Organic Nitrogen in Agricultural Systems

This work summarizes information about organic nitrogen (N) in the agricultural system. The organic N forms in soils have been studied by identifying and quantifying the released organic compounds when soils are acid treated at high temperature, in which the following organic N fractions are obtained: hydrolyzable total N, subdivided into hydrolyzable NH4+-N, amino sugars-N, amino acids-N, and unidentified-N and acid insoluble N, a fraction that remains associated with soil minerals after acid hydrolysis. Nitrogen mineralization and immobilization are biochemical processes in nature. This chapter summarizes how these processes occur in the agricultural system. Then, soluble organic nitrogen (SON), volatilization and denitrification processes, and biological nitrogen fixation (BNF) as a key component of the nitrogen cycle and how it makes N available to plants are also discussed. Finally, we discuss the use of organic fertilizers as N source to satisfy the worldwide demand for organic foods produced without synthetic inputs

Fertirrigação na formação de mudas de rúcula em diferentes substratos

The development of specialized production and marketing of vegetable seedlings has motivated farmers to adopt new technology and crop culture, such as substrate utilization and commercial use of fertirrigation. Thus, the objective of this research was to evaluate different types of substrates with different doses of liquid fertilizer on the formation of rocket seedlings. The experiment was conducted at the Federal University of Grande Dorados - UFGD, Dourados, MS. The experimental design was randomized blocks in factorial scheme 4x3x4, with four replicates with four doses of liquid fertilizer Yogen5® 0, 2.5, 5.0, 10.0 mL L-1 and three substrates: BioPlant®, Vitaplan® commercial humus and oxisol. Sowing in polypropylene with 128 cells by placing three seeds to each cell at a depth of 1 cm. There were two fertirrigations at 17 and 27 days after sowing. At 34 days after sowing the chlorophyll content, leaf number, shoot length, root length, stem diameter, total fresh weight, dry weight and total content of nitrogen, phosphorus and potassium leaf were evaluated. Fertirrigation interfered with the development of rocket seedlings, providing an increase in the number of leaves, shoot length, stem diameter, root length and total fresh and dry weight. The use in oxisol as substrate was not effective in promoting germination of rocket seedlings.O desenvolvimento da produção e comercialização especializada de mudas de hortaliças tem motivado os produtores a adotarem novas alternativas de cultivo e tecnologia, como a utilização de substratos comerciais e o uso da fertirrigação. Assim, objetivou-se com esta pesquisa avaliar diferentes tipos de substratos com diferentes doses de fertilizante líquido na formação de mudas de rúcula. O experimento foi conduzido na Universidade Federal da Grande Dourados - UFGD, município de Dourados, MS. O delineamento experimental utilizado foi em blocos casualizados em esquema bifatorial 4x3x4, com quatro repetições, sendo quatro doses do fertilizante líquido Yogen5®: 0; 2,5; 5,0; 10,0 mL L-1 e três substratos: Húmus comercial de Minhoca Vitaplan®, BioPlant® e Latossolo Vermelho Distroférrico. A semeadura ocorreu em bandejas de polipropileno com 128 células colocando-se três sementes em cada célula a uma profundidade de 1 cm. Realizaram-se duas fertirrigações aos 17 e 27 dias após a semeadura. Aos 34 dias após a semeadura foi avaliado o teor de clorofila, número de folhas, comprimento da parte aérea, comprimento das raízes, diâmetro do colmo, massa fresca total, massa seca total e o teor de nitrogênio, fósforo e potássio foliar. A fertirrigação interferiu no desenvolvimento das mudas de rúcula, proporcionando incremento no número de folhas, comprimento da parte aérea, diâmetro do coleto, comprimento da raiz e massa fresca e seca total. O uso do Latossolo Vermelho Distroférrico como substrato não foi eficiente em promover a germinação das mudas de rúcula

