Apparent N Balance in Organic and Conventional Low Input Cropping Systems

The determination of nutrient surplus is one of the indicators of potential N losses from the agricultural system to the environment. An experiment was started in 1998 in Central Italy to evaluate the soil surface N balance of an organic and a conventional low input cropping system over a long term crop rotation. Results at the end of a 6-year crop rotation showed an estimated N surplus in organic system 1.3-2 times higher than in conventional system while N content in the top soil was not different in the two systems, so that organic system should have involved a higher N loss from that soil layer

Nitrogen Fertilization Strategies for Organic Wheat Production: Crop Yield and Nitrate Leaching

Nitrogen fertility management represents a crucial aspect for common wheat (Triticum aestivum L.) production, particularly when we deal with organic agriculture. This study was conducted to determine the effect of five N fertilization strategies on yield, grain protein content, and N leaching risk. In a 3‐yr field experiment, a faba bean/wheat temporary intercropping (TIC) and four fertilization treatments with extra‐farm N sources were compared. Extra‐farm N sources were represented by blood meal (BM) and roasted leather (RL) (broadcast all‐at‐once at seeding or split into one‐half at seeding and one‐half at tillering in a side‐dressing application). Unfertilized and mineral fertilized controls were included. The effect of the legume on TIC wheat N uptake was always positive while dry weight accumulation and yield were generally poorly affected. Regardless of the broadcasting method, BM treatments generally showed a slightly higher yield and grain protein content compared to wheat fertilized with roasted leather (this was also confirmed by fertilizer release efficiency). The risk of N leaching was maximum at the onset of drainage (i.e., during the first phase of crop growth), so using organic fertilizers at pre‐seeding stage appeared to be a very risky practice, especially if quick‐N‐releasing ones are used. Splitting the organic fertilizer rate avoided a large amount of mineralized N to be leached in the watershed during the critical stage of drainage onset. The TIC was the best option in terms of environmental preservation, and assured a constantly higher grain protein content compared to the other organic fertilization treatments

Nine-year results on maize and processing tomato cultivation in an organic and in a conventional low input cropping system

Nine-year results on yields and apparent balances of organic matter and nitrogen (N) are reported for maize and processing tomato cultivated in a long term comparison trial between an organic and a conventional low-input system in Central Italy. In every year, above ground biomass and N accumulation of each cash crop and green manure, including weeds, and the partitioning between marketable yield and crop residues were determined. Apparent dry matter and nitrogen balances were calculated at the end of each crop cycle by taking into account the amounts of dry matter and ex-novo N supplied to the system as green manure legume Ndfa ( i.e. an estimate of N derived from the atmosphere via symbiotic fixation) and fertilizers, and those removed with marketable yield. Processing tomato complied with organic cultivation better than maize. As compared to the conventional crop cultivation, organic tomato provided similar yields, used supplied N more efficiently and left lower residual N after harvest, with lower related risks of pollution. Organic maize yielded less than conventional one. The main limitation for organic maize was the low N availability during initial growth phases, due to either low N supply or low rate of N release from incorporated green manure biomass. In both organic and conventional cultivation the system sustainability could be improved by an appropriate crop rotation: wheat in fall winter likely prevented leaching loss of mineral N in both systems; green manure crops in the organic system allowed to either trap and recycle soil mineral N or supply ex novo legume Ndfa to the soil, with benefits in mitigation of N pollution and improvement in self-sufficiency of the system

Processing Tomato–Durum Wheat Rotation under Integrated, Organic and Mulch-Based No-Tillage Organic Systems: Yield, N Balance and N Loss

