UROCHLOA GRASS GROWTH AS A FUNCTION OF NITROGEN AND PHOSPHORUS FERTILIZATION

The urochloa grass (Urochloa mosambicensis) is a perennial grass, C4 plant, with a high photosynthetic rate and CO2 fixation, persistent to water deficit, adapted to a wide diversity of soils and hot climate regions. Thus, the objective was to evaluate the urochloa grass growth and define the best models to estimate plant height as a function of nitrogen and phosphate fertilization. The experimental design was completely randomized, in the 2 x 2 factorial design (presence and absence of nitrogen presence and absence of phosphorus), with four replications. Was used a dose of nitrogen and phosphorus equivalent to 100 kg.ha-1 of N and 150 kg.ha-1 of P2O5, respectively. The following models were used: linear, power, gamma andlogistic to estimate plant height as a function of the following explanatory variables: days after planting, nitrogen and phosphorus doses. The criteria used to determine the best model(s) were as follows: higher adjusted coefficient of determination, lower Akaike information criterion, lower sum of square of residuals and high Willmott index. The plant height in the absence of nitrogen and phosphorus and when applied 100 kg.ha-1 of N and 150 kg.ha-1 of P2O5 was estimated more accurately by the Gamma model with high power of explanation. The adoption of the Gamma model allows to estimate the U. mosambicensis plant height, in a non-destructive manner, with high precision, speed and low cost, depending of age plant and nitrogen and phosphate fertilization.

Multivariate management systems of long-term hayfields in the Central Non-Chernozem region of Russia

В Центральном районе Нечернозёмной зоны в 2018–2020 годах изучалось шесть систем ведения долголетнего сенокоса. В среднем за годы исследования применение техногенной системы позволило получить 3,86 т/га сухого вещества (СВ), применение интегрированной — 5,08 т/га СВ, техногенно-органической — 4,75–5,16 т/га СВ, техногенно-минеральной экстенсивной — 3,97–7,13 т/га СВ, техногенно-минеральной интенсивной — 6,60–8,85 т/га СВ, комбинированной — 7,03–7,25 т/га СВ. Существенное влияние на урожайность оказывали погодные условия. В засушливый год не был сформирован полноценный 2-й укос, что не позволило травостоям реализовать потенциал продуктивности. Более эффективно ограниченный запас влаги в почве использовался в техногенно-минеральной интенсивной системе. В условиях достаточной влагообеспеченности был получен полноценный второй укос, составляющий 30–50% сбора СВ за сезон. При улучшении условий увлажнения урожайность наиболее заметно повышалась при применении техногенно-минеральной интенсивной системы. Отмечена высокая экономическая эффективность применения всех изучаемых систем за счёт длительного использования травостоя. В зависимости от технологии рентабельность производства корма составляла 74–220%, себестоимость 1 корм. ед. — 3,12–5,75 руб. Для получения 65,2–88,0 ГДж, 5,1–6,8 тыс. корм. ед. и 781–1153 кг сырого протеина с 1 га на суходольных лугах Центрального района Нечернозёмной зоны рекомендуется применять техногенно-минеральную интенсивную систему ведения сенокоса. В случае недостаточной обеспеченности хозяйств материально-техническими ресурсами рекомендуются техногенная, интегрированная, техногенно-органическая и техногенно-минеральная экстенсивная системы ведения, позволяющие поддерживать высокое участие бобовых видов в травостое, что обеспечивает использование биологического источника азота и позволяет получить с 1 га сенокосных угодий 39,0–56,7 ГДж, 3,1–4,5 тыс. корм. ед. и 462–688 кг сырого протеина. Six management systems for long-term hayfields were tested in the Central Non-Chernozem region in 2018–2020. Without fertilization 3.86 t ha-1 of dry matter (DM) was obtained. Integrated farming resulted in 5.08 t DM ha-1, application of organic fertilizers — 4.75–5.16 t DM ha-1, extensive farming with mineral fertilization — 3.97–7.13 t DM ha-1, intensive farming with mineral fertilization — 6.60–8.85 t DM ha-1, combined management system — 7.03–7.25 t DM ha-1. Weather significantly affected crop productivity. Under drought grasses showed poor growth after the first cut leading to low yield. Intensive farming with mineral fertilization allowed more effective use of soil water resources. Sufficient water availability positively affected grass growth after the first cut resulting in 30–50% of DM yield for a season. The best performance was observed under intensive farming with mineral fertilization. All the management systems provided high economic efficiency due to a long-term cultivation of swards. Payback amounted to 74–220%, prime cost of 1 feed unit — 3.12–5.75 rubles. Intensive farming with mineral fertilization was recommended in order to obtain 65.2–88.0 GJ, 5.1–6.8 thousand feed units and 781–1153 kg of crude protein from 1 ha. In case of insufficient material and technical resources other above-mentioned systems can be used, except for the combined one. These management systems maintained high proportion of legumes in swards, an effective mean to obtain nitrogen via nitrogen-fixing bacteria. As a result, swards yielded 39.0–56.7 GJ, 3.1–4.5 thousand feed units and 462–688 kg of crude protein from 1 ha.