Phosphorus in Forage Production

The aim in developing this work was to summarize information about phosphorus (P) limitation and dynamic in tropical soils for forage grasses production. The major idea is direct information about limited factors affecting P availability, dynamic of P fractionation, P pools, P forms, P use efficiency, and the 4R’s Nutrient Stewardship’ for P-fertilizer in forage grasses. Organizing these sub-headings in a chapter can result in interesting of how P behaves under tropical soils, in order to take decision to manage P-fertilizer to accomplish forage grasses production with social, economic, and environmental benefits. As the most limiting nutrient in tropical soils, P-fertilizer in forage grasses can be more effective if the best management practices are followed. In order to avoid excess P-fertilizer application in soil or P-fertilizer response with low efficiency, it is important to understand the P dynamic and the factors associated with P adsorption in soil. Even with low amount of P requested to forages species, the P available in soil is quite low, and this knowledge is primordial to direct P-fertilizer. Tropical soils are quite limited in P content, due to the natural formation with parental material poor in P content and highly weathering condition. Thus, in order to improve phosphorus use efficiency, the 4R’s must be followed to improve P use efficiency (PUE). It is not easy to improve PUE in highly weathering soil with high buffering capacity; however, all the combination of best management practices for P-fertilizer application can result in better use efficiency. Based on the scarcity of natural P-sources in the whole world, the use of alternative P-sources should be incentivized, and more researches about this issue are need for better understanding

Best Management Practices (BMPs) for Nitrogen Fertilizer in Forage Grasses

There is a concern about the growing population and limitation in natural resources which are taking the population to direct its agricultural systems into a more productive and efficient activity, looking to avoid a negative impact on the surrounding environment. The industry energy expended to produce nitrogen (N)-fertilizer is considered an indirect consumption of energy in agriculture, which is higher with an increasing forage yield. Nitrogen is the key nutrient associated with high-yielding production in forage grass and grain crops. The aim of this chapter is to introduce the best management practices (BMPs) for N-fertilizer application in forage grasses to improve N-use efficiency, since the most economical way to feed livestock is forage plants where its potential biomass production is not well explored. The BMPs basically follow three management practices: (1) soil nutrient availability and forage requirement, (2) fertilizer application, and (3) decrease in nutrient losses from soil. In order to take a decision on applying N-fertilizer to accomplish forage grasses production with social, economic, and environmental benefits, the N-fertilizer use in forage grasses is going to follow the “Right rate, Right source, Right place, and Right time (4R) nutrient stewardship.” The application of the 4R’s nutrients stewardship is directly associated with economic, social, and environmental impact. The capacity of the 4R’s implementation worldwide turns into a best guide to improve the striving of better N-use efficiency in forage grass. The 4R’s are interrelated; thus, the recommendation of N-fertilizer rates cannot be prescribed without the combination of the 4R’s where a whole system to be followed should be considered to decide about N-fertilizer in pasture. Consequently, any decision in one of the 4R’s is going to affect the expected N-fertilizer results and dry matter production

Nutritional Status of Cotton Plant Assessed by Compositional Nutrient Diagnosis (CND)

The use of compositional nutrient diagnosis (CND) to assess the nutritional status of cotton crop is quite important to improve knowledge on plant nutritional requirement and assist the fertilizer recommendation. The aim of this chapter is to introduce the possibility of using CND for cotton crop. This method has scarcely been used to assess the nutritional status of cotton plant although a few results have indicated that it can be promising. In fact, CND methodology seems to be better in the nutritional diagnosis than traditional methods such as sufficient range (SR) and critical value approach (CVA). Its efficiency has increased with the possibility of applying multivariate analysis, principal component analysis (PCA), canonical correlation, and so on. The application of PCA possibility to note some interactions among the nutrients is important for understanding the dynamics of nutrients in plants

Fractions of organic matter and decomposition of eucalypt harvest residues in Coastal Plain soils of Bahia, Brazil

