Weed control is an important cultivation treatment in the cultivation of maize, while the time of conducting it, limited by the plant developmental stage, determines the yield height and financial outcome. However, the use of chemical plant protection products on ecological farms is not allowed, therefore, the level of obtained yields and economic effects of this species cultivation is largely affected by mechanical regulation of weed infestation. The aim of the study was economic evaluation of maize cultivated for green matter depending on the method of cultivation and dose of a fertilizer in a form of composted manure. Research material were results of the field experiment carried out in the years 2009-2011 at the Experimental Station of the Institute of Soil Science and Plant Cultivation, National Research Institute (IUNG-PIB) in Grabowo (Masovian Voivodeship). Primary factor were manure doses of 20 and 40 Mg·ha^-1, secondary factor were cultivation methods: A – without weed control (control), B – brush weeder, C – weeding hoe, D – brush weeder plus hiller. The production cost specification included direct and indirect costs. Conducted analysis indicated that the yield of green matter of maize was significantly affected by the applied manure doses. The highest yields were observed when a brush weeder was used three times in maize cultivation. Yields of both the fresh and dry matter of maize fertilized with a dose of 20 Mg·ha^-1 were lower than the yields of maize with the application of 40 Mg·ha^-1. Omission of mechanical cultivation while growing maize, regardless of the manure dose, caused reduction in the green matter yield by about 38% compared to plots where the weeds were controlled mechanically. The most beneficial financial results were possible to achieve after using a brush weeder. This method of weed control also ensured obtaining the lowest unit cost in relation to 1 ton of green matter. Positive financial result without area payments was achieved with the use of technological variants, with a lower manure dose (20 Mg·ha^-1), with the use of a brush weeder, weeding hoe, as well as on plots with the use of a brush weeder plus hiller.

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