Clover in agriculture: combined benefits for bees, environment, and farmer

Concerns over the increasing cost and environmental impact of high inorganic nitrogen (N) inputs have led to a reappraisal of the role of legumes, particularly clover, in maintaining soil fertility in improved grasslands. Clover and other legumes host the symbiotic root bacteria Rhizobium that fix N, reducing the need for N fertiliser application. Grass plus clover swards are comparable to grass monocultures given medium to high inorganic N inputs in terms of companion grass growth, livestock performance and, yield of subsequently planted crops. Reduced N fertiliser input also reduces associated N leaching into water and greenhouse gas emissions during manufacture, transport, and application. In addition, increased use of clover in grasslands also benefit flower-visiting insects by providing an abundant source of nectar and pollen in summer. This is a critical period due to high levels of competition for these in summer. Because temporary and improved grassland covers almost half (47%) of UK land area this habitat type has great potential in wildlife conservation. Further research is needed on the agronomic and conservation benefits of more diverse swards, as incorporation of additional forb species may complement clovers and legumes to benefit a wider range of flower-visiting insect species. In addition, more information on the attitudes of farmers for or against using clover and legumes in grasslands is needed, as they make the management decisions for most agricultural land in the UK. Implications for insect conservation: increased use of clover is a low-cost way to improve the food supply for flower-visiting insects, while to sustaining agricultural productivity and reducing environmental impact.

Growth stimulators and mineral fertilizers influence on Sudan grass growth, development and productivity

The article considers the results of research on the influence of seeding rates, fertilizers and growth stimulator on the development and productivity of the Sudan grass of the Julia variety in the conditions of chestnut soils of the Volgograd region. In the field two-factor experiment, we studied: factor A - the three seeding rates 1.0, 1.5 and 2.0 million germinating seeds per hectare; factor B - fertilizers and growth promoters: 1. Control without fertilizers; 2. N60 P60 K45 + N30; 3. Growth stimulator Raikat Start; 4. N60 P60 K45 + Raikat Start + N30. The use of mineral fertilizers increased the leaf surface area by 0.3-0.5 thousand m2/ha, the use of growth stimulators increased the leaf surface area by 0.1-0.2 thousand m2/ha, the combined use of mineral fertilizers and growth stimulators increased the leaf surface area by 0.9-1.2 thousand m2/ha. It was found that the highest yield of green mass of Sudan grass, 28.6 t/ha, was formed on the variant with a seeding norm of 1.5 million tons of germinating seeds per ha with the complex application of mineral fertilizers and the growth stimulator Raikat Start.

Testing Combined Effect of Amendments and Inoculation with Bacteria for Improving Phytostabilisation of Smelter Waste Extremely Contaminated with Trace Elements

Smelter waste deposits pose environmental and health threats and require remediation actions. Phytostabilisation techniques, based on soil amendments, help to establish plant cover and limit the secondary emission of potentially toxic trace elements. However, methods to optimize their effectiveness are needed. The application of bacterial inoculants in combination with soil amendments in the remediation of soils and wastes contaminated with metals still has not been extensively tested. Therefore, the aim of this study was to determine the effectiveness of indigenous (Streptomyces sp., Pseudomonas sp.) and foreign (Streptomyces costaricanus) strains of bacteria in supporting grass growth on extremely contaminated waste slag. They were applied alone and in combination with compost mixed with phosphate fertilizer or iron oxide. The tested strains improved plant growth and increased plant availability of phosphorus. The interaction of the soil amendments and some bacterial strains also stimulated a decrease in the extractability of metals, likely through the phosphate-induced precipitation of lead. Our data show that the effectiveness of soil amendments in the phytostabilisation of heavily polluted smelter deposits can be enhanced by plant growth-promoting bacteria (PGPB).

Understanding Grass Invasion, Fire Severity, and Acacia koa Regeneration for Forest Restoration in Hawaiʻi Volcanoes National Park

With invasive grasses increasing wildfire occurrence worldwide, a better understanding of the relationships between native plants, fire, and invasive grass is needed to help restoration plans facilitate ecosystem resilience. Invasive grasses are particularly problematic for altering fire regimes in the tropics, yet in Hawaiʻi, restoration sites are often planted with monocultures of the native tree Acacia koa, which can promote grass growth via nitrogen fixation. This, combined with the difficulty of estimating pre-fire grass cover under thick canopies, complicates attempts to restore Hawaiian ecosystems. We studied the 2018 Keauhou Ranch Fire in Hawaiʻi to investigate three questions: (1) at what level of precision can pre-fire grass cover be accurately estimated from oblique aerial photos? (2) how are post-fire A. koa regeneration densities affected by fire severity? and (3) how are post-fire A. koa regeneration densities affected by pre-fire grass cover and its interaction with fire severity? We collected burn severity and post-fire regeneration data from 30 transects stratified across mid-elevation woodland, montane woodland, and montane shrubland communities. We evaluated visual estimates of pre-fire grass cover from oblique aerial imagery with quantitative in situ data from 60 unburned transects of the same cover types. Pre-fire estimates of grass cover categories were 67% accurate in montane woodland (n = 9) and 100% accurate in montane shrubland (n = 11), but only 20% accurate in mid-elevation woodland (n = 10). In montane woodlands with low pre-fire tree densities, A. koa regeneration densities were higher with increased fire severity, but this trend reversed when pre-fire tree densities were high. We detected no effect of pre-fire grass cover, nor its interaction with fire severity, on A. koa regeneration density. This indicates that restoration through the planting of A. koa may be successful in promoting fire-resilient A. koa forest, although there are potential issues to consider regarding the effects that A. koa’s grass promotion may have on other species within the ecosystem.