher total nonstructural carbohydrate yield than the shoot. Boron content of the whole sainfoin plant, the shoot and the root ranging from 0-55 µg/g increased in proportion with the increment of boron applied. Similar results were obtained from boron uptake of the whole plant, the shoot and the root. There was a depression of boron concentrations and boron uptake of the whole plant, the shoot and the root, when nitrogen was applied, implying a deficiency situation. Although nonsignificant effects of boron levels were obtained from nitrogen and phosphorus concentration and uptake, respectively, of both shoot and root, application of 2 ppm boron reduced the concentration of nitrogen but not nitrogen uptake, and reduced phosphorus concentration and phosphorus uptake. Application of nitrogen increased shoot and root nitrogen contents and nitrogen uptake but decreased root and shoot phosphorus concentrations and phosphorus uptake. It was concluded that levels of 2 ppm boron concentration were not adequate to support satisfactory growth when plants were supplied with sufficient levels of other nutrients. Keywords: Boron, nitrogen, Rhizobium, total nonstructural carbohydrates (TNC)
Boron dynamics and availability in Pinus radiata plantation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science, Institute of Natural Resources, College of Sciences, Massey University, Palmerston North, New Zealand
(Massey University, 2012) Khan, Raza Ullah
Pinus radiata is an important forest species in New Zealand. Over 89 % of the country’s plantation forestry area is planted with P. radiata. The species makes a major contribution to New Zealand’s $3.1 billion to GDP and the plantation area is projected to increase to 2.5 million hectares by 2025. Research work to date has recognised that soil B deficiency is a major issue in many forestry plantation areas. Edaphic and environmental conditions such as the coarse texture pumacious soils planted with radiata in the Central North Island, and summer drought condition in some areas, further aggravate B deficiency in New Zealand soils. Boron deficiencies in P. radiata lead to growth defects in afflicted plants and a deterioration in wood quality and market value. The primary objective of this thesis was to assess the impact of ulexite, a slow-release B fertiliser, on the bioavailability of soil B, plant B uptake, and the relative effect of B application rate on plant growth and soil microbial activity. A further objective was to compare the rate of B adsorption to seven benchmark soils collected from the North Island of New Zealand. The purpose of the work was to propose a long-term slow-release fertiliser management solution for radiata pine forestry that may mitigate the economic damage caused by B deficiency in this important primary production sector. Soil was collected from Taupo, the major P. radiata planting district in the Central North Island of New Zealand, and used to establish glasshouse studies with P. radiata at Massey University in Palmerston North. Plants for this research were obtained from the Forest Research Institute (SCION) in Rotorua, New Zealand. Two growth experiments were conducted. The second of these compared the B dynamics of a fast-growing and slow-growing clone of P. radiata. The background concentration of B in this soil (less than 0.5 mg/kg calcium chloride extractable B) is low, and B fertiliser application induced a soil response. Results showed that the concentration of plant-available B (extracted using hot 0.02 M CaCl2) significantly increased with B application. Boron application at the highest level (32 kg/ha) led to a build-up of soil B to a critical toxicity level with the subsequent appearance of toxicity symptoms in plants. Application of B resulted in rapid B uptake as shown by an increase in B concentration in all plant parts (needle, stem and roots), but with the greatest rate of increase in needles. The percentage distribution of B throughout the plant showed that B distribution was influenced by B application treatments. The root to needle B ratio is used in this work as an index of B transfer from source to sink parts of a plant. Results showed that under deficient and toxic soil B concentrations (defined through the CaCl2 extractable B concentration), B was restricted to source tissues. However, B application at the rate of 4 kg/ha enabled B to move to sink parts including the new emerging needles. Regardless of clone and B treatment, needles, particularly older needles, were the main site of B accumulation followed by roots and stem. The B concentration in needles of Clone 37 was higher than in Clone 18 and this result reflects a higher demand of B for the faster growing Clone 37 relative to Clone 18. Application of B affected P. radiata growth in terms of height, diameter and plant dry weight. Plants responded positively to B application over a range of fertiliser treatments (8-16 kg/ha) leading to sufficiency in soil as quantified through increases in the plant growth parameters plant height and dry weight. Boron application improved plant physiology as quantified by photosynthesis in this study. Results showed that photosynthesis positively responded to B application up to 8 kg/ha, however a further increase in B application resulted in a decline in photosynthetic activity. Results from a B fractionation study showed that the plant unavailable residual-B fraction was the major form of B in the Taupo soil. With B fertiliser application the concentration of readily-available B increased proportionally to the B application rate. This increase in readily-available B demonstrates the importance of using B fertiliser to provide for a long-term increase in plant-available soil B for P. radiata plantations on the Taupo soil. Soil microbial and microbiological properties also responded to B application. Soil dehydrogenase activity, an index of microbiological activity in soil, showed a concentration gradient from the bulk to rhizosphere soil. Regardless of clone there was approximately a three-fold higher dehydrogenase activity in the rhizosphere soil compared to the bulk soil. Maximum dehydrogenase activity was recorded by a B application at 4-8 kg/ha in both clones with a decrease in activity at higher rates. Regardless of the radiata clone used, mycorrhizal colonisation increased with B application. However, for both clones the maximum mycorrhizal infection on roots was recorded for a B application rate of 2-4 kg/ha. A B adsorption study performed using seven benchmark soils collected from around the North Island showed that B adsorption increased in all soils with the concentration of B in equilibrium solution. Langmuir and Freundlich isotherms modelled B adsorption in all seven soils. Further studies showed that B adsorption corresponded to pH in solution and linearly increased up to pH 9 and reduced thereafter. The results from this study demonstrate the importance of B fertiliser to P. radiata plantation forestry. Both plant and microbiological parameters are affected by both low and excess levels of soil B. Therefore, it is suggested that a B application rate in the range of 4-8 kg/ha is optimal for plant growth and will have no harmful effect on soil microbiological parameters. In contrast, B application at the rate of 16 kg/ha is toxic to both plants and soil microbes and will lead to inhibitory effects on activity and growth.

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