O eucalipto é a essência florestal mais plantada no Brasil e, quando se visa manter a sustentabilidade da produção florestal, é imprescindível entender os processos de decomposição de litter e o impacto do cultivo do eucalipto nas frações da matéria orgânica do solo (MOS). A conversão de pastagens em florestas plantadas de eucalipto modifica as frações lábeis e humificadas da MOS, mas a magnitude destas alterações é pouco conhecida no bioma da Mata Atlântica de Tabuleiros Costeiros. Assim, nos dois primeiros capítulos deste trabalho são relatadas as mudanças causadas pelo cultivo do eucalipto nos estoques de C e N nessas frações. Os solos selecionados foram amostrados nas profundidades em 0-10, 10-20, 20-40, 40-60 e 60-100 cm, de áreas anteriormente ocupadas por pastagem e, atualmente, cultivadas com eucalipto no final da primeira rotação - eucalipto implantação; eucalipto na segunda rotação cultivado em sistema de reforma eucalipto reformado; pastagem e, mata nativa, esta última tomada como referência. O delineamento experimental foi em blocos casualizados, com seis repetições, sendo os tratamentos analisados em parcelas subdivididas (usos do solo na parcela e profundidades na subparcela). A substituição da mata nativa pela pastagem, e a implantação do eucalipto em área de pastagem ocasionaram reduções nos estoques de C orgânico total (COT), C lábil, C da matéria orgânica leve livre (MOLL) e, substâncias húmicas (SH). No entanto, quando cultivado sob reforma, em 2ª rotação, houve recuperação do estoque de C nestas frações, retornando aos valores similares àqueles do solo sob mata nativa. A pastagem foi o uso do solo que manteve os maiores estoques de nitrogênio (N) em todas as frações da MOS. Assim como o C, a maior parte deste N no solo sob pastagem está associada à fração humina. A análise do C nas SH foi sensível para detectar diferenças entre os diferentes usos do solo, porém, a magnitude dos efeitos são maiores nas frações mais lábeis e de labilidades intermediárias da MOS. O estoque de C da fração mais lábil (biomassa microbiana do solo) não foi diferente estatisticamente nas camadas mais superficiais e somente se detectou diferença significativa quando os estoques foram analisados juntamente com aqueles em maiores profundidades. A adoção do cultivo mínimo, o descascamento do tronco na área de plantio, e o aumento da adubação, especialmente com N, em áreas plantadas com eucalipto, têm gerado resíduos que se acredita serem de melhor qualidade. Todavia, não se têm relatos sobre o tempo de ciclagem dos diferentes componentes do resíduo da colheita e como esta é influenciada pelo teor de N do tecido vegetal. No terceiro capítulo, são apresentados resultados de estudo sobre a dinâmica da decomposição de resíduos de eucalipto, com diferentes composições (com e sem a presença de casca) e teores iniciais de N, em condições climáticas distintas na Bahia. Os resíduos folha e galho utilizados nesse estudo de decomposição foram provenientes de um mesmo local, oriundos de um experimento de adubação nitrogenada. Árvores clonais de híbridos de Eucalyptus grandis com E. urophylla não fertilizadas com N e, árvores que foram submetidas a altas doses de N (320 kg ha-1), com cerca de três anos de idade, foram abatidas e separadas em folha e galho. A casca foi oriunda de um povoamento de clones do mesmo híbrido com 7,4 anos de idade recém colhido. Folhas, galhos e cascas foram secos, pesados e colocados dentro dos litter bags, na forma mais similar àquela encontrada no campo após a colheita, sendo que cada litter bag continha 40 g de resíduo homogeneizado. Os litter bags foram alocados em cinco regiões (Oeste, Central A, Norte, Central B e Sul - listadas em ordem crescente de pluviosidade). Os tratamentos consistiram de: duas composições de resíduo (folha + galho, com ou sem casca), duas qualidades nutricionais (maior ou menor teor inicial de N); cinco épocas de coleta (0, 1, 3, 6 e 12 meses), dispostas em cinco regiões do Estado da Bahia. O delineamento experimental utilizado foi em blocos casualizados, com cinco repetições, e os tratamentos dispostos em parcelas sub-sub-divididas (parcelas = tratamentos, subparcelas = regiões e sub-sub-parcelas = tempo). Os resíduos com maiores teores iniciais de N e em regiões com maiores precipitações pluviais foram mais rapidamente decompostos. O tempo necessário para a decomposição de 50 % de todo o resíduo combinado (folha + galho + casca) da colheita (t0,5) variou de 248 a 388 dias para resíduos com maiores teores iniciais de N e, de 322 a 459 dias para resíduos com menores teores iniciais de N. Todavia, com exceção da região Oeste, na presença de casca, os resíduos combinados com maiores teores de N reduziram a constante de decomposição (k) e aumentaram o valor de t0,5. Dos componentes individuais do litter, as folhas foram mais rapidamente decompostas e as taxas de decomposição variaram em função das condições ambientais, sendo mais elevada em regiões de maiores precipitações pluviais. A decomposição do galho foi estimulada pela presença da casca e pelo teor inicial mais elevado de N. Para casca, observou-se comportamento inverso, pois na presença de resíduos com maiores teores iniciais de N, houve menor decomposição. Para galho e casca, a relação C:N e lignina:N foram importantes indicadores da resistência do material à decomposição, pois quanto maior essas relações maior foi a permanência do resíduo na área. Na folha a liberação de N foi similar