Carbon and nutrient stocks of tea plantations differing in age, genotype and plant population density

Tea (Camellia sinensis L.) is a perennial evergreen shrub managed intensively for continuous growth of young shoots. Most tea plantations were established at the expense of native forest. Change in carbon (C) and nutrient (nitrogen, phosphorus, potassium (NPK)) accumulation in forests over time has been intensively studied, but how C and NPK stocks in tea plantations are associated with age, genotype and plant density have not been reported yet in literature. To get a better insight in the effects of age and the associated change in genotype (clone or seedling) and density on C and NPK stocks data were collected in a chronosequence of tea plantations by destructive sampling of whole tea bushes. Four plantations differing in age (76-, 43-, 29- and 14-year old) and genotype¿density combinations were selected. The 76- and 43-year old plantations were composed of seedlings planted at a relative low density: a spacing of 1.52¿×¿0.91 m and 1.22¿×¿1.22 m, respectively, whereas in the 29- and 14-year old plantations an improved clonal cultivar was grown at higher plant densities: a spacing of 1.22¿×¿0.61 m and 1.22¿×¿0.76 m, respectively. Total dry matter weights (DM) of tea bushes increased with age from 9.0 to 11.5 kg in clonal bushes and from 13.5 and 19.9 kg in seedling bushes for the 14- and 29-year, and the 43- and 76-year old plantations, respectively. Most DM was stored in the woody tissue of the tea bush frame. Total C- stocks expressed per unit area (ha) amounted to 44 and 72, and 43 and 69 t C ha¿1 for clonal and seedling bushes, respectively. Total N stocks ranged from 732 to 995 and from 734 to 1,200 kg ha¿1, P stocks from 78 to 120 and from 67 to 92 kg ha¿1, and K stocks from 775 to 901 and from 646 to 1,120 kg ha¿1 for clonal and seedling bushes, respectively. It is concluded that older stands of seedling and clonal tea plantations result in higher C and NPK stocks. Higher stocks may be functional in maintaining yield stability under adverse weather conditions. Plantations with higher nutrient stocks are less responsive to nutrient supply and therefore will require lower fertilizer applications

'Houd meerdere opties open'

Boeren staan voor de vraag of ze moeten investeren in mestverwerking of niet. Maar de vraag is ook of de samenleving een hightech intensieve veehouderij met mestverwerking accepteert. Je loopt de kans dat als je een deel van het vraagstuk oplost, je de oplossingen van andere aspecten juist moeilijker maak

P-equilibrium fertilization in an intensive dairy farming system: effects on soil-P status, crop yield and P leaching

In the coming decade, European dairy farms are obliged to realize a balance between phosphor (P) inputs to their farmland (in inorganic fertilizers and manure) and outputs (in crop products), the so-called P-equilibrium fertilization. The objective of the present study is to analyze the long-term effects of P-equilibrium fertilization on soil-P status (total soil-P and available soil-P), crop yield and P leaching on dry sandy soil, using data from experimental dairy farm ‘De Marke’, where P-equilibrium fertilization has been applied since 1989. For grassland, P availability is expressed in P-Al and for arable land in Pw. Total and available P status were monitored in the upper topsoil (layer 0–0.2 m). Total soil-P was also monitored in the lower topsoil (layer 0.2–0.4 m) and in the subsoil (0.4–0.6 m). From 1989 to 2006, Pw and P-Al (means of all farmland) decreased by 26 and 25%, respectively. In the same period, mean total-P content of the farmland decreased by 16%. There was a large variation in initial P status (1989) of the various plots. The rate of decline in all soil-P indicators was positively correlated to their initial values. In plots with the lowest initial values, P status did not change, while in plots with high initial values it tended to stabilize at lower levels. At equilibrium-P fertilization, Pw is estimated to stabilize at 20. This is lower than the recommended P status of Dutch soils used for maize cropping. P-Al is estimated to stabilize at 30–40, which corresponds to the current recommendations for grassland. The data show that at P-equilibrium fertilization, soil available-P status is higher in a maize-ley rotation than in permanent grassland. The decline in total P and available P did not affect crop yield, nor did it affect the P concentration in groundwater, but at ‘De Marke’, P emission to groundwater is generally low. The results obtained suggest that P-equilibrium fertilization can be compatible with efficient crop productio

Regionaal nutriëntenmanagement; een verkenning van perspectieven en beperkingen

De van oudsher monofunctionele landbouw verandert steeds meer in een multifunctionele landbouw, waarin meerdere functies van het landelijke gebied worden verweven. Met behulp van regionaal nutriëntenbeheer kan worden ingespeeld op regiospecifieke landbouwkundige, milieukundige en economische randvoorwaarden die aan landbouw worden gesteld. In deze studie zijn perspectieven en beperkingen van regionaal nutriëntenbeheer verkend. Voor veel landbouwbedrijven is een forse inspanning nodig om aan de normenvan het voorgenomen uniforme mestbeleid te voldoen. In sommige regio's zijn wellicht stringentere normen nodig en in andere regio's wellicht minder stringente. Regionaal nutriëntenbeheer speelt hierop in. Perspectieven voor regionaal nutriëntenbeheer liggen vooral in het beheer van nutriëntenstromen tussen verschillende (landbouw)sectoren in een regio, de aanpak van specifieke milieuproblemen, regionale bemestingsadviezen, landbouwvoorlichting en waterbeheer

