Nutrient Release Dynamics Research Articles

Foliage decomposition and nutrient release dynamics of Bambusa balcooa and Bambusa pallida in a 9-year-old jhum fallow

Litter decay and nutrient release rates of leaf and leaf sheath litters of Bambusa balcooa Roxb. and B. pallida Munro were determined using the litter-bag technique in a 9-year-old jhum fallow in the humid tropics of north east India. C concentration was highest in leaf and leaf sheath litters of B. pallida, while N and lignin concentrations were greater in B. balcooa litter. Both leaf and scale leaf litters of B. balcooa and B. pallida showed similar decomposition patterns. The daily decay constants did not differ significantly between the two litter types and among bamboo species studied. Nonetheless, mass-loss rates during decomposition of the leaf and leaf sheath litters of both the species showed positive correlations with incubation period (the time after burying the samples in the soil). In general, until 120 days of incubation, there was N immobilization and later during the study period rapid release occurred. The release of N from B. pallida is greater than B. balcooa as per KN values. P was initially being immobilized followed by a gradual release after 120 days of litter decomposition in B. balcooa. In B. pallida, no definite pattern was observed. The rate of weight loss and N release showed significant positive relationships with lignin and N concentrations and lignin/N, C/P and N/P ratios, and negative relationships with C and P concentrations and C/N ratio. However, release rates of P did not show significant correlations with most chemical compositions of the litter except with initial P concentration, C/P ratio and lignin/N.

Residue Decomposition and Nutrient Release Dynamics from Two Tropical Forage Legumes in a Kenyan Environment

Soil fertility decline is one of the factors limiting food production on the east coast of Africa. Increased awareness by smallholder farmers of the role of legumes as sources of food and fodder and for soil fertility improvement has stimulated research on the influence of herbaceous legumes in various cropping systems. Decomposition and nutrient release from foliage of legume species clitoria (Clitoria ternatea L.) and dolichos (Lablab purpureus L.) planted in monoculture and as an intercrop with tropical food crops cassava (Manihot esculenta Crantz) and maize (Zea mays L.) were evaluated under field conditions in fine‐loamy, kaolinitic, isohyperthermic, arenic Paleustalfs. The nylon mesh bag technique was used to obtain data to calculate the residue decomposition and nutrient release rates of the clitoria foliage cut every 6 or 10 wk and dolichos foliage cut at 2 or 4 mo. Asymptotic models provided the best fit for both dry matter decomposition and nutrient release. Legume residue decomposition rates (k) were unaffected by cropping system, with values of 0.2 and 0.5 wk−1 for clitoria and dolichos, respectively. Across cutting management strategies, the general order of nutrient release for clitoria at 6 or 10 wk was K > P > Mg > N; while that of dolichos was K > Mg > P > N and K > P > Mg > N for cuts at 2 and 4 mo, respectively. Overall, the residue N, P, and Mg release curves became asymptotic shortly after 60% of the nutrients had been released. Clitoria and dolichos showed their potential to become sources of nutrients for associated crops while protecting the soil surface.

The effects of vegetation control and fertilization on net nutrient release from decomposing loblolly pine needles

This study examined the effects of vegetation control and nitrogen + phosphorus fertilization on decomposition and nutrient release dynamics of loblolly pine (Pinus taeda L.) needle litter. Needle litter was placed in litterbags and left to decompose on the forest floor, and changes in mass loss and nutrient (N, P, K, Ca, Mg, S, Mn, Zn, B, Cu) concentrations and contents were observed at 2- to 6-month intervals for 32 months. Fertilization had no effect on mass loss, while vegetation control resulted in a warmer and drier forest floor and led to reduced mass loss (k = 0.39 and 0.28 year–1for fertilization and vegetation control, respectively). Concentrations of N, P, Ca, S, Zn, and Cu in the decomposing litter increased two- to three-fold over the 32 months, while concentrations of K, Mg, Mn, and B declined, increased, or did not change depending on time and treatment. Based on the release dynamics, the nutrient mobility series was as follows: Cu [Formula: see text] N [Formula: see text] S < P < Zn [Formula: see text] Ca < K [Formula: see text] Mn < Mg [Formula: see text] B. Fertilization had no effect on release dynamics; however, vegetation control reduced release of N, P, S, and Zn, and increased release of B. The mineral soil may be the main source of plant available N and P in midrotation southern pine stands based on the slow release of these elements from decomposing needle litter.

