Frank Nevens

The application of vegetable, fruit and garden waste (VFG) compost in addition to cattle slurry in a silage maize monoculture: nitrogen availability and use

Abstract In Flanders, vegetable, fruit and garden wastes (VFG) are collected selectively and composted. We studied the effects of the application of this VFG compost on silage maize on a sandy loam soil. A yearly application of 22.5 Mg of VFG compost ha−1, in addition to 42 Mg of cattle slurry ha−1 resulted in economical optimum dry matter yields with a substantial saving of mineral fertilizer N. During the 1st, 2nd, 3rd and 4th year of this compost+slurry application, an additional amount of mineral fertilizer N of, respectively, 94, 43, 22 and 12 kg N ha−1 was needed. Compared to a system with only mineral N fertilization, this implied savings of, respectively, 52, 92, 142 and 134 kg N ha−1. Silage maize N uptake and N concentration in maize were higher when compost was applied. Despite of the low N output/input rate with compost application, it did not result in an excessive amount of residual soil nitrate-N, provided that the additional mineral fertilizer N was adapted to the economic optimum level. Compared to slurry application, 4 years of VFG compost application resulted in significantly higher soil organic matter and total nitrogen concentrations.

The nitrogen- and non-nitrogen-contribution effect of ploughed grass leys on the following arable forage crops: determination and optimum use

Abstract From 1990 to 1998, we studied the N release from ploughed 3-year-old grazed grasslands in the subsequent three seasons of forage crops on a sandy loam soil. Silage maize in the ley–arable rotation outyielded continuous maize on permanent arable plots by 85, 21 and 2% at mineral N fertilization rates of respectively 0, 75 and 180 kg N ha −1 . This decreasing yield effect with increasing N fertilization indicated that the ley–arable rotation effect was mainly a N-contribution effect. The N release was highest during the first year; it decreased during the second and third year following the grassland ploughing. Economically optimum N fertilization rates for silage maize in these years were respectively 2, 139 and 154 kg N ha −1 . Simultaneously, on permanent arable plots this was respectively 152, 191 and 183 kg N ha −1 . This resulted in comparable yields (19.75 Mg DM ha −1 year −1 ) but with a possible saving of 231 kg of mineral N fertilizer ha −1 in a 3-year silage maize period following the ploughed leys compared with continuous silage maize. The N uptake by silage maize on temporary arable plots following grasslands was higher than on permanent arable plots, owing to the higher yields but also to an increased N concentration in the crop on the temporary arable plots. Starting the arable forage crop sequence with fodder beet following the grassland ploughing and adjusting the N fertilization to the enhanced N release minimized the risks on high amounts of residual soil N and hence N leaching losses.

Crop rotation versus monoculture; yield, N yield and ear fraction of silage maize at different levels of mineral N fertilization

Dry matter (DM) yields, N yields, ear fractions and economically optimum N fertilizer rates for silage maize were determined in monoculture and in rotational cropping on a sandy loam soil in Flanders. Rotationally cropped silage maize resulted in higher DM yields, higher N yields and higher ear fractions. These positive effects decreased with increasing mineral N fertilization. With both rotational cropping and monoculture, economically optimum maize yields were obtained with a lower N fertilizer input than was the case for the physically optimum yields, and the optimum N rate was likely to decrease further if the future N fertilizer use will be restricted by levies or higher fertilizer prices. The gradual increase in yield potential of silage maize resulting from plant breeding was expressed better and was exploited in a more efficient way when maize was grown in rotation than when grown in monoculture.

Operationalising eco-efficiency in agriculture: the example of specialised dairy farms in Flanders

Eco-efficiencies of a representative set of Flemish dairy farms were determined for the years 19891990 and 20002001. Eco-efficiency was measured as a combination of nitrogen (N) use efficiency and energy use efficiency, where N use efficiency (l milk kg-1 N surplus) is the ratio between the amount of produced milk and the farm-gate N surplus (= N input − N output). Energy use efficiency (l milk 100 MJ-1) is the ratio between the amount of produced milk and the total (direct + indirect) energy input. Between 19891990 and 20002001, average N use efficiency increased from 27 to 40 l milk kg-1 N surplus and average energy use efficiency increased from 22 to 27 l milk 100 MJ-1, indicating an overall increase of eco-efficiency of the Flemish dairy farms during those periods. The farms with the highest eco-efficiencies were characterised by a higher milk production, a lower N surplus, a lower energy input and a higher gross value-added. The latter shows that on the studied farms, eco-efficiency went hand in hand with better economic results.