à dinâmica de decomposição do litter, enquanto que em materiais mais recalcitrantes (galho e casca) foi observada imobilização líquida de N.Eucalypt is the most planted tree in Brazil and to maintain a sustainable forest production it is fundamental do understand the processes of litter decomposition and the impact of eucalypt cultivation on soil organic matter (SOM) fractions. The conversion of planted pastures in eucalypt plantations alters the labile and humified pools of SOM, but little is known about the effects of eucalypt plantations in those fractions in Argisols of Brazilian Coastal Plain. Thus, in the first two chapters of this work it was investigated the changes caused by eucalypt cultivation on carbon (C) and nitrogen (N) stocks in SOM fractions. The selected soils were sampled in the 0- 10, 10-20, 20-40, 40-60 and 60-100 cm depths in areas previously under planted pasture, and currently cultivated with short-rotation eucalypt at the end of the first rotation (implantation eucalypt); eucalypt in the second rotation, as a new stand (reformed eucalypt); planted pasture and, native vegetation (Atlantic Forest), used as a reference. The study was in a completely randomized block design with six replicates, and treatments analyzed as split-plot. The substitution of the native forest for planting pasture, and the implantation of the eucalypt in pasture land reduced total organic carbon (TOC), labile carbon (LC), free light fraction C (FLL) and humic substance (HS) C stocks. However, in the second rotation, when eucalypt was cultivated under reform, there was a recover in C stocks of those SOM fractions, which returned to values similar to those under the native forest soil. The pasture was the soil use that maintained the largest N stocks in all SOM fractions. Similarly to C, most of the N in the soil under pasture is associated to the humin fraction. The analysis of C in HS was sensitive to detect differences among the different soil uses, but the effects were more evident in the labile and intermediate SOM fractions. The soil microbial biomass (BMS) C stocks showed no significant difference among soil uses in surface layers, and significant differences were detected only when C stocks of deeper soil layers were taken into account. The adoption of reduced tillage, the on site debarking, and the increase of fertilization, especially with N, in plantation eucalypt is believed to produce plant residues of better quality and faster cycling rates. However, reports on the decomposition rate of different residue components and how it is influenced by their N content are scarce. In the third chapter, it is presented results on the dynamics of decomposition of individual eucalypt residue components (with and without bark) with distinct initial N content, under different climatic conditions in southern Bahia state, Brazil. The residues (leaves, branches) used in the decomposition study were collected in a nitrogen fertilization experiment, from three year-old clonal Eucalyptus grandis x E. urophylla trees not fertilized with N and from trees that were fertilized with high doses of N (320 kg ha-1). The bark used was from a nearby clonal 7,4 year-old eucalypt plantation that had been recently harvested with a harvester. Leaves, branches and barks were dried, weighed, combined and put inside litter bags, which were then were taken to the field. Each litter bag contained 40 g of residue. The litter bags were allocated in five regions (West, Central A, North, Central B and South) with increasing rainfall. Litter bags were collected at five periods (0, 1, 3, 6 and 12 months) after installation. The treatments consisted of two residue compositions (leaves + branches, with and without bark), two residue nutritional qualities (low and high N content), and five sampling periods (0, 1, 3, 6 and 12 months), in the five geographic regions with distinct rainfall. The experiment was in a completely randomized block design with five replicates (regions), and treatments arranged in a split-split plot design. The residues with higher initial N content and in regions with higher rainfall were more rapidly decomposed. The time required for 50 % of mass loss of the whole combined residue (leaf + branch + bark) (t0,5) varied from 248 to 388 days for residues with high initial N content, and from 322 to 459 days for residues with lower initial N content. However, with exception of the drier, West region, the presence of bark led to smaller decomposition constants (k) and larger t0,5 values for the combined residues that had greater initial N content. Of the individual components of the litter, the leaves were more rapidly decomposed. The decomposition of branches was stimulated by the presence of the bark, the greater initial N content and precipitation. Conversely, the bark that was in the presence of residues with greater initial content was less decomposed. The mass remaining of individual components of residue correlated negatively with N and lignin content. For branches and bark, the C:N and lignin:N ratios were important indicators of the resistance decomposition, because higher ration resulted in smaller mass loss and longer t0,5. The release of N from leaves followed the decomposition dynamics, while in more recalcitrant materials, with lower N initial content (branches and bark) it was observed a temporary net N immobilization.Conselho Nacional de Desenvolvimento Científico e Tecnológic