Method and timing of grassland renovation affects herbage yield, nitrate leaching, and nitrous oxide emission in intensively managed grasslands

Managed grasslands are occasionally ploughed up and reseeded in order to maintain or increase the sward productivity. It has been reported that this renovation of grassland is associated with a flush of soil organic nitrogen (N) mineralization and with a temporary increase in soil mineral N contents. Here, we report on the effects of method and time of grassland renovation on herbage yield, nitrate (NO3 -) leaching and nitrous oxide (N2O) emission. Field experiments were carried out at three sites (two sandy soils and a clay soil) in the Netherlands for three years. Renovation of grassland increased the percentage of Perennial ryegrass from 48–70% up to more than 90%. However, averaged over three years, dry matter yields were higher for the reference (not reseeded) swards (on average 13.6 Mg ha-1 for the highest N application rate) than for the renovated grasslands (12.2–13.1 Mg ha-1 dry matter). Grassland renovation in April did not increase N leaching in comparison to the reference. However, renovation in September increased the risk of leaching, because mineral N contents in the 0–90 cm were in November on average 46–77 kg N ha-1 higher than in the reference. Contents of dissolved organic N (DON) in the soil were not affected by renovation. Renovation increased N2O emissions by a factor of 1.8–3.0 relative to the reference grassland. Emissions of N2O were on average higher after renovation in April (8.2 kg N2O-N ha-1) than in September (5.8 kg N2O-N ha-1). Renovation without ploughing (i.e. only chemically destruction of the sward) resulted in a lower percentage of perennial ryegrass (60–84%) than with ploughing (>90%). Moreover, N2O emissions were higher after renovation without ploughing than with ploughing. Clearly, farmers need better recommendations and tools for determining when grassland renovation has beneficial agronomic effects. Losses of N via leaching and N2O emission after renovation can probably not be avoided, but renovation in spring in stead of autumn in combination with ploughing and proper timing of fertilizer application can minimize N losses

Dryland maize yields and water use efficiency in response to tillage and nutrient management practices in China

Rainfed crop production in northern China is constrained by low and variable rainfall. This study explored the effects of tillage and nutrient management practices on maize (Zea mays L.) yield and water use efficiency (WUE), at Shouyang Dryland Farming Experimental Station in northern China during 2003-2008. The experiment was set-up using a split-plot design with 3 tillage methods as main treatments: conventional, reduced (till with crop residue incoperated in fall but no-till in spring), and no-till. Sub-treatments were 3 NP fertilizer rates: 105-46, 179-78 and 210-92 kg N and P ha. -1 Maize grain yields were greatly influenced by the amount of growing season rainfall, and by soil water contents at sowing. Mean grain yields over the 6-year period in response to tillage treatments were 5604, 5347 and 5185 kg ha, under reduced, no-till and conventional tillage, respectively. Mean WUE was 13.7, 13.6 and 12.6 kg ha mm under reduced, no-till, and conventional tillage, respectively. Mean soil water contents at sowing and at harvest were significantly influenced by tillage treatments. At harvest time, the no-till treatment had ~8-12% more water in the soil than the conventional and reduced tillage treatments. Under conventional tillage, grain yields increased with NP fertilizer application rates. However, under reduced tillage, grain yields were highest with lowest NP fertilizer application rate. In conclusion, grain yields and WUE were highest under reduced tillage at modest NP fertilizer application rates of 105 kg N and 46 kg P per ha. No-till increased soil water storage by 8-12% and improved WUE compared to conventional tillage

P- gebruiksnorm kan nu bedrijfsspecifiek

Een bedrijfsspecifieke fosfaatnorm doet meer recht aan de werkelijke bedrijfsomstandigheden dan de nu geldende forfaitaire normen. Vanaf 2015 mogen we in Nederland niet méér fosfaatmeststof gebruiken dan dat het gewas onttrekt. Verder zullen rijke gronden met teveel aan fosfaat geleidelijk aan 'verarmd' worden tot een aanvaardbaar niveau. Het liefst zonder verlies van opbrengst. Met een rekentool, ontwikkeld door Koeien & Kansen, is het mogelijk gebruiksnormen bedrijfsspecifiek in te schatten

Profilering ontrafeld. Deel II: Rechtsbescherming

In het eerste deel van deze artikelreeks zijn wij ingegaan op enige kaders betreffende data, in het bijzonder profilering onder de Algemene Verordening Gegevensbescherming (hierna: AVG). Wij brachten daarbij de hypothese in stelling dat de Belastingdienst ten aanzien van natuurlijke personen enkel persoonsgegevens verwerkt. De vervolgvraag is hoe een persoon wiens persoonsgegevens door de Belastingdienst worden verwerkt de geldende waarborgen ten aanzien van de verwerking van deze gegevens kan effectueren. In dit tweede deel staat derhalve rechtsbescherming bij gegevensverwerking door de Belastingdienst, en in het bijzonder bij profilering, centraal