Multi-cropping Systems Research Articles

Managing Manure Nutrients Through Multi-crop Forage Production

Concentrated sources of dairy manure represent significant water pollution potential. The southern United States may be more vulnerable to water quality problems than some other regions because of climate, typical farm size, and cropping practices. Dairy manure can be an effective source of plant nutrients and large quantities of nutrients can be recycled through forage production, especially when multi-cropping systems are utilized. Linking forage production with manure utilization is an environmentally sound approach for addressing both of these problems. Review of two triple-crop systems revealed greater N and P recoveries for a corn silage-bermudagrass hay-rye haylage system, whereas forage yields and quality were greater for a corn silage-corn silage-rye haylage system, when manure was applied at rates to supply N. Nutrient uptake was lower than application during the autumn-winter period, and bermudagrass utilized more of the remaining excess than a second crop of corn silage. Economic comparison of these systems suggests that the added value of the two corn silage crop system was not enough to off-set its increased production cost. Therefore, the system that included bermudagrss demonstrated both environmental and economic advantages. Review of the N and P uptake and calculated crop value of various single, double, and triple crop forage systems indicated that the per hectare economic value as well as the N and P uptakes tended to follow DM yields, and grasses tended to out-perform broadleaf forages. Taken across all systems, systems that included bermudagrass tended to have some of the highest economic values and uptakes of N and P. Manure applied at rates to supply N results in application of excess P, and production will not supply adequate quantities of forage to meet the herd's needs. Systems that lower manure application and supply supplemental N to produce all necessary forage under manure application will likely be less economically attractive due to additional costs of moving manure further and applying it to greater land areas, but will be environmentally necessary in most cases. Intensive forage systems can produce acceptable to high quality forage, protect the environment, and be economically attractive. The optimal manure-forage system will depend on the farm characteristics and specific local conditions. Buffers and nutrient sinks can protect streams and water bodies from migrating nutrients and should be included as a part of crop production systems.

Double-cropping Winter Wheat and Soybean Improves Net Returns in the Eastern Great Plains

In the eastern Great Plains, winter wheat (Triticum aestivum L.) and different soybean [Glycine max(L.) Merr.] maturity groups (MG) are grown in various cropping systems to diversify crop production. A 10-year field study was conducted in southeastern Kansas to evaluate effects of multi-cropping systems on grain yield and net economic returns. Cropping systems evaluated were: (i) annual double-cropping of wheat and soybean (MG IV); (ii) four 2-year rotations of wheat-soybean double-cropped followed by full-season soybean the next year, where the same soybean MG (I, III, IV, and V) was grown both years; and (iii) a 3-year rotation of wheat, wheat, and full-season (MG V) soybean. On average, wheat yields ranged from 51 bu/acre following early MG I soybean in the 2-year double-crop rotation to 36 bu/acre following MG IV soybean in the annual double-cropping system. Wheat yield differences were primarily determined by planting date. Full-season (MG V) soybean yields were highest (35 bu/acre) following two years of wheat in the 3-year rotation. Double-crop soybean yields in the annual double-cropping system averaged 26 bu/acre for MG IV. Full-season and double-crop soybean yields in the 2-year double-crop rotation system were significantly greater for traditional MGs (III, IV, and V) than MG I. Net economic returns averaged $101/acre for annual double-cropping, which was $10 to $25/acre higher than 2-year systems with MGs III, IV, and V; whereas, net returns were lowest for the 3-year rotation ($51/acre) and for the 2-year system with MG I soybean ($44/acre).

Effects of cropping systems and microbial biomass on arylamidase activity in soils

The activity of arylamidase (EC 3.4.11.2) was recently detected in soils. This enzyme catalyzes the hydrolysis of an N-terminal amino acid from peptides, amides, or arylamides. Recent work suggests that this enzyme is involved in N mineralization in soils. The impacts of crop rotations and N fertilization on the activity of arylamidase were investigated in soils of two long-term cropping systems at the Northeast Research Center (NERC) in Nashua and the Clarion-Webster Research Center (CWRC) in Kanawha, Iowa, to assess the effect of the microbial biomass C (Cmic) and N (Nmic) contents on the activity of this enzyme. Surface soils (0–15 cm) were taken in 1996 and 1997 from four replicate field plots in corn, soybean, oats, or meadow (alfalfa) that received 0 or 180 kg N ha–1 before corn. Results showed that arylamidase activity was significantly affected by crop rotations in both years at the NERC site, whereas it was affected by N fertilization only in 1997. Because of the high degree of spatial variability and sampling time, no such relationship was found for the samples from the CWRC site. The greatest activity values were obtained in multi-cropping systems in meadow or oats, and the lowest values in continuous corn or soybean systems. The enzyme activity was significantly correlated with Cmic (r>0.40, P 0.56, P<0.001) in both years at the two sites. The amounts of N mineralized during 24 weeks of incubation at 30°C in soils of the plots receiving 0 or 180 kg N ha–1 were significantly correlated with arylamidase activity at the NERC site(r=0.88, P<0.001 and r=0.55, P<0.01, respectively), but not in soils from the CWRC site.