DINÂMICA DA DECOMPOSIÇÃO E LIBERAÇÃO DE NUTRIENTES DA PALHADA DE AVEIA PRETA E NABO FORRAGEIRO CORTADAS EM DIFERENTES ESTÁGIOS DE DESENVOLVIMENTO

O trabalho foi conduzido na área experimental da Fundação ABC, Fazenda Capão do Cipó, no município de Castro/PR. No período de 13/05/1998 à 30/01/1999 com objetivo de avaliar a dinâmica da decomposição e liberação de nutrientes (N, P, K, Ca e Mg) da palhada das coberturas de inverno, envolvendo as culturas de aveia preta (Avena strigosa Schreb) e nabo forrageiro (Raphanus sativus L.). O delineamento experimental empregado foi de blocos ao acaso em fatorial. Os tratamentos testados foram resultantes das combinações das duas coberturas de solo (aveia preta e nabo forrageiro), cortadas em três estádios de desenvolvimento: vegetativo (94 dias), florescimento (103 dias) e pleno florescimento (116 dias) e com cinco épocas de coleta dos materiais para avaliação da liberação de nutrientes. Os resultados das avaliações foram submetidos a análise de variância e regressão, sendo feito o ajuste a um modelo matemático que descreve a perda de massa no tempo, segundo (BADRE et al, 1998). Este modelo exponencial relaciona a taxa de decomposição da massa bem como da liberação de nutrientes como uma função quadrática do tempo (t). O modelo matemático usado foi: M(t) = M(o) Exp.t(at + b). A produção de massa seca não diferiu entre as espécies sendo maior nas condições de florescimento e pleno florescimento em relação ao estádio vegetativo, tanto para aveia como para o nabo forrageiro (p < 0,01). O modelo exponencial se ajustou perfeitamente à taxa de mineralização da massa seca (MS) com o tempo (p < 0,01) para ambas espécies e os estádios avaliados, cujos coeficientes variaram em função das diferenças quanto à relação carbono/fósforo (C/P), celulose e hemicelulose (FDN), para as espécies (p < 0,01) e não entre os estádios (p > 0,05). A relação carbono/nitrogênio (C/N) e lignina, sílica e cutina (FDA) foram diferentes entre os estádios (p < 0,05), mas não para as espécies (p > 0,05). Para a liberação de nutrientes o modelo exponencial indicou ser altamente significativo (p < 0,01) para todos os nutrientes avaliados independente das espécies e dos estádios de desenvolvimento.

Nutrient release dynamics in decomposing leaf litter in two Mediterranean deciduous oak species

La dynamique qualitative et quantitative de la perte d'elements majeurs a partir de litieres de feuilles en decomposition a ete etablie pour deux especes de chenes caducifolies, l'une en Espagne : Quercus pyrenaica, implantee sur Cambisols humiferes (sols brun forestier), l'autre en France : Quercus lanuginosa, implantee sur Leptosols rendsiques (Rendzines). Les memes mecanismes ont ete etudies apres echange de litieres entre la station francaise et une station espagnole. Des sachets de nylon, de maille de 1 mm 2 , contenant chacun 10 g de feuilles ont ete deposes dans cinq stations (quatre en Espagne et une en France) et des echantillons recoltes tous les 2 mois. Sur ces echantillons on a dose : N, P, Ca, Mg et K. Les teneurs en elements majeurs des feuilles diminuent au cours des 36 mois d'etude. Les quatre stations a Q pyrenaica peuvent etre regroupees en deux groupes, indiquant des processus de decomposition differents, sans relation avec les quantites de litiere arrivant annuellement au sol. Pour Q lanuginosa, les resultats etaient similaires a l'un des deux couples espagnols. Au cours de l'experience d'echange de litieres, des dynamiques semblables ont ete observees dans les stations d'origine des litieres et apres echange. K est libere le plus rapidement, suivi de Mg et de P. On a trouve une accumulation relative de Ca dans les litieres de Q pyrenaica, superieure a celle des litieres de Q lanuginosa. Concernant l'azote les resultats sont variables, a la fois entre les deux especes et entre les deux localites.

Decomposition and Nutrient Release Dynamics of Two Tropical Legume Cover Crops

AbstractShifting agriculture is a main contributor to deforestation in the humid tropics. Substitution of managed fallows using cover crops is a possible alternative to natural fallow that may contribute to more sustainable farming systems via more efficient nutrient cycling. Our objective was to determine the rate of decomposition and nutrient (N, P, K, Ca, Mg) release patterns resulting from two managed fallow periods (12 or 18 mo) for Desmodium adscendens (Sw.) DC. (syn. D. ovalifolium Guillemin & Perrottet) and Pueraria phaseoloides (Roxb.) Benth. (tropical kudzu) grown on Typic and Aquic Dystropept soils at two locations in the Bolivian Amazon. Dry matter disappearance and nutrient release rates from decomposing cover crop residues were monitored using 1‐mm mesh nylon bags. The longer managed fallow (18 mo) reduced the decomposition rate of both cover crops. After 30 wk, residues remaining from 12‐mo managed fallows averaged 24% for desmodium and 16% for pueraria, whereas residues from 18‐mo managed fallows averaged 53% for desmodium and 32% for pueraria. Similar to dry matter disappearance, cover crops grown for 12 mo released nutrients faster than those grown for 18 mo. Nutrient release patterns between sites were similar. By 30 wk, nutrient percentages remaining in desmodium vs. pueraria grown for 12 mo at Site 1 were 46 vs. 17% N, 17 vs. 9% P, 4 vs. 2% K, 36 vs. 20% Ca, and 30 vs. 21% Mg. Similar proportional differences in release patterns were observed for all nutrients except Ca for 18‐mo managed fallows. These results indicate a greater potential for asynchrony between crop nutrient demand and cover crop residue nutrient release for 12‐ vs. 18‐mo managed fallows, and more so for pueraria than desmodium.