Three years of field trials have been carried out in Zaragoza, Spain, using different biodegradable mulch materials in processing tomatoes. The aim was to evaluate weed control with several biodegradable mulches as alternatives to black polyethylene (PE) mulch. The treatments were rice straw, barley straw, maize harvest residue, absinth wormwood plants, black biodegradable plastic, brown kraft paper, PE, herbicide, manual weeding, and unweeded control. Assessments focused on weeds and on crop yield. A laboratory study showed that 1 kg/m2of organic mulch was sufficient to cover the soil for rice, barley straw, and maize harvest residue. The most abundant weed species in the field were purple nutsedge, common purslane, common lambsquarters, and large crabgrass and a change in weed composition was observed between treatments and years. Most weed species were controlled by the mulching materials except that purple nutsedge was controlled only by paper mulch. The other species were well controlled by PE and biodegradable plastic and also by some of the organic mulch treatments. Best weed control and lowest weed biomass were achieved by paper followed by PE and biodegradable plastic. The best organic mulch was rice straw and the worst weed control was from absinth wormwood. Tomato yield was highest for PE followed by paper, manual weeding, biodegradable plastic, and rice straw and was clearly related to weed control. Paper, biodegradable plastic, and rice straw are potential substitutes for PE and herbicides.
Management practices, geographical gradients and climatic factors are factors explaining weed species composition and richness in cereal fields from Northern and Central Europe. In the Mediterranean area, the precise factors responsible for weed distribution are less known due to the lack of data and surveys. The existence of weed survey data of year 1976 in the Zaragoza province of the Aragón region, Spain, offered us the opportunity to compare present weed species with weed species growing 30 years ago. No detailed comparison of changes in weed species composition in cereal fields in that period of time has been conducted in the Mediterranean area. Here a survey was conducted in the Aragón region from 2005 to 2007. Weeds were surveyed in 138 winter cereal fields in ten survey areas where winter cereals are the main crops, using the same methodology applied 30 years ago. In the Zaragoza province, 36 fields were chosen in the same municipalities than in the previous survey. Several management, geographic and climatic variables of each field were recorded and related to weed species with multivariate analysis. Diversity index were calculated and related to survey area and altitude. Our results show that out of the 175 species only 26 species were found in more than 10% of the surveyed fields. The main species were Papaver rhoeas, Lolium rigidum, Avena sterilis and Convolvulus arvensis found in more than half of the surveyed fields. L. rigidum was related to dryland, while the other species were found overall. Furthermore, we found that management, geographical and climatic factors were significantly related to weed species distribution. In particular altitude, survey areas, irrigation and herbicide use in post-emergence were the most driving factors explaining weed species distribution. Species richness was higher in survey areas with extensive management practices and increased with altitude excepting a very productive area with intensive management practices at high altitude where richness was as low as in the irrigated lowlands. The main differences found between the 1976 and the 2005-2007 surveys were (1) the striking increase of grass weeds, (2) the high decrease of mean weed species number found in each field declining from 9 to 3 and (3) the frequency decrease of many weed species probably caused by agriculture intensification in that period of time. The growing importance of other weed species is probably related to their adaptation to minimum tillage, which is a widespread technique nowadays.
Mulch materials of different origin and colour are available in the agricultural sector as sustainable alternatives to the use of polyethylene (PE). Mulching modifies soil temperature and consequently affects crop yields. This work assessed the thermal and productive responses of different mulch materials in two different geo-climatic conditions during a 3-year integrated field study on processing tomato (Lycopersicon esculentum Mill.). Two biodegradable plastic mulches (BD1, BD2), one oxo-degradable material (OB), two types of paper (PP1, PP2) and one barley-straw cover (BS) were compared with two control treatments: black PE and manual weeding (MW). Soil temperature variables (maximum, minimum and mean temperature, soil growing degree-days and soil temperature amplitude) and production variables (marketable and total yield, mean fruit weight) were considered. Thermally, PE could be considered an atypical mulch causing higher temperatures in the soil, but it is not associated with a higher yield. Responses of PE, PP2 and MW were independent of the geo-environmental conditions, whereas OB, BD1 and BD2 had similar thermal and productive responses to each other in different environments. Tomato yield was correlated positively only with the minimum soil temperature, especially when excluding PE.
Summary Boundary structure can hinder or facilitate disturbance of the boundary vegetation by farming practices, such as herbicide and fertiliser drift and occasional cultivation; this may affect their potential role as a weed reservoir. It would be relevant for researchers, farmers and legislators to know whether relationships exist between boundary structure and weed abundance and frequency in boundaries and adjacent fields. In this study, we present a classification of arable field boundaries based on five descriptors: presence of a bank, width, percentage cover of woody and evergreen perennials (WEP), presence of a stonewall and presence of trees. Five types of boundaries are identified, ranging from structurally simple ones (flat, narrow, dominated by annual species) to structurally complex ones (presence of a bank, more than 3 m wide, dominated by WEP). Data from three Spanish regions were used to validate this classification, and the five boundary classes contained different plant communities. Structurally simple, flat and narrow boundaries contained many of the weed species found also in the field centre and with high abundance. More complex, wider boundaries with a slope and a WEP >60%, had a lower probability of hosting the main weeds present in the field centres. Assessment of weed frequency and abundance gave complementary information. The proposed classification of field boundaries may be easily used by farmers and allows adjustment of field margin management to risks posed by the field boundary, in terms of hosting common weeds of arable crops.
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