Characterization of active nitrogen pools in soils under different cropping systems

Studies were conducted to evaluate the relationships among different active N pools of organic matter in soils at two long-term cropping systems in Iowa. Results indicated that multi-cropping systems, particularly meadow-based systems, enhanced bioactivities of soils. Mono-cropping systems, particularly soybean, reduced soil microbial biomass and enzyme activities. The mineralizable N pool (potential N mineralization;No) was more sensitive to changes in the size of the microbial biomass N (Nmic) than to changes in organic N. One unit change in organic N did not lead to substantial changes in No, but 1 unit change in Nmic resulted in three or more units change in No. The active N pools and turnover rate were more sensitive to changes in organic C than to changes in microbial biomass C (Cmic). A unit change in organic C resulted in 10.6 units change in No, but a unit change in Cmic resulted in only 0.8 unit change in No. Cmic or Nmic are better indexes than organic C or N for the estimation of No or N availability, because biomass values are more highly correlated with cumulative N mineralized during 24 weeks of incubation, with r values ranging from 0.57 (P<0.001) to 0.88 (P<0.001).

Urease activity of microbial biomass in soils as affected by cropping systems

The impacts of crop rotations and N fertilization on different pools of urease activity were studied in soils of two long-term field experiments in Iowa; at the Northeast Research Center (NERC) and the Clarion-Webster Research Center (CWRC). Surface soil samples (0–15 cm) were taken in 1996 and 1997 in corn, soybeans, oats, or meadow (alfalfa) plots that received 0 or 180 kg N ha–1, applied as urea before corn and an annual application of 20 kg P and 56 kg K ha–1. The urease activity in the soils was assayed at optimal pH (THAM buffer, pH 9.0), with and without toluene treatment, in a chloroform-fumigated sample and its nonfumigated counterpart. The microbial biomass C (Cmic) and N (Nmic) were determined by chloroform fumigation methods. The total, intracellular, extracellular and specific urease activities in the soils of the NERC site were significantly affected by crop rotation, but not by N fertilization. Generally, the highest total urease activities were obtained in soils under 4-year oats–meadow rotations and the lowest under continuous corn. The higher total activities under multicropping systems were caused by a higher activity of both the intracellular and extracellular urease fractions. In contrast, the highest values for the specific urease activity, i.e. of urease activity of the microbial biomass, were found in soils under continuous soybean and the least under the 4-year rotations. Total and extracellular urease activities were significantly correlated with Cmic (r>0.30* and >0.40**) and Nmic (r>0.39** and >0.44**) in soils of the NERC and CWRC sites, respectively. Total urease activity was significantly correlated with the intracellular activity (r>0.73***). About 46% of the total urease activity of the soils was associated with the microbial biomass, and 54% was extracellular in nature.

Soil microbial biomass carbon and nitrogen as affected by cropping systems

The impacts of crop rotations and N fertilization on microbial biomass C (Cmic) and N (Nmic) were studied in soils of two long-term field experiments initiated in 1978 at the Northeast Research Center (NERC) and in 1954 at the Clarion-Webster Research Center (CWRC), both in Iowa. Surface soil samples were taken in 1996 and 1997 from plots of corn (Zea mays L.), soybeans (Glycine max (L.) Merr.), oats (Avena sativa L.), or meadow (alfalfa) (Medicago sativa L.) that had received 0 or 180 kg N ha–1 before corn and an annual application of 20 kg P and 56 kg K ha–1. The Cmic and Nmic values were determined by the chloroform-fumigation-extraction method and the chloroform-fumigation-incubation method, respectively. The Cmic and Nmic values were significantly affected (P<0.05) by crop rotation and plant cover at time of sampling, but not by N fertilization. In general, the highest Cmic and Nmic contents were found in the multicropping systems (4-year rotations) taken in oats or meadow plots, and the lowest values were found in continuous corn and soybean systems. On average, Cmic made up about 1.0% of the organic C (Corg), and Nmic contributed about 2.4% of the total N (Ntot) in soils at both sites and years of sampling. The Cmic values were significantly correlated with Corg contents (r≥0.41**), whereas the relationship between Cmic and Ntot was significant (r≤0.53***) only for the samples taken in 1996 at the NERC site. The Cmic : Nmic ratios were, on average, 4.3 and 6.4 in 1996, and 7.6 and 11.4 in 1997 at the NERC and CWRC sites, respectively. Crop rotation significantly (P<0.05) affected this ratio only at the NERC site, and N fertilization showed no effect at either site. In general, multicropping systems resulted in greater Cmic : Corg (1.1%) and Nmic : Ntot (2.6%) ratios than monocropping systems (0.8% and 2.1%, respectively).

A PC model for selecting multicropping farm machinery systems

A model, Computed Farm Machinery System (ComFARMS), has been developed to analyse mechanisation problems of Italian arable farms (<250 ha) from strategic and management standpoints. The article mainly describes the model's strategic approach to multicropping farm machinery selection. Once a given crop rotation pattern and a list of operations per crop are put in, the selection offers the user a machinery set (tractors and implements) where each machine is defined in terms of type, number and size. This selection may regard only a part of the machinery set. The main model algorithms are discussed with numerical examples. Selection can be carried out by performing search and/or optimisation techniques. A run example related to a typical Italian five-year rotation is finally presented. ComFARMS can be run by researchers and policy makers to explore different agricultural mechanisation scenarios. It is being incorporated in a more general decision support system to improve its use by farmers and advisors at farm level as well. ComFARMS is also implemented on a PC running Microsoft Windows.

Insect Management in Reduced Tillage Systems

Adoption of reduced-tillage methods of crop production has been extraordinarily rapid, especially in states with rolling topographies. According to Phillips (1974) corn and soybean no-till acreage in Kentucky increased from 110,000 to 650,000 from 1969 to 1974, respectively. This cultural method and its value in development of multicropping systems have created many entomological problems.