In a 4-year study, the biannual crop rotation processing tomato–durum wheat was applied to three cropping systems: (i) an innovative organic coupled with no-tillage (ORG+) where an autumn-sown cover crop was terminated by roller-crimping and then followed by the direct transplantation of processing tomato onto the death-mulch cover; (ii) a traditional organic (ORG) with autumn-sown cover crop that was green manured and followed by processing tomato; and (iii) a conventional integrated low-input (INT) with bare soil during the fall–winter period prior to the processing tomato. N balance, yield and N leaching losses were determined. Innovative cropping techniques such as wheat–faba bean temporary intercropping and the direct transplantation of processing tomato into roll-crimped cover crop biomass were implemented in ORG+; the experiment was aimed at: (i) quantifying the N leaching losses; (ii) assessing the effect of N management on the yield and N utilization; and (iii) comparing the cropping system outputs (yield) in relation to extra-farm N sources (i.e., N coming from organic or synthetic fertilizers acquired from the market) and N losses. The effects of such innovations on important agroecological services such as yield and N recycling were assessed compared to those supplied by the other cropping systems. Independently from the soil management strategy (no till or inversion tillage), cover crops were found to be the key factor for increasing the internal N recycling of the agroecosystems and ORG+ needs a substantial improvement in terms of provisioning services (i.e., yield)

Yield and apparent dry matter and nitrogen balances for muskmelon in a long-term comparison between an organic and a conventional low input cropping system

Nine-year yields and apparent balances of dry matter and nitrogen (N) are reported for muskmelon cultivated in a long-term comparison trial between an organic and a conventional low input system in Central Italy. In every year, yield, above ground biomass and N accumulation of each cash crop, green manure and weeds, and the partitioning between marketable yield and crop residues were determined. Apparent dry matter and nitrogen balances were calculated at the end of each crop cycle by taking into account the amounts of dry matter and ex novo N supplied to the system as green manure legume Ndfa (i.e., an estimate of N derived from the atmosphere via symbiotic fixation) and fertilisers, and those removed with marketable yield. Differences between systems varied across years. On average, organic muskmelon yielded 16% less than the conventional one, while the fruit quality was similar in the two cropping systems. Fruit ripening began one week later and it was more scaled than in the crop grown conventionally. This was the consequence of a slow initial growth of the organic crop, due to inadequate green manure N total supply or timing of N release. Moreover such a wide spaced crop (0.5 plants m–2, in rows 2 m apart) was not efficient in intercepting N released from green manure biomass incorporated broadcast. Compared to the conventional crop management, the organic crop management resulted in much higher organic matter supply to the soil and in higher residual N after harvest. Thus, the choice of cultivating wheat just after melon to prevent postharvest residual N loss appears a key strategy especially in organic systems. Fall-winter green manure crops contributed to the self-sufficiency of the organic system by supplying muskmelon with either N absorbed from the soil or ex novo legume Ndfa

Eleven-year results on soft and durum wheat crops grown in an organic and in a conventional low input cropping system

Eleven-year results on yields and apparent balances of organic matter and nitrogen (N) are reported for soft and durum wheat crops grown in the BIOSYST long-term experiment for the comparison between an organic and a conventional low-input system in Central Italy. The N supply to organic wheat consisted of 40 kg N ha–1 as poultry manure plus the supposed residual N left by green manures carried out before the preceding summer vegetable, while the N supply to conventional wheat consisted of 80 kg N ha–1 as mineral fertilisers, split in two applications of 40 kg ha–1 each, at tillering and pre-shooting. In every year, above ground biomass and N accumulation of each wheat species, including weeds, and the partitioning between grain yield and crop residues were determined. Apparent dry matter and N balances were calculated at the end of each crop cycle by taking into account the amounts of dry matter and N supplied to the system as fertilisers, and those removed with grain yield. Soft wheat yielded more than durum wheat. For both species, grain yield and protein content were more variable across years and generally lower in the organic than in the conventional system. In both systems, grain yield of both species resulted negatively correlated with fall-winter rainfall, likely for its effect on soil N availability. Both species caused a lower return of biomass and a higher soil N depletion in the organic than in the conventional system. Our experiment confirmed that winter wheat can help exploit the soil N availability and reduce N leaching in fall winter, especially after summer vegetables, but in stockless or stock-limited organic systems it needs to be included in rotations where soil fertility is restored by fall winter green manures to be carried